Maryland Rain Garden Manual


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Maryland Rain Garden Manual

  1. 1. ain ardens Across MarylandCleaning Maryland’s waterways one rain garden at a time.
  2. 2. PrefaceIntroduction Small-scale practicesIf you enjoyed reading Rain Gardens in Maryland’s Small-scale practices capture and treat stormwaterCoastal Plain, you will enjoy reading Rain Gardens runoff from impervious areas usually less than oneAcross Maryland. This new and improved “how-to” acre in size. These practices typically include naturalmanual discusses the benefits of incorporating systems, vegetation, and soils and may bemultiple small-scale practices into a rain garden interconnected to create a more natural drainagedesign. You will also learn how to: system. Although this manual focuses on installing rain gardens, the ESD strategy requires that  Reduce impervious surfaces stormwater management practices, including the  Size your rain garden to capture the small-scale practices listed below, be integrated into maximum rainfall amount one project to the maximum extent practical. Small-  Select rain garden plants native to Maryland scale practices include:  Install rain barrels  Measure your rain garden’s performance  Rain gardens  Rainwater harvesting  Submerged gravel wetlandsEnvironmental Site Design  Landscape infiltration  Infiltration bermsFor homeowners required to install stormwater  Dry wellsmanagement practices, this manual provides  Micro bioretentionenvironmental site design, or ESD sizing criteria for  Swalesrain gardens. Just look for “ESD criteria” text  Enhanced filtersboxes. The ESD criteria outlines the minimumrequirements homeowners shall implement in order tosatisfy Maryland’s stormwater regulations and shouldbe approved by your local approving authority before Stormwater Design Manualyou begin building your rain garden. Homeowners The primary goal of Maryland’s stormwaterinstalling rain gardens voluntarily do not have to meet management program is to maintain predevelopmentESD criteria. runoff characteristics as nearly as possible. The ESD criteria provides a comprehensive design strategy toTitle 4, Subtitle 201.1(B) of the Stormwater achieve this goal and is described in Maryland’sManagement Act of 2007 defines an ESD as using Stormwater Design Manual. To learn more about thesmall-scale stormwater management practices, Maryland Department of the Environment’s approvednonstructural techniques, and better site planning to rain garden ESD sizing criteria and other approvedmimic natural hydrologic runoff characteristics and small-scale practices, refer to chapter 5 of theminimize the impact of land development on water Maryland Stormwater Design Manual, “Environmentalresources to the maximum extent practical. Under Site Design.” This document can also be found atthis definition, ESD includes:  Minimizing impervious surfaces WaterPrograms/SedimentandStormwater/  Conserving natural features e.g., drainage swm2007.asp. patterns, soil, vegetation  Slowing down runoff to maintain discharge timing and to increase infiltration  Using other nonstructural practices or innovative technologies approved by the Maryland Department of the Environmentii
  3. 3. Table of ContentsIntroduction ................................................................................... 1Location ............................................................................................. 5Sizing ................................................................................................. 9Rain Garden Sizing Worksheet ................................................... 14Construction ..................................................................................... 17Planting .............................................................................................. 23Maintenance ..................................................................................... 29Rain Garden Checklist.................................................................... 32Appendices ....................................................................................... 33References ....................................................................................... 44Acknowledgements ......................................................................... 45Special Thanks................................................................................. 47 iii
  4. 4. Figure 1. As runoff passes through the soil mixture, chemical and biological processes break down the pollutants. This helpsprotect the Atlantic Coastal and Chesapeake Bays from fertilizers, oils, and other pollutants carried by runoff.
  5. 5. IntroductionFigure 2. Rain gardens absorb rainwater flowing from roofs, lawns and other impervious surfaces.Homeowners across Maryland are ESD Criteria # 1. Definitionimproving water quality, reducing A rain garden is a shallow, excavatedflooding, and increasing their property landscape feature or a saucer-shapedvalues by adding rain gardens to their depression that temporarily holdslandscape (figure 2). A typical rain runoff for a short period of time. Raingarden consists of a shallow depression gardens typically consist of anthat is a planting bed of native plants, absorbent-planted soil bed, a mulchloose soil, mulch, and sometimes stone. layer and planting materials such asTogether, these elements collect, shrubs, grasses and flowers (figure 1).absorb, and clean runoff. An overflow conveyance system isWell designed rain gardens collect and included to pass larger storms.soak up rainwater that flows off of Captured runoff from downspouts,hard surfaces. Commonly referred to roof drains, pipes, swales, or curbas stormwater runoff, the rainwater openings temporarily ponds and slowlyspreads throughout the rain garden. As filters into the soil over 24 to 48the stormwater runoff passes through hours.the soil mixture, physical and biological Source: Maryland’s Stormwaterprocesses such as plant uptake and Management Act of 2007,adsorption to soil particles remove Environment Article 4 §201.1 andpollutants and nutrients in stormwater §203. ff.runoff (figure 1). Introduction 1
  6. 6. Your rain garden(s) can help infiltrate 100% of the runoff in your drainage area with proper planning. That’s less runoff entering storm drains that eventually flow into our waterways and ultimately the Atlantic Coastal and Chesapeake Bays (figure 3). In addition to cleaning our waterways, rain gardens also help:  Replenish groundwater resources  Protect structures and landscaping  Enhance the beauty of yards  Provide wildlife habitat You can contribute to cleaner water by building a rain garden in your landscape. By using this document to help guide you through the rain garden planning and building process, you will learn how to:  Locate your rain garden  Size your rain garden  Build your rain garden  Select native plants  Maintain your rain garden ESD Criteria # 2. Micro-scale Practice Rain gardens can be primary or secondary practices on residential, commercial, industrial, or institutional sites. This practice is typically used to treat runoff from small impervious areas like rooftops, driveways and sidewalks. Rain gardens can also beFigure 3. When hard surfaces prevent rainwater from used in retrofitting and redevelopmentseeping into the ground it will flow into drain systems applications and in a series wherecarrying with it pollutants and nutrients. Thestormwater, if left untreated, can harm our local existing slopes require energystreams, creeks, rivers, and lakes and everything dissipation.dependent on clean healthy waterways.2 Introduction
  7. 7. Rain Garden FactsDoes a rain garden form a pondor wetland?No. The rainwater will soak into theground within 24-48 hours after astorm (figure 4).Will a rain garden become a Figure 4. Don’t be surprised if your rain garden hasmosquito breeding ground? water in it after a storm. It’s supposed to. The rain garden installed across from the town hall in HighlandNo. Mosquitoes lay eggs in standing Beach, Maryland is strategically placed to collect runoffwater. Rain gardens do not hold from the road and lawns.rainwater long enough for mosquitoesto reproduce successfully (figure 5).Does a rain garden require a lotof maintenance?No. Established native plants requireno more maintenance than any othertype of garden. Native speciesgenerally require less maintenance ifthey are planted in the right place.They do not need fertilizers, Figure 5. The rain garden installed across from thepesticides, or additional water other Highland Beach Town Hall drains water after eachthan what nature provides (unless storm. Well designed rain gardens drain 24-48 hours after a storm.there is a severe drought).Is a rain garden expensive tobuild and maintain?No. With any gardening project, thecost is related to the location, size,labor, tools, supplies and materials, andplants. To keep the costs low, invitefamily and friends to help build therain garden (figure 6) and buyperennials. Your one-time investment Figure 6. Sweat equity cuts costs. Shown above,will come back each growing season. volunteers install a shade rain garden at the Chesapeake Ecology Center in Annapolis, Maryland. Introduction 3
  8. 8. Figure 7. Identify existing landscaping features relative to your house to help locate the best place to build your rain garden. Thiscan help you capture runoff from impervious surfaces and improve your landscape.
