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Garden Weeds - notes


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  • 1. 1/7/2013Out of the Wilds and Into Your Garden Weeds & More Weeds C.M. Vadheim and T. Drake CSUDH & Madrona Marsh Preserve Madrona Marsh Preserve Gardening with Western L.A. County Native Plants September 5th 2009 Project SOUND - 2009 © Project SOUND © Project SOUND Does this look like your garden? What is a weed? (definition)  Weed: any plant that is growing at a site where it is not wanted You’re not alone – weeds are a perennial concern in S. California gardens! © Project SOUND © Project SOUND 1
  • 2. 1/7/2013 Why control weeds? (it’s a war out there!) Weeds are particularly challenging in W. L.A. County  Weeds compete with desirable  No killing frosts or smothering plants for: snow; weeds that are annuals in  Light many climates are perennial in  Water ours  Nutrients  No killing high temperatures  Space  Weeds also provide hiding  People water a lot (up to now) places for insects and serve as a  Lots of weedy plants to spread source of plant diseases. their seeds/invade via roots  Weeds can kill a gardener’s  Use of ‘mow & blow’ gardeners – enthusiasm, which can cause weeds hitch-hike between them to abandon the garden; Castor Bean ( Ricinus communis) gardens Game ends – weeds win projectprofiles/art26290.html © Project SOUND © Project SOUND Where do alien weeds come from? Weeds tell a story….  Many of California’s noxious and invasive weeds came from regions with comparable  Type of soil – some prefer climates in the Mediterranean certain soil characteristics region, Australia, S. Africa  Available light  Others, including many garden  Soil nutrient levels (low or Mediterranean Climate Zones weeds come from nearly all high) parts of the globe, including particularly western and  Watering practices central Asia, Russia & Europe  Cultivation practices – how  They were introduced through much the soil is disturbed human activity, both To know a weed is to accidentally and intentionally, learn about your garden –  And many other things including by gardeners. and to understand how to Percentage of invasive plants accidentally or combat it! intentionally introduced to California. © Project SOUND © Project SOUND 2
  • 3. 1/7/2013 In the garden (and in the operating room), first do no harmThe more you know about your garden’s own weeds, the better you Your plan to combat weeds should be reasonable andwill be able to deal with them environmentally friendly © Project SOUND © Project SOUND The IPM Pyramid – ‘first do no harm’ Integrated Pest Management (IPM)  Use the least invasive – and often most effective - means first: "Optimum combination of control methods  Prevention – cultural practices including biological, cultural, mechanical,  Mechanical Controls  Naturally occurring physical and/or chemical controls to reduce biological controls (native) pest populations to an economical  Consider using non-native acceptable level with as few harmful biological controls (herbivores; diseases) effects as possible on the environment and  Use chemical controls nontarget organisms." sparingly, as a last resort: Non-native and chemical controls may  Naturally occurring elements R.L. Hix,CA Agric. Magazine, 55:4 (2001) have the important drawback of non-  Biologics – chemicals made specificity – they kill the good species by plants that are toxic to weeds along with the bad.  Non-biologic herbicides © Project SOUND © Project SOUND 3
  • 4. 1/7/2013 An IPM system is designed around six basic components An IPM system is designed around six basic components 1. Set Action Thresholds  Before taking any pest control action, IPM first sets an action threshold, a point at which pest populations or environmental 4. Mechanical controls: Should a pest reach an unacceptable level, conditions indicate that pest control action must be taken. The level mechanical methods are the first options to consider. They at which pests will either become an economic threat is critical to include simple hand-weeding, erecting weed barriers, and tillage guide future pest control decisions. to disrupt breeding. 2. Monitor and Identify Pests 5. Biