Plant Propagation for Home Gardeners


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Plant Propagation for Home Gardeners

  1. 1. Agriculture and Natural Resources FSA6024 Plant Propagation for Home GardenersJames A. Robbins Many home gardeners wish to sterile and typically holds too muchProfessor and reproduce special plants in their land­ water. Manufacturers often sell a soil­ scapes or start their own vegetable less media designed specifically forHorticulture Specialist ­ and bedding plants. Plant propagation propagation. The media should beOrnamentals is the controlled reproduction of moist before sowing the seed. For very plants using a variety of methods. small seeds, it may be easier to These methods can be broadly sprinkle the seeds on the media grouped into sexual and asexual surface and then use a fine spray of (vegetative) methods. Sexual propa­ water to settle them into the media. gation is focused primarily on For larger seeds, you can sow the propagating plants by seed. Seed seeds and then cover them with an propagation offers some advantages in appropriate depth of moistened media. that the technique is often economical The general rule of thumb for covering and efficient and lends itself to long- seeds is to cover the seed with two term storage. The primary disadvan­ times the diameter/width of the tage of seed propagation is that many seed. Again, use water to settle the seeds do not come “true to type,” so media in after topdressing the seed the offspring are not exact copies of with media. the parent. Asexual propagation tech­ niques include cuttings (e.g., root, stem, leaf), budding or grafting, layer­ ing and division. Asexual propagation techniques, while often more labor intensive than seed propagation, do allow the gardener to get an exact copy of the parent plant. Seed Propagation Seed propagation is commonly used by a home gardener when starting plants for the vegetable Figure 1. Germinating seed. garden or for some bedding plants. Most gardeners are well aware of how to prepare a seedbed in a vegetable Keeping the media moist (i.e., not garden and then follow the directions wet and not dry) during germination on the seed packet to sow the seeds. of the seed is critical. Once the media is at the correct moisture level, simple Starting seeds indoors for the techniques can be used to maintain vegetable garden or for bedding plants that level for the entire germination is fairly simple. The two most critical period. One simple method involves factors are using a high-quality seed placing a glass plate or sheet of plas­Arkansas Is germination mix and then keeping the tic or Saran™ above the lip of the seeds moist but not overly wet. Media seed tray or container. If the plate orOur Campus for seed germination should ideally be sheet is elevated just slightly above sterile, most likely consist of a the media surface, it will need to be significant percentage of peat moss raised or removed once the seedsVisit our web site at: and never contain garden soil. Garden begin to germinate and grow. The soil is a poor choice because it is not other common option is to place a University of Arkansas, United States Department of Agriculture, and County Governments Cooperating
  2. 2. clear plastic bag over the container, again with the surface. Seeds can also be scarified using hot watergoal of simply trapping existing moisture contained in (170 to 212 degrees F). With this method, simply dropthe media. If the bag is not rigid, it is common to use the seeds into four to five times their volume of hotan appropriate length of bamboo stake or chopstick to water, remove water from the heat source and let thekeep the bag from collapsing in on the fragile seeds soak for 12 to 24 hours unless the literatureseedlings. Some seedlings are very sensitive to salts states water; therefore, for small seed germinationprojects, you may wish to use deionized bottled wateruntil seedlings are up and actively growing. If seed Vegetative Propagationhas been sown with a high density, you will mostlikely have to transplant the fragile seedlings to a Vegetative (asexual) propagation techniquesdifferent container (e.g., cell pack) to allow the include cuttings (e.g., root, stem, leaf), budding orseedlings to reach a size that can be transplanted into grafting, layering and division. Propagation tech­the garden or landscape. niques such as cuttings, layering and division can be easily performed by home gardeners; however, budding and grafting typically require more skill. Cuttings An understanding of terminology is required before going further. A number of terms are used when discussing cutting propagation. Simple terms are used to describe where the cutting originatedFigure 2. Seed germination trays. from (e.g., root, stem, Figure 3. Typical three-node leaf), or with stem semi-hardwood cutting with Especially with woody plants, you will need to cuttings, the relative basal leaves removed.become familiar with two terms: stratification and age of the wood/tissuescarification. In a simple sense, stratification involves (e.g., softwood, semi-hardwood, hardwood). With stemdifferent methods imposed by man to cause seeds to cuttings, we may also refer to the number of nodes.germinate after simulating environmental conditions Nodes are simply the locations on the stem where thethat seeds would normally experience in nature. For leaves originate from (i.e., more precisely, where theexample, think about a red oak acorn that falls to the buds are located). It is also common to refer to theground in the fall. In nature it is exposed to winter overall position on the stem that the cutting wastemperatures and then begins germinating the taken from (e.g., terminal, sub-terminal). For exam­following spring. The internal signals keep the acorn ple, it is common for a gardening book to instruct youfrom germinating in the fall before harsh weather to collect “terminal cuttings with three to four nodes.”sets in. Knowing this, if you harvest red oak acorns in With most cuttings, you also need to pay attention tothe fall and then want to germinate the seed indoors, the original “up and down” ends of your cuttingsyou need to replicate what would have gone on in (polarity). If you think you will have trouble keepingnature. Therefore, the red oak acorns are placed in a track once you have removed a cutting from a stem,container with moistened media and then placed in a you can simply use a lateral or cross-cut to referencerefrigerator (32 to 45 degrees F) for three months. the top/“up” and an angle cut to reference theThese “stratified” seeds can then be removed from the bottom/“down” of the cutting.refrigerator and sown, and germination should beginsoon if the temperatures are suitable. Reference The media you use to root cuttings can have abooks will clearly mention what kind of stratification significant impact on your rooting results, not onlyregime is required for each species. the number of new roots but the growth of these roots. An ideal rooting media needs to be sterile, well Scarification is any physical process that softens drained and provide adequate oxygen. Individualor damages the seed coat making it more permeable components that are most commonly used includeto water and air. Again, propagation books clearly coarse perlite, coarse vermiculite, peat moss andindicate which species require scarification to sand/pumice. These individual components can beimprove germination. Plants in the Legume family combined in a variety of ways and percentages.are one group often mentioned. For small seeds, you Examples include 50% peat moss: 50% perlitecan simply place the seeds between two layers of (volume basis); 50% perlite: 50% vermiculite; 100%medium sand paper and then rub the sheets back and perlite; 100% sand/pumice; and 100% peat moss.forth. For larger seeds (e.g., Kentucky coffee tree), Rooting cubes (e.g., Oasis Rootcubes®) made out ofyou can use a metal or nail file to abrade the seed foam are also used.
  3. 3. have formed roots, you can start this transition by periodically venting your cover with increasing frequency to reduce the relative humidity slowly over time.Figure 4. Effect of media on rooting performance.Left: vermiculite, peat moss, perlite, peat:perlite The rooting environment has a major influenceon the rooting results. Remember that with cuttingswe have separated a portion of the plant from theparent plant, thus removing its source of water andnutrients until a new root system has reestablished. Figure 5. Simple propagation option using plastic bag.Environmental conditions that add stress or hastenwater loss diminish the rooting success. Therefore,conditions such as high light, high temperature orbreezy conditions often have a negative impact on therooting results. Even with cuttings that have leaves,it is hard for people to imagine that making “food” isnot a priority, but forming roots is. Cuttings will relyon stored “food” until new roots are regenerated. Withthis in mind, ideal temperature conditions for mostcuttings are to have the air temperature 10 to 15degrees cooler than the rooting media. Ideal tempera­tures for many types of cuttings would be an ambienttemperature of 55 to 65 and a media temperature of65 to 75 degrees F. In most home situations, having adual temperature is difficult; however, garden Figure 6. High dome for rooting cuttings.suppliers do sell waterproof heating mats designedspecifically to place propagation trays on to elevatethe media temperature. As for light levels, it is criti­cal to keep cuttings out of direct sunlight until theyhave rooted. Appropriate light levels can be found innorth-facing windows or by using grow lights in darkrooms or basements. The critical factor with cuttings that containleaves is to maintain the highest level of relativehumidity possible around leaves until roots form.Commercial propagators use intermittent mist sys­tems or fog systems to achieve this goal. While these Figure 7. Simple propagation tray.options are possible for a homeowner, there are easiersolutions. No matter what option you chose, the goalis the same: you are trying to trap moisture alreadypresent in your rooting media. For very few cuttings,using an inverted Ziploc™ bag or one-half of a clearplastic soda bottle works very well over a single pot.If you use the threaded end of a plastic bottle, youcan easily remove the bottle cap to vent moisture if itbuilds up too high in the bottle. For large numbers ofcuttings, it is easier to use a seed tray or flat. To trapmoisture when using a tray, use a clear tray lid orpieces of bent strap metal (Fig. 7) to keep a plasticbag from touching the cuttings. With most leafycuttings, we need to transition or “harden off” cut­tings before planting them outside. Once cuttings Figure 8. Plastic bottles (top or bottom) for rooting cuttings.