  9. 9. LocationThis section explains how to locate ESD Criteria # 3. Locationyour rain garden by answering the Lot-by-lot use of rain gardens is notfollowing questions: recommended in residential 1. What elements should you subdivisions due to subsequent removal consider when choosing a by homeowners. If used on a lot-by-lot location for your rain garden? basis, educating the homeowners will 2. What type of soil do you have? be needed to prevent removal. An 3. What shape should it be? educational sign similar to the one shown below in figure 8 is helpful. Rain garden excavation in areas with heavy1. Where? tree cover may damage adjacent treeTo determine where to build your rain root, you will need a goodunderstanding of the layout of youryard. To begin, identify existinglandscaping features and hard surfaceslike the driveway, any outbuildings, andhouse (figure 7). Map these featureson paper to help you begin envisioningwhere a rain garden could be built.Consider the tips below to help youchoose the best rain garden location.  When it rains, watch the flow of water on and around your property. Using arrows, draw Figure 8. Install rain garden signs to raise the movement of water from awareness. your house or driveway (both going away from or toward your ESD Criteria #4. Infrastructure house). You’ll begin to see the The location of existing and proposed direction runoff flows towards buildings and utilities (e.g., water storm drains or waterways. supply wells, sewer, storm drains, Locate your rain garden so that electricity) will influence rain garden it intercepts the runoff before design and construction. Landscape flowing into these outlets. designers should also consider  Low-lying wet areas where overhead telecommunication and water naturally ponds after a electrical lines when selecting trees to heavy storm may be good areas be planted. Read the “Construction” for your rain garden too. section to learn more (pages 17-21). Location 5
  10. 10. Figure 9. The rain garden installed more than 30 feet from the house has a larger drainage area than the gardenlocated within 30 feet of the house. The farthest garden will likely capture and treat more runoff.  The best location for the rain crawl spaces. Check with your garden is in partial to full sun. local approving agency for  Locate rain gardens downslope additional guidance. from a downspout, driveway or  Level or gently sloping sites other impervious surfaces to require the least amount of capture and treat more runoff digging. (figure 9).  Think about the views of your  Rain gardens should be at least rain garden within the existing 25 feet away from a septic landscape from different drain field or well head and 10 perspectives, including inside feet away from a dwelling the house. foundation to prevent water from seeping into basements or 1. Your rain garden is _____ feet from the . (impervious surface)ESD Criteria # 5. Soils 2. Identify soil typeClay soils or soils that have beencompacted by construction equipment Check the soil type of your rain gardengreatly reduce the effectiveness of site before you begin digging. Your soilrain gardens. Loosening of compacted type influences the garden’s drainagesoils may improve drainage capability. and size. If your rain garden is sandy,6 Location
  11. 11. Figure 10. A quick sketch can help you visualize the garden’s location. Its longest side should be oriented tointercept runoff flowing downhill and from any direct sources of runoff like a downspout.then you have the best drainage and select another rain garden location. Ifcan build the garden smaller than those you are unsure about your soil type,built on clay or silt laden sites. refer to appendix A for other types of soil tests.To identify your soil type put some soilin your hands. If the soil feels gritty 2. Your soil type is sand silt or clay.and coarse, it’s probably sandy soil.Silty soil, however, feels smooth but 3. Shapenot sticky. Clay soils are very stickyand plastic-like to handle when wet. Once you’ve picked out the location forYou’ll be able to form a ball with it. A your rain garden, determine its shape.visual inspection can also indicate the Your rain garden can be any shape—soil type at your site. If you still have crescent or kidney shapes arestanding water 24 hours after a rain attractive—but a long and narrow rainevent then you probably have some clay garden works well if you are placing itsoils at the site. between structures, such as a driveway and patio. Long rain gardens canRain garden areas high in clay content capture the greatest amount of runoffmay require you to amend the native if located properly (figure 10).soil with a rain garden planting soilmixture (read pages 20 and 21 for 3. Your rain garden’s shape is a .more information). Another option is to Location 7
  12. 12. Figure 11. Make sure your rain garden surface ponding depth is deep enough to hold runoff, allowing it to gradually soak into thenative soils.
  13. 13. SizingFigure 12: Your drainage area may include impervious surfaces like portions of the lawn (highlighted in blue), roof,sidewalk, and driveway (highlighted in red). These elements can direct more stormwater runoff into rain gardens.This section provides guidance on 1. Impervious surfacessizing your rain garden to capture at Impervious surfaces in your drainageleast 70% of the runoff for the area prevent water from seeping intoaverage yearly rainfall. In Maryland, the ground, thereby increasing thethe annual average rainfall is 42 inches. amount of stormwater runoff capturedTo capture 100% of the runoff from a in your rain garden. The rain garden,specific storm event, refer to shown in figure 12, is located less thanappendix B to determine your rainfall 30 feet from a roof downspout and hasdepth. You can skip to page 15 to a drainage area that includes thedetermine how to size your garden portion of the roof that feeds thebased on targeting a rainfall amount. downspout and any ground level hardReading through this section, however, surfaces that slope to the rain garden.will help you understand what you willneed to consider when sizing your rain ESD Criteria # 6. Treatmentgarden. You can adapt these guidelines The rainfall amount used to size ESDto meet your site’s unique conditions practices shall be applied to theand personal water quality goals. Read contributing drainage area. ESDfurther to learn about these topics: practices shall be used to treat the 1. Impervious surfaces runoff from one inch of rainfall on all 2. Improving your drainage area new developments where stormwater 3. Sizing your rain garden management is required. 4. Quantifying performance Sizing 9
  14. 14. Figure 13. Permeable pavers installed at the Back Creek Nature Park in Annapolis, Maryland provide a solid groundsurface that can support vehicles.The rain garden located more than 30 benefits of permeable pavers andfeet from the house can capture more permeable concrete include:runoff because of the increased  Increased groundwateramount of impervious surfaces, recharge and/or storage,including the lawn (which can be thereby lessening surfacepartially impervious), deck, roof, puddles and local flooding.sidewalk, and driveway.  Reduced stream bank erosion and downstream flooding.2. Improving your drainage area  Capturing of nearly 100% of polluted runoff depending onConsider reducing impervious surfaces project design parameters,on your property to reduce the amount thereby mitigating impact onof runoff entering your rain garden by surrounding surface waters.replacing asphalt with permeable  Decreased project cost bypavers or permeable concrete. They reducing retention/detentionprovide a solid ground surface, strong systems and runoff.enough to take heavy loads, like large  Minimization of impacts andvehicles, while at the same time stress on existing storm sewerallowing water to filter through the systems through reduced peaksurface and reach the underlying soils discharges.(figure 13). Permeable pavers are also  Reduced heat island effect andideal for patios, sidewalks, and thermal loading on surroundingdriveways. The voids in the surface of surface waters.the paving allow water to drain throughand into the soil beneath. Other10 Sizing
  15. 15.  Faster snow melt on permeable pavement and drains, reducing winter ice hazards, deicing salt use, and snow removal costs.Another way to improve your drainagearea is to divert flows away fromimpervious surfaces. This is known asnon-rooftop disconnection. Simplydirect flow from impervious surfacesonto vegetated areas, where it cansoak into or filter over the ground. Figure 14. In the example above, the roof is about 60This will disconnect these surfaces feet by 40 feet. The total roof area is 2,400 ft2.from the storm drain system, reducingrunoff volume and pollutants deliveredto waterways.Non-rooftop disconnection is commonlyapplied to smaller or narrowerimpervious areas like driveways, opensection roads, and small parking lotsand depends on several site conditions(e.g., permeable flow path length, soils,slopes, compaction) to function well. Figure 15. In the example above, about 25% of the total roof area feeds water to the downspout.Consider how you can improve yourdrainage area as you work through the 1. Estimate the total roof area (infollowing calculations that will help square feet), roof area=lengthdetermine your rain garden’s size. x width (figure 14). 2. Estimate the percentage of roof feeding the downspout3. Dimensions (figure 15). 1. The roof drainage area (RDA)To determine the dimensions of yourrain garden, you’ll need to do a little equals the total roof area multiplied by the percentage ofmath to assess the following: roof feeding a downspout 3a. Drainage area (see sample calculation below). 3b. Ponding depth 3c. Rain garden area RDA = (40’ x 60’ ) x 25% RDA = 2,400 ft2 x 25% 3d. Width and length RDA = 600 ft23a. Calculate drainage area 4. Calculate the ground surfaceThe following five steps will help you area draining to the site bydetermine your drainage area. multiplying its length and width. Sizing 11
  16. 16. ESD Criteria # 7. Target rainfall Be sure to include all impervious surfaces that drain to yourDuring the project planning and garden. Break the total areapreliminary design, site soils and into rectangles for easyproposed imperviousness are used to calculations.determine target rainfall for sizing 5. The sum of the ground surfaceESD practices to mimic wooded area and roof drainage areaconditions (refer to page 15). equals the total drainage area.ESD Criteria # 8. Drainage Area 3a. Your drainage area is ______ ft2.A rain garden’s drainage area serving a 3b. Determine ponding depth & slopesingle lot in a residential subdivision Your rain garden’s surface pondingshall be 2,000 ft2 or less. The depth, as shown in figure 11 on page 8,maximum drainage area for all other depends on your site’s slope. Toapplications shall be 10,000 ft2. Micro- determine your slope, you will need abioretention or bioretention should be level and to do a little math. Read all ofconsidered when these requirements the instructions below beforeare exceeded. beginning. Figure 16 may also help youESD Criteria # 9. Topography visualize the instructions below.Rain gardens require relatively flat 1. Securely drive a stake on theslopes (<5%) to accommodate runoff uphill side near the mid-point offiltering through the system. Some the garden’s top edge. Drive adesign modifications can address this second stake just past theconstraint through the use of downhill edge of the site. Theinfiltration berms, terracing, and downhill stake must be talltimber or block retaining walls on enough to tie the string in themoderate slopes. next step. 2. Tie stretchy string near theESD Criteria # 10. Treatment bottom of the uphill stake. The string should not touch theThe surface area of rain gardens shall ground or other objects. Using abe at least 2% of the contributing string level or carpenter’s level,drainage area. The rainfall target level the string from the uphillvalue shall be applied to the stake to the downhill stake.contributing drainage area (refer to 3. Measure the string’s lengthpage 15). Temporary storage of the (in inches) between the stakes.runoff volume may be provided above 4. Measure the height (in inches)the facility with a surface ponding of the downhill stake from thedepth of 6 inches or less (see figure 11 string to the ground.on page 8) . 5. To calculate the slope of your site, divide the height by the12 Sizing