  4. 4. Houseplants (lamina) and the petiole that attaches it to the original stem. This method is commonly used for Many different kinds of common houseplants can African violet, peperomia and some begonias. Rootsbe easily propagated by stem, cane or leaf cuttings and a new plantlet typically originate at the base ofand by division or layering. the petiole.Stem Cuttings Leaf-Blade Cuttings – Leaf-blade cuttings consist of the leaf blade only and are commonly used to There are a number of common houseplants that propagate many succulent plants such as jade plantcan be easily propagated by stem cuttings. These and sedums. In this case the leaf is most commonlyinclude coleus, begonia, Christmas cactus, fuchsia, inserted vertically into the media with a majority ofgeranium, poinsettia, rubber plant, shrimp plant and the leaf visible above the media surface. Roots andwandering jew. Take cuttings from shoots that are new plantlets typically originate from the base of thevigorous, pest free and, ideally, not flowering. leaf. One exception would be kalanchoe. In this caseCuttings will typically be 4 to 6 inches long depend­ you lay the leaf horizontally on the media surfaceing on the plant. Cut the stem just below a node with and plantlets will develop at many of the serrationsa sharp knife or razor blade. Remove leaves from the or notches in the margin of the leaf.lower half of the cutting and dip the basal 1 to 1.5inches in a rooting hormone. Rooting hormone is Leaf-Vein Cuttings – The classic example of thisprobably not necessary for easy-to-root plants such as cutting method is the begonia. You simply lay the leafcoleus and fuchsia, but it will not hinder the rooting on the media surface and cut several slices perpen­process either. Carefully stick the dipped end of the dicular to the major leaf veins. Some people also flipstem cutting into the rooting media. Some people like the leaf over and lightly dust those cuts before layingto pre-drill the hole using the eraser end of a pencil. the leaf back on the media surface. Roots andThe rooting media would then be firmed around the plantlets will develop at the cuts in the veins.cutting after inserting into this preformed hole. Leaf-Section Cuttings – The most common A modification of this works well for foliage example of this technique is used to propagateplants that have a larger stem such as dumb cane, mother-in-law’s tongue (Sansevieria). In this case youcorn plant and Chinese evergreen. In this case you cut the long “tongue-like” leaf into 2-inch segmentswill remove a leafless section of the stem, now and insert the bottom ½ inch into the rooting media.referred to as a cane, and lay this cane horizontally Remember to keep the original orientation of theon the media surface. If the cane is thick, you will leaf intact (polarity). Some of the baby plantlets thatpush the cane slightly into the media surface so you will form at the bottom of the leaf piece from aget good media contact. variegated selection may develop as green only (i.e., no variegation).Leaf Cuttings Leaf cuttings are used to propagate many house­plants including begonia, African violet, Episcia, glox­inia, jade plant, kalanchoe, mother-in-law’s tongueand peperomia. There are several variations of leafcutting types depending on what parts of the leaf areused and whether a leaf petiole is attached or not. Leaf-Petiole Cuttings – Just as it sounds, a leaf-petiole cutting includes both the wide part of the leaf Figure 10. Mother-in-law’s tongue leaf-section cuttings. Preformed Plantlets – A small number of house­ plants produce preformed plantlets along aerial shoots. Examples include spider plant, wax plant (Hoya) and strawberry begonia (Saxifraga stolonifera). Propagation is simple involving the removal of these plantlets (with or without aerial rootlets) and then inserting the base of the plantlets in a high-quality potting soil and treating theFigure 9. African violet leaf-petiole cuttings. plantlet as if it were a stem cutting.