  17. 17. Figure 16: A rain garden with a 5% slope (shown above) should have a surface ponding depth of 5 inches (table 1below). A surface ponding depth of 9 inches will allow for 3-4 inches of a topping layer. string’s length and multiply the more depth, inch for inch, if you plan result by 100. A sample to spread mulch on the surface. If you calculation is provided below. have a more sloping site, you may need to remove or add soil to create a level Slope % = (9”/180”) x 100 base. Circle the proposed depth below. Slope % = 0.05 x 100 Slope % = 5% 3b. Ponding depth: 5” 6-7” 8” (circle one) Slope: % add mulch layer (if any) inches. 3c. Determine rain garden areaUse table 1 below to determine yourgarden’s surface ponding depth. Add Use the sizing worksheet on the next page to determine your rain garden’s Slope Surface Ponding area. If you decide that the area is too Depth big consider breaking up the garden area into two or three smaller gardens.Less than 5% 5 inches deep If you discover that your garden is tooEqual to or greater 6-7 inches deep small to hold the amount of waterthan 5-7% flowing into it create an overflow areaEqual to or greater ~8 inches deep (e.g., with stone) to relieve excessthan 7-12% water or create a system ofEqual to or greater Select another site or talk interconnected rain gardens. Morethan 12% to a professional than one rain garden can be installed to landscaper better disperse and absorb runoff.Table 1. Slope and ponding depth reference table. Sizing 13
  18. 18. Rain Garden Sizing Worksheet Insert your answers from the previous pages to determine your rain garden’s dimensions.  Garden’s distance from impervious surface(s): (page 6)  Soil type: (page 7)  Shape: (page 7)  Drainage area: ft2 (page 12)  Total surface ponding depth: inches (page 13)  The size factor is (see table 2 below) Rain Garden Surface Ponding Depth Soil type 5” 6-7” 8” All depths Sand 0.19 0.15 0.08 0.03 Size Silt 0.34 0.25 0.16 0.06 factor Clay 0.43 0.32 0.20 0.10 Less than 30 feet More than 30 feet Distance from downspout Table 2. In the table above, the size factor is determined by three items: the rain garden surface ponding depth, soil type, and distance from the downspout. To determine the size factor for your rain garden, locate the intersection of these three items in the table above. For example, a rain garden that has a surface ponding depth of six inches, contains sandy soils, and is less than 30 feet from a downspout has a size factor of 0.15. A rain gardens installed more than 30 feet away from a downspout and has sandy soils will have a size factor is 0.03 regardless of its surface ponding depth.  Rain garden area = ft2 Rain garden area = drainage area x size factor  Width = feet (page 15)  Length = feet14 Sizing
  19. 19. Figure 17. The shortest side should be 4-10 feet wide to balance the effect of slope with the rain garden depth andis best placed perpendicular to the slope. For lawns with a slope greater than 8%, the maximum recommendedwidth is 15 feet.3d. Determine length and width Following, you will learn how to buildEstimating the rain garden length your rain garden based on a rainfall(longest side) and width (shortest side) amount and calculate your drainageis based on your garden area, personal area’s recharge volume.preferences, and a little bit of math. 1. Target rainfallTo begin, estimate how wide your Maryland’s environmental site designgarden should be by considering your criteria for sizing rain gardens aregarden’s shape and unique site based on capturing and retainingconditions. This includes the available enough rainfall so that the runoffyard space, the distance between leaving a site is reduced to a levellandscaped areas, and any physical equivalent to a wooded site in goodconstraints. By considering these condition. To estimate the amount ofelements, you may decide that your rainfall treated by your rain gardengarden should be 5 feet wide (figure use the formula below.17). You’ve just selected the width ofyour garden. Use the selected width inthe sizing worksheet on the oppositepage to calculate the garden’s length. If you would like to capture 100% runoff, refer to appendix B for your4. Performance measures local rainfall depth and considerWith a little bit of math work, you can installing other small-scale practicesquantify the impact your rain garden discussed on pages 9 to 11 to improvehas on capturing stormwater runoff. your drainage capacity. Sizing 15
  20. 20. Recharge Volume (watershed-inches) A soils B soils C soils D soils Site Imperviousness (%)Figure 18. Use the line graph above to plot your site’s imperviousness and recharge volume. For example, if yourrecharge volume equals 0.15 and your site imperviousness equals 20% you are above the minimum rechargevolume for all HSG soils. However, if your site imperviousness is 90% you do not meet the minimum rechargevolume for HSG A or B soils. Additional small-scale practices may be necessary to achieve the site’s rechargevolume. Source: Maryland Stormwater Design Manual, “Unified Stormwater Sizing Criteria”, p 2.6.2. Recharge volume be recharged into the groundwater.Impervious surfaces prevent rainfall Recharge volume is based on thefrom percolating into the ground, hydrologic soil groups (HSG) at thereducing the amount of groundwater site, and the amount of imperviousrecharge. This change alters the cover created by the development.natural hydrology of stream and Follow the next steps to calculate thewetland systems and harms the habitat recharge volume.of many aquatic organisms. Exceeding 1. Referring to table 3, classify yourthe minimum recharge volume attempts soil type within a HSG andto reverse this impact by requiring identify the HSG soil specificthat a specific amount of stormwater recharge factor (SSRF). 2. Calculate the drainage area’s HSG - Description SSRF imperviousness (I). A ~ excessively drained 0.38 B ~ well drained 0.26 C ~ moderately well drained 0.13 3. Calculate the recharge volume. Recharge volume = SSRF X I D ~ somewhat poorly drained 0.07 4. Plot your drainage area’sTable 3. Consult chapter 2 of the Maryland StormwaterDesign Manual, “Unified Stormwater Sizing Criteria”, imperviousness on the line graphand chapter 3 of the Natural Resources Conservation above to evaluate the rechargeService Soil Survey Manual, “Examination and volume (figure 18).Description of Soils”, for details.16 Sizing
  21. 21. ConstructionFigure 19. A sketch of your rain garden can help guide the construction process. In the example above, the raingarden is about 4-8 feet wide and has a surface ponding depth of 5-6 inches. Rocks located at the entrance pointhelps to dissipate runoff and the berm helps to hold water in the rain garden.In this section, you will learn how to  For a self-installed rain garden,prepare the site and dig your rain expect to pay between $3 andgarden. To help guide you through the $5 per square foot in plant costsconstruction process sketch out the and soil amendments. Whengarden’s dimensions and surroundings. working with a landscapingA sketch similar to figure 19 is an company to design and installexample that can help you during your rain garden, the cost willconstruction.Preparing the site ESD Criteria # 11. InspectionTo avoid digging on or near utility lines Regular inspections shall be madeor pipes, contact Miss Utility at during the following stages of1-800-257-7777 or construction.48 business hours prior to digging. To  During excavation to subgradebe on the safe side, you may consider and placement of planting soil.contacting Miss Utility one week prior  Upon completion of final gradingto digging. The following tips will also and establishment of permanenthelp you prepare your site for digging. stabilization. Construction 17
  22. 22. Figure 20. Bay-Wise master gardeners installed a rain garden at the Chesapeake Ecology Center in Annapolis, MD.ESD Criteria # 12. Conveyance significantly increase to around $10 to $15 per square foot.Runoff shall enter, flow through, and  Depending on your rain gardenexit rain gardens in a safe and non- size you may want additional helperosive manner. (figure 20). Building an average-ESD Criteria # 13. Internal slope size rain garden can take one person several hours, while aA minimum internal slope of 1% should team of friends or neighbors canbe maintained and a shallow berm dig a rain garden in a fraction ofsurrounding the rain garden is the time. With more friends it’srecommended to avoid short- also twice as much fun.circuiting. For sloped applications, a  At the site use a flat shovel toseries of rain gardens can be used as peel the grass away from the“scalloped” terraces to convey water soil. You might be able to reusenon-erosively (refer to pages 12-13). the sod to build a vegetated berm.ESD Criteria # 14. Erosion &  If the grass is too tough to peel,Sediment Control cover it with black plastic untilRain gardens shall not be constructed the grass dies. This usually takesuntil the contributing drainage area is 3-4 weeks. Pesticides should onlystabilized. During construction, runoff be used as a last resort as thisshould be diverted and the use of could harm pets, local wildlife,heavy equipment avoided to minimize and nearby plants.compaction.18 Construction
  23. 23. Figure 21. Creating a curb cut allows stormwater runoff from streets to enter rain gardens.  If possible, plan to install your the garden’s edge (figure 23 on page rain garden in the late spring or 20). Another way to mark the edge is fall when the soil will be easier to mow the shape of your garden. If to dig and when the plants are you decide to do so, make the corners more likely to thrive. gentle, otherwise they will be difficult to mow. Remove and replace the stakes when you are done mowing (refer toExcavation page 12). You’ll need the stakes forFollow the steps below to begin digging building a berm. The edge between cutyour rain garden. and uncut grass will give you an easy to1. Capturing runoffBe sure the runoff sources will flow tothe garden site. If your rain gardenwill receive runoff from roadways,make sure curb cuts are created(figure 21 and 22). This assuresrainwater will flow into the garden.2. Outlining the rain garden shapeWhile referring to your sketches, layout the approximate shape of your raingarden with marking paint, heavy rope,or a hose. You can also use surveyor Figure 22. A curb cut allows runoff to flow into a rainflags or overturn the grass to mark garden at Heritage Baptist Church in Annapolis, MD. Construction 19
  24. 24. maintain shape. Be creative with the shape, but gentle curves look the most natural. 3. Constructing the berm A berm is a low soil mound constructed along the width and downhill side of your rain garden. Its top should be about level with the uphill side and its base should be a foot or more wide with gently sloping sides. Berms on the downhill side of a garden are necessary on sloping sites. This will help hold water in your garden giving it time to seep into the soil. To build your berm, consider reusing the sod and soil from your rain gardenFigure 23. The Lower Eastern Shore Tributary Strategy area (figure 24). This will help create aTeam outlines the garden’s shape by marking it withpaint and overturning sod. vegetated berm which is more likely to withstand berm erosion. 4. Soil mixture (optional) Amend soil only if necessary. If you are planning to remove existing soil in order to add rain garden soil mixture, make sure you dig a few more inches below the garden base (refer to figure 16 on page 13). A soil mixture consisting of 50-60% sand, 20-30% topsoil (no clay), and 20-30% compost will help establish plants and allow water to soak in. Use the formula below to help estimate the amount of total fill needed for your garden. Fill = width x length x depth below garden baseFigure 24. To construct the rain garden at the WardMuseum of Wildfowl Art in Salisbury, Maryland, the Follow the ESD criteria #15 if you areLower Eastern Shore Tributary Strategy Team reused required to implement stormwaterthe garden area’s sod to build a vegetated berm alongthe downslope side of the garden. management by your local approving authority.20 Construction
  25. 25. Figure 25. If your level is long enough, use it to level the height of your rain garden berm.5. Putting it all together flowering perennials (flowers andReferring to your sketches, you will grasses) or woodies (shrubs and trees)know how deep to dig. If your ponding in your garden. Read the next sectiondepth is 6 inches, you will remove all to learn how to select and install nativethe sod and soil 6 inches below the plants in your rain garden.level string line. Remember to dig a fewmore inches if you are adding mulch, ESD Criteria # 15. Planting Soilcompost, or soil. Planting soil should be mixed on–site prior to installation. If poor soils areBegin digging at the uphill side near encountered beneath the rain garden,the stake and place the dirt (and sod) a four–inch layer of washed gravel (1/8in the berm location. Level the berm’s to 3/8 inch gravel preferred) may beheight with the uphill side by eye- used below the planting soil mix. Theballing it, moving the downhill stake planting soil and mulch shall conformalong the lower edge of the rain garden to the specifications found in appendixwhile making sure the string is level, or B.4 of the Maryland Stormwaterby placing a carpenter’s level on a Design Manual atstraight 2x4 that reaches from the side to the berm (figure 25). WaterPrograms/Now that the rain garden is dug you SedimentandStormwater/are ready to plant herbaceous stormwater_design/index.asp. Construction 21
  26. 26. Marsh Marigold Spiderwort Tall White BeardtongueFigure 26. Rain gardens add color and life to your landscape.Swamp Milkweed Blueflag Iris Blueberry Bush
  27. 27. PlantingFigure 27. Sketch out your basic rain garden design. You don’t have to be an architect!With the grunt work done, you’re now ESD Criteria # 16. Designready to bring your rain garden to life Landscaping plans shall clearly specifywith your native plant selection (figure how vegetation will be established and26). In this section, you will learn how managed. A rain garden should beto select plants, lay out a rain garden located in full to partial sun, at leastdesign, install plants, and apply mulch. two feet above the seasonal high water table and have a total rainRain garden design garden depth of 12 to 18 inches (refer to figure 11 on page 8). Plants selectedCreate a sketch of your rain garden for use in the rain garden shoulddesign to help guide your plant tolerate both saturated and dryselection (figure 27). To help you conditions and be native or adapted tobrainstorm, refer to appendix C for a Maryland. Neatly trimmed shrubs, asample design and review the tips crisp lawn edge, stone retaining walls,below. and other devices can be used to keep  For a bold impact, reduce the a rain garden neat and visually amount of space between plants appealing. by a few inches from the Planting 23