  5. 5. Outdoor Plants Many of your favorite outdoor shrubs, vines andground covers can be easily propagated by cuttings.Softwood Cuttings Softwood cuttings are prepared from the soft,succulent, new flush of growth. Many ornamentalplants can be propagated by softwood cuttings includ­ing lilacs, forsythia, magnolia, weigela, oleander,pyracantha, spirea, apple, peach, pear and plum.While softwood cuttings tend to root easily and faster,they may require more care since the soft tissue ismore susceptible to drying. In general, with softwood Figure 12. Hardwood cutting.cuttings, we are talking about cuttings that aretypically 3 to 4 inches long, with two to three nodesand the basal leaves removed before inserting the Root Cuttingscutting into the media. Root cuttings are used very rarely and only on a few species that typically do not root well from stemSemi-Hardwood Cuttings cuttings. These include Aesculus, Aralia, Realistically, terms such as softwood and semi- Koelreuteria, sumac (Rhus) and sassafras. The mosthardwood are not absolutes. Once the very soft flush challenging aspect of root cuttings is uncovering fromof new growth starts to stiffen up and form “wood,” soil the roots of your desired plant and not somewe have likely passed into the semi-hardwood stage. other plant. While root cuttings may be made at anyA majority of our common ornamental shrubs are time of the year, it is probably more common to dopropagated from semi-hardwood cuttings. Plants such this in the dormant season. Root pieces can be held inas viburnum, camellia, azalea, holly, crape myrtle, moist media in a cooler (>38 degrees), placed nearlyhydrangea and euonymus use this type of cutting. horizontal in rooting media like you would treat otherIn Arkansas this peak time is often between May 15 cuttings or direct planted in well-prepared gardenand June 15. soil with the top of the root-piece just barely emerging from the soil. Grafting/Budding Realistically, grafting or budding is not an easy technique for home gardeners to master. Most people would be amazed at how many ornamental plants in their landscape originated from budded or grafted plants. Many shade trees, all Japanese maples, many weeping plants and all hybrid tea roses use these techniques. Budding or grafting is also the mainstay of the tree fruit industry. Budding and grafting are essentially the same technique; however, with budding you are simply attaching the bud from your desired plant to the rootstock/understock, and withFigure 11. Dipping prepared holly cutting in rooting grafting you are using a piece of stem that containshormone. many buds on it. The obvious advantage of bud­ ding is you can potentially get many more plantsHardwood Cuttings from your desired scion/stockplant. The major Hardwood cuttings are made from woody,dormant wood on deciduous plants (e.g., grape,poplar, rose, willow, peach, wisteria, elderberry,blackberry, forsythia) or some needle evergreens (e.g.,junipers, arborvitae). Hardwood cuttings are easy toprepare and less perishable. For deciduous plants thecuttings are leafless and tend to be longer than soft­wood cuttings. Hardwood cuttings are typically 6 to12 inches long. As a general rule for the needle ever­greens, rooting percentages tend to be increasedwhen cuttings are harvested in mid- to late winter.As a general rule, higher rooting percentages occuron junipers when a small “heal” of wood is includedat the base of the cutting. Figure 13. Chip budding.