  28. 28. Figure 28. Clustering creates the visual impact in the rain garden along Lincoln Drive in Annapolis, MD. recommended spacing. This for Wildlife Habitat and Conservation allows mature plants to overlap. Landscaping: Chesapeake Bay  Plant your native shrubs and Watershed,, and flowers where their unique The Low Impact Development Center textures, colors, and heights will also provide helpful tips on how to complement one another and choose the plants for your garden and help achieve the desired visual provides pictures of them too. Below impact. Like grade-school are some tips to help you select plants. pictures, tallest in the back and shortest up front. Sun, partial sun, and shade Select native plants adapted to the sunlight your rain garden will receive.Plant SelectionNative plants create habitat suited for Height, color, and texturewildlife, grow well without chemical The physical properties of your plantssupplements, and require less will help add variety and interest tomaintenance. With native species, your your rain garden. If your rain gardenrain garden will be beautiful, healthy, lacks flowering blooms, then takeand safely enjoyed by insects, birds, advantage of different leaf shades,pets, and children. Decide which native shapes, and colors. For example,plants meet your personal preferences combining a variety of textures,by referring to appendix D for a list of staggering heights, and plants bearingnative plants or visit your local nursery. variegation increases visual interest ifOnline resources like the Native Plants clustered properly (figure 28).24 Planting
  29. 29. Figure 29. White Turtlehead. Figure 30. Baltimore Checkerspot Butterfly.Cluster RootsLike real estate, landscaping has three Buy one or two-year old plants withrules: cluster, cluster, and cluster. Buy well-established root systems that areat least three individual plants of each beginning to circle or mat the pot, yetspecies, but seven is typically the are young enough to adapt well to newminimum number for a cluster. growing conditions.Blooms Incorporating clusters of ferns,Design your rain garden to be “alive” rushes, and grasses with yourspring through fall by selecting plants flowering plants creates good rootthat bloom throughout the seasons. competition. This is normal and causesFor example, beardtongue blooms from a healthier root pattern to develop.April to June and cardinal flower, a Blending a mix of clustered planthummingbird favorite, blooms from species reduces the chance of theJuly to September (see front cover). garden being overrun by one species.White turtlehead (figure 29) blooms If you would like to plant shrubs andfrom August to October and is the only trees, make sure they are well adaptedplant that the Maryland state insect, to at least part-time wet conditions.the Baltimore Checkerspot Butterfly,will lay its eggs on (figure 30). By Plant!designing your garden to bloom year While referring to your rain gardenround with native plants, local insects design sketch, place the potted plantsand wildlife will benefit too. in your rain garden. Try to visualize them full grown and move them around Planting 25
  30. 30. Figure 31. Lower Eastern Shore Tributary Team members and volunteers planted native grasses, flowers, andshrubs at one of two rain gardens installed at the Providence Presbyterian Church in Salisbury, MD.ESD Criteria # 17. Landscape until you’ve reached the best effect. Be bold, but cluster! The following tipsInstallation will help you begin planting your pottedThe optimum planting time is during plants.the Fall. Spring planting is also  Dig each hole so it is at leastacceptable but may require watering. twice as wide as the pot and noESD Criteria# 18. Conveyance deeper than the pot. You will know if the hole is deep enoughRunoff shall enter a rain garden at the when the pot’s soil and thesurface through grass swales and/or a plant’s crown are level with thegravel bed. Energy dissipation shall be existing grade.provided for downspout discharges  Plant one plant at a time fromusing a plunge area, rocks, splash one side to the other or fromblocks, stone dams, etc. the middle out to avoid stepping on plants.ESD Criteria # 19. Treatment  Remove the plants by tapping  A minimum layer of 6-12 inches the side of the pots to loosen of planting soil shall be provided them. Do not expose plant roots (refer to figure 11 on page 8). any longer than necessary.  A mulch layer 2-3 inches deep  Loosen the matted roots circling shall be applied to the planting with the shape of the pot. soil to maintain soil moisture and to prevent premature clogging.26 Planting
  31. 31. Figure 32. The rain garden above, designed by Kara Bowne Crissey and installed by the Severn Grove EcologicalDesign, placed rocks along the edge to dissipate runoff during storm events.  Place the plant in the hole, fill at a depth of about one quarter of the hole with soil, and firmly their height. tamp it. Another option is adding organic  Water your plants immediately. matter, such as shredded leaf mulch,  To help remember what’s what, to improve soil structure. It also put plant labels next to each conserves moisture, blocks light that cluster. many weed seeds need to germinate,With the helping hand of a friend, you lessens erosion, and is an attractivewill be able finish in an hour or two top dressing for your planting bed.(figure 31). Once all are planted, roundup your pots and either reuse or As a rule-of-thumb, apply mulch to arecycle them. depth of 2-3 inches in planting beds. The depth of mulch to apply will depend upon the type of material used.Toppings: stone and mulch Be sure not to bury seedlings orUntil the native plants can establish dormant plants, and keep it a fewthemselves, spread stone across the inches from the trunks of trees andentrance point of your rain garden to shrubs. Commonly used organic mulchesslow water flow (figure 32). This will include: chipped or shredded woodalso help prevent strong storm events mulch, such as pine or cypress; pinfrom washing out the mulch, soil, or needles; and shredded leaves.breaking through the berm. To look Inorganic mulches include: gravel andmore natural, stones should be buried other types of stone. Planting 27
  32. 32. Figure 33. The drawing above illustrates how rain gardens and rain barrels work together to capture runoff. The downspout isdirected into a rain barrel to collect roof runoff. In order to collect more roof runoff, two rain barrels are connected to each other.The excess runoff will pour out through the rain barrel’s over-flow valve. You can attach an overflow hose to the valve to helpdirect flow towards your rain garden. By storing the stormwater runoff in rain barrels, you’ll be able to water your rain gardenduring dry periods.
  33. 33. Maintenance BeforeGood design andregular maintenancewill continue to helpclean stormwater. AfterFigure 34. A Burnsville, MN home before and after rain garden construction. The City of Burnsville, MN constructedrain gardens to improve the water quality of Crystal Lake by adding rain gardens to a 20-year-old neighborhood. Tolearn more about the project visit your rain garden TLC to ensure it 30). Direct the overflow hose intofunctions properly. Tender loving care your garden so that excessive runoffdoes not mean 24-7 maintenance, but will flow from the hose into yourby making adjustments when needed, garden. Whatever is left inside theyou’ll be able to enjoy your garden rain barrel can be used to water yourthroughout the seasons (figure 34). In garden in times of prolonged drought.this section you’ll learn how to maintain Other rain barrel benefits include:your rain garden by measuring its  Lower water costs (a rain barrelperformance over time and can save approximately 1,300incorporating rain barrels into your gallons of water during peakrain garden design. summer months).  Beautifully designed rain barrelsRain barrels if built with the proper materials and tools (figure 35 onWater your plants immediately. They page 30).will need about an inch of water per  Naturally rechargesweek to become established. To help groundwater.regulate watering, incorporate rain  Reduced water pollution bybarrels into your rain garden design reducing stormwater runoff,(figure 33). Simply connect your rain which can contain pollutants likebarrel to the downspout draining to sediment, oil, grease, bacteria,your garden (figures 36 and 37 on page and nutrients. Maintenance 29
  34. 34. Maintaining your rain barrel is easy too. Keep these simple tips in mind for a properly functioning rain barrel.  Clear debris away from the inlet on a regular basis to allow roof runoff to pour into the rain barrel.  Unless your rain barrel can withstand freezing temperatures, clean out your rain barrel at the end of the season and store itFigure 35. Rain barrel artwork. indoors to prevent water from freezing inside of it. Freezing temperatures could damage your rain barrel. Performance evaluation Once you’ve constructed your rain garden you’ll need to maintain proper drainage and healthy plants. Consider the following tips to maintain your rain garden’s performance. Rain garden performance Visual inspections offer the easiest way to evaluate your garden for properFigure 36. Highland Beach Town Hall rain barrels. drainage. After a storm ends, visually inspect the rain garden for standing water at 24 and 48 hours. You’ll need about an inch of rain or more. If there is still standing water after 48 hours, you’ll need to make adjustments based on your site’s conditions (refer to pages 9 to 11). To verify proper construction and ensure long-term performance, check for the items below.  Sediment accumulation in the basin from the drainage area  Clogged inlet or outlet  Excessive erosion within theFigure 37. Connected rain barrels at Arlington Echo. garden30 Maintenance
  35. 35. Healthy native plants ESD Criteria # 20. MaintenanceYour native plants are the stars of the  Rain garden maintenance isgarden. Take care of them by applying generally no different than thatthe tips below to evaluate the health required of other landscapedof your plants. areas.  Begin with a record of the  The top few inches of the garden design showing the plants planting soil should be removed installed and their location and replaced when water ponds (refer to page 22). for more than 48 hours. Silts  Record the time of growing and sediment should be removed season and age of the garden. from the surface of the bed as  Describe the condition of the needed. site when you assess your plants.  Where practices are used to  With the help of a plant field treat areas with higher guide and your original garden concentrations of heavy metals design, identify the species (e.g., parking lots, roads), mulch present and their growth should be replaced annually. requirements. This will help Otherwise, the top two to three determine whether or not the inches should be replaced as correct species are present. necessary.  Record the color, size, and  Occasional pruning and quality of the leaves, stem, and replacement of dead vegetation flowers. Compare this to your is necessary. If specific plants original garden design. are not surviving, more  Estimate the percentage of appropriate species should be vegetative cover to determine if used. Watering may be required plants are established. during prolonged dry periods.  Inspect your garden for wetland  Rain gardens shall have a plant species to determine if maintenance plan and be hydric soils may be present, protected by an easement, deed indicating prolonged periods of restriction, ordinance, or other saturation. legal measures preventing its  Take pictures of your garden to neglect, adverse alteration and develop a complete record of removal. conditions at the time of your assessment. Your contribution  During a growing season, record Each rain garden you build cleans our observations as needed. Follow waterways so that one day we’ll say in these tips annually so that you’ll the watershed of the Chesapeake and have records to compare growing Coastal Bays, “What falls on site, stays seasons and note any changes. on site”. Maintenance 31
  36. 36. Rain Garden Checklist No. Task Page1. Locate your rain garden site. 5-62. Decide the best shape for your garden. 7, 19-203. Estimate its drainage area. 11-124. Figure out its surface ponding depth. 12-135. Determine your rain garden’s area. 13-146. Sketch out your garden’s dimensions. 15, 17, 237. Contact Miss Utility 1-800-257-7777. 178. Figure out your budget. 179. Make sure your garden catches the runoff 19 you’re planning to treat.10. Build a berm. 20-2111. Dig your rain garden. 2112. Consider adding rain garden soil mixture, 6-7, 20, mulch, or stones (optional). 21, 2713. Buy native plants. 24-25, 38-4314. Lay out and plant the rain garden design. 23-27, 37 Remember to cluster, cluster, and cluster!15. Incorporate a rain barrel into your garden 29-30 layout.16. Evaluate your rain garden for proper 30-31 drainage and healthy plants.17. Review environmental site design criteria ii, 1, 2-3, tips 1-20 to meet Maryland’s stormwater 5-6, 9, 12, managemet criteria. 17-18, 21, 23, 26, 3132 Rain Garden Checklist
  37. 37. Appendices Appendix A: Soil tests Appendix B: Rainfall depth by the Maryland Department of the Environment.Maryland Stormwater Design Manual,“Unified Stormwater Sizing Criteria” Appendix C: Rain garden templates by Low Impact Development Center Appendix D: Native plants by Maryland Cooperative Extension Swamp Sunflower Appendices 33
  38. 38. Soil testsFigure 38. Dig a hole first. Figure 39. Fill the hole with water. Figure 40. Lastly, track time.The percolation test and the clay test suitable for a rain gardencan help you identify soil type in your (figure 40).rain garden area.  If there’s water in the hole after 24 hours select another site or talk to a professionalPercolation Test landscaper.There are two percolation tests thatcan help you determine how fast water 2. Water in a candrains in your soil.  Remove the ends from a 46- ounce can or a large can of juice.1. Water in a hole  Insert the can two inches into  Dig a hole about 1-2 feet wide the ground. and 2 feet deep at the rain  Pour a quart of water into the garden site (figure 38). can.  Fill the hole with water  Depending on how many minutes (figure 39). it takes for the water to drain,  If the hole drains in less than you may or may not have suitable 24 hours, your soil is probably soils for a rain garden (table 4). Drainage Time Soil Porosity Drainage ConditionsLess than 4 Excellent percolations This soil offers the best drainage conditionsminutes and air circulation. for planting a rain garden.4 to 10 minutes Somewhat compact or Acceptable drainage for a rain garden but dense soil. slower; may need to aerate or augment soil.Over 10 minutes Overly compact or dense. Very poor drainage; challenging conditions. Must augment soil, mill, and aerate.Table 4. Drainage time.34 Appendix A