  6. 6. disadvantage of budding is that you are typically for plants such as wisteria, brambles, forsythia,working with a very small bud versus a larger piece weigela and spirea. Ground layering simply involvesof stem that is easier to handle. A good propagation bending an intact shoot over and burying the middletext can go into the specific details related to budding portion (i.e., shoot tip comes back up above groundand grafting. and is exposed) under the existing soil. You may wish to wound the lower portion of the bent stem. WithLayering easy-to-root plants, roots will often form along the Layering is a method of rooting a new plant while buried stem. Once roots have formed, you simply cutthe stem is still attached to the parent plant. It is the stem below the rooted zone, excising the plantsimple to perform and can be done in the home from the mother plant.without special equipment orstructures. Division Air Layering – In the Many home gardeners did not realize that theycase of air layering, we are were actually plant propagators when they dividedforming roots on stems well common perennials such as cannas, hosta, daylilies,above the soil. This method iris, peonies, bleeding heart, many ornamentalcan be used successfully on a grasses, ferns and lily-of-the-valley. As a general rule,number of common tropical the best time to divide plants is during the dormanthouseplants including croton, season.dumb cane (Dieffenbachia),dracaena, rubber plant andschefflera. Resources The process is quite Bubel, Nancy. 1988. The New Seed Starter’ssimple. First, pick a point in Handbook. ISBN-10:0878577521. Figure 14. Air layeringthe stem at least 10 to 12 Mahonia. Dirr, M.A., and C.W. Heuser, J. 2006. The Referenceinches from the tip. Remove Manual of Woody Plant Propagation: From Seedall leaves several inches on either side of the region to Tissue Culture: A Practical Working Guide towhere you will make your air layer. The area will the Propagation of Over 1,100 Species. Varsitytypically be about 6 inches in length. Two types of Press. ISBN-10:0942375092. Basically an A to Zstem cuts are typically used. One involves making an recipe book for propagating woody ornamentalupward-angled cut into the stem that stops about plants.halfway through the stem. The other method involves Druse, Ken. 2000. Making More Plants: The Science,removing a ring of the outer bark. The ring of bark Art and Joy of Propagation. $32. ISBN-10:tissue will be 1 to 1.5 inches long. Apply a rooting 051770787X.hormone to the cut surfaces. If an angled or vertical Gowdy, Mary Ann. 2002. Home Propagation of House­cut has been made into the stem, you will want to plants. University of Missouri - Columbia. G6560.prevent that from closing by inserting a small piece toothpick in the wounded area. Next, take a hand­ agguides/hort/g06560.pdf.ful of moist sphagnum moss and pack the moss in Hartmann, H.T., D.E. Kester, F.T. Davies, Jr., andand around the cut surfaces. To retain the moisture R.L. Geneve. 2001. Plant Propagation Principlesaround the wounded area for weeks/months, wrap a and Practices. Prentice-Hall. 7th edition. ISBN­layer of plastic sheet around the entire work area 10:0136792359. This is considered the bible ofand seal both ends with electrical tape. Many people plant propagation. It is used in every college andalso cover the plastic with aluminum foil to prevent university. Expensive, but thorough.any light from penetrating the rooting zone and to Heffernan, Maureen. 1997. Burpee Seed Starter. Johnreflect any heat from sunlight. You can simply keep Wiley & Sons. ISBN-10:0028610024.your foliage plant in the same place (i.e., indoors oroutdoors) where it was originally growing. Once rootsdo form, simply make a single cross-cut in the stem Suppliesbelow the rooting zone. You should end up with roots • Your local garden supply store can often provideon the bottom and leaves at the top: a new plant. trays, media and rooting hormone. Ground Layering – Ground layering can be • A.M. Leonard, Piqua, OH, to easily propagate a number of ornamental • Hummert International, Earth City, MO,shrubs and vines. This simple technique works well No endorsement is implied or discrimination intended for firms or references included or excluded from this publication. Printed by University of Arkansas Cooperative Extension Service Printing Services.DR. JAMES A. ROBBINS is professor and horticulture specialist - Issued in furtherance of Cooperative Extension work, Acts of May 8ornamentals, University of Arkansas Division of Agriculture, and June 30, 1914, in cooperation with the U.S. Department ofCooperative Extension Service, Little Rock. Agriculture, Director, Cooperative Extension Service, University of Arkansas. The Arkansas Cooperative Extension Service offers its programs to all eligible persons regardless of race, color, national origin, religion, gender, age, disability, marital or veteran status, or any other legally protected status, and is an Affirmative FSA6024-PD-4-08RV Action/Equal Opportunity Employer.