  39. 39. Clay-sandy soils testSoils with high clay content mayprevent proper drainage. Sandy soilsare the best soils for drainage. You canuse the tests below to identify soiltype or contact your local NaturalResources Conservation Serviceextension office for assistance.1. Clay ribbon  The simplest way to test for clay Figure 41. Dampen a handful of soil in your hands and or sandy soils (and at no cost) is knead the soil. Clay soil, when compacted, can prevent to dampen a handful of soil in drainage. Sandy soil feels gritty and may be more difficult to knead, crumbling in the palm of your hands. your hands (figure 41).  Knead the soil into a ball (figure 42).  Roll the ball between your hands to make a rope of soil uniformly thick (figure 43).  Allow the rope to extend unsupported over your forefinger until it breaks from its own weight.  If the rope extends unsupported greater than an inch before it Figure 42. Knead the soil into a ball about an inch in breaks, and feels more smooth diameter. than gritty, the soil may have too much clay in it. This site may be unsuitable for a rain garden. Select another site or talk to a professional landscaper.2. Soil maps  Soil maps are a good reference for a basic understanding of the soils in your neighborhood. They will tell you what soils are on and near the land.  Your local Natural Resources Figure 43. Roll the ball between your hands to make a rope of soil uniformly thick. If your rope breaks before Conservation Service extension extending an inch then you probably have sandy soils office will have soil maps for that allow proper drainage. This site may be suitable your area. for your rain garden. Appendix A 35
  40. 40. Rainfall Depth Chart Rainfall Depth (inches)County 1 yr - 24 hr 2 yr - 24 hr 10 yr - 24 hr 100 yr - 24 hrAllegany 2.4 2.9 4.5 6.2Anne Arundel 2.7 3.3 5.2 7.4Baltimore 2.6 3.2 5.1 7.1Calvert 2.8 3.4 5.3 7.6Caroline 2.8 3.4 5.3 7.6Carroll 2.5 3.1 5.0 7.1Cecil 2.7 3.3 5.1 7.3Charles 2.7 3.3 5.3 7.5Dorchester 2.8 3.4 5.4 7.8Frederick 2.5 3.1 5.0 7.0Garrett 2.4 2.8 4.3 5.9Harford 2.6 3.2 5.1 7.2Howard 2.6 3.2 5.1 7.2Kent 2.7 3.3 5.2 7.4Montgomery 2.6 3.2 5.1 7.2Prince George’s 2.7 3.3 5.3 7.4Queen Anne’s 2.7 3.3 5.3 7.5St. Mary’s 2.8 3.4 5.4 7.7Somerset 2.9 3.5 5.6 8.1Talbot 2.8 3.4 5.3 7.6Washington 2.5 3.0 4.8 6.7Wicomico 2.9 3.5 5.6 7.9Worcester 3.0 3.6 5.6 8.1Table 5. Listed in the table above are rainfall depths associated with the 1, 2, 10 and 100-year, 24-hour stormevents (source: Chapter 2 of the Maryland Stormwater Design Manual, “Unified Stormwater Sizing Criteria”, page2.11) . Maryland’s environmental site design (ESD) sizing criteria for new development requiring stormwatermanagement states that ESD practices shall treat the runoff from one inch of rainfall. However, if your water qualitygoal is to treat 100% of the runoff from a 1 year, 24-hour storm event, use the rainfall depth chart above todetermine how much rainfall you need to plan for. For instance, a Worcester County resident treating 100% ofrunoff from the 1 year, 24-hour storm event needs to size their rain garden to treat the runoff from a three inchstorm event. Refer to page 15 to learn more about sizing your rain garden based on targeting a rainfall amount.36 Appendix B
  41. 41. Rain garden templateNote: The number of plants for each designated area is approximate.Butterfly SwaleLow Maintenance, 250 SF, Coastal Plain, Full SunA - 10 Chelone glabra (White turtlehead)B - 13 Verbena hastate (Blue Vervain)C - 10 Amsonia tabernaemontana (Blue-star flower)D - 12 Lobelia cardinalis (Cardinal Flower)E - 13 Amsonia hubrechtii (Narrow-leaf Blue-Star flower)F - 12 Muhlenbergia capillaries (Pink Muhly Grass)G - 52 Carex stricta (Tussock sedge)H - 1 Magnolia virginiana (Sweetbay)I - 16 Aster novi-belgii, ‘Professor Anton Kippenburg’ (New York Aster)J - 7 Chelone lyonii (Pink Turtlehead)Butterfly Swale,Low Maintenance, 250 SF, Coastal Plain, Pt Shade/ShadeA - 10 Myosotis scorpioides (Forget-me-not) or Mertensia virginiana (Virginiabluebell)B - 13 Gentiana andrewsii (Bottle Gentian) or Aster cordifolius (Blue Wood Aster)C - 10 Amsonia tabernaemontana (Blue-star flower)D - 12 Lobelia siphilitica (Great Blue Lobelia)E - 13 Phlox divaricata (Woodland Phlox)F - 12 Aruncus dioicus (Goatsbeard)G - 32 Elymus hystrix (Bottlebrush Grass) or Ajuga reptans (Carpetbugle)H - 1 Aesculus parviflora (Bottlebrush buckeye)I - 16 Aster cordifolius (Blue Wood Aster) or Tradescantia virginiana(Spiderwort)J - 7 Viola papilionacea (Common Blue Violet) or Dicentra eximia (Hardy BleedingHeart) Appendix C 37
  42. 42. Native plants Whether you live in the coastal plain, piedmont, or mountain regions of the Chesapeake and Atlantic Coastal Bays Watersheds, the native plants you select will provide many benefits to your rain garden and the environment. Native plant benefits include:  Resilient to insects and disease, and are less likely to need pesticidesJacob’s Ladder  Best adapted to local conditions, e.g., no need to use chemical fertilizers  Conserving water , i.e., once plants are established in the right place, no need for supplemental watering  High habitat value provides food, shelter, and nesting areas for wildlife By growing native trees and shrubs you will also improve air quality and saveLyre-leaf Sage energy. Trees and shrubs can remove carbon dioxide (CO2) from the atmosphere during photosynthesis to form carbohydrates that are used in plant structure/function and return oxygen back to the atmosphere as a byproduct. About half of the greenhouse effect is caused by CO2. Trees also reduce the greenhouse effect by shading our homes and office buildings, lowering the cost of air conditioning during the summer. This section lists a few native ferns, grasses, sedges, flowers, shrubs, and trees adaptable to the coastal plain,Beebalm piedmont, or mountain regions.38 Appendix D
  43. 43. The key following will help you identify growing season, except inwhich native plants are suitable for droughts. These plants canyour rain garden based on sunlight handle saturated areas longer.exposure, its soil moisture content,  Average (A) areas are wherecolor, height, and bloom time. For the soil is damp, and may beadditional native plants, refer to occasionally saturated. PlantsNative Plants for Wildlife Habitat and can handle saturated and dryConservation Landscaping: Chesapeake soils.Bay Watershed.  Dry (D) areas are where water does not remain after a rain.Sunlight These areas may be in full sun or  Full sun (Su) receives direct in a windy location, on a steep sunlight for at least six hours a slope, or have sandy soil. Plants day during the growing season. in this category are drought  Partial shade (PS) receives tolerant. approximately three to six hours of direct sunlight during the growing season. Flower colors  Shade (Sh) receives less than The key below is a simplified list of three hours of direct sunlight or colors and includes all shades. filtered light.Soil Moisture Bl=blue O=orange R=red B=brown P=pink W=white  Moist (M) areas are where the G=green Pu=purple Y=yellow soil is saturated for much of theFerns Cinnamon Fern Royal Fern Sensitive Fern Common Name Scientific Name M A D Su PS Sh HeightCinnamon Fern Osmunda cinnamomea X X X X X 2-5’Maidenhair Fern Adiantum pedatum X X X 1-2’Northern Lady Fern Athyrium filix-femina X X X 1-3’Royal Fern Osmunda regalis X X X X X 1.5-6’Sensitive Fern Onoclea sensibilis X X X X X 1-3.5’ Appendix D 39
  44. 44. Grasses and sedgesBroomsedge Switchgrass Tussock Sedge Common Name Scientific Name M A D Su PS Sh HeightBroomsedge Andropogon virginicus X X X X 1-3’Switch Grass Panicum Virgatum X X X X X 3-6’Tussock Sedge Carex stricta X X X 1-3.5’HerbaceousWild Ginger Great Blue Lobelia Smooth Solomon’s Seal Common Scientific Name M A D Su PS Sh Height Color Bloom NameBeebalm Monarda didyma X X X X 2-5’ R, Pu Jul-AugBlueflag Iris Iris versicolor X X X X 3’ Bl, Pu May-JunGinger, Wild Asarum X X X X 0.5-1’ B, Pu Apr-May canadenseCardinal Flower Lobelia cardinalis X X X X 2-4’ R Jul-SeptCommon Eupatorium X X X X X 1-5’ W Jul-Septboneset perfoliatumFoamflower Tiarella X X X 0.5-1’ W Apr-Jul cordifoliaGoldenrod, Solidago rugosa X X X X 1-6.5’ Y Sept-Wrinkled-leaf OctGreat Blue Lobelia siphilitica X X X X 2-3’ Bl Aug-OctLobeliaJacob’s Ladder Polemonium X X X X 0.5-1.5’ Bl Apr-Aug reptans40 Appendix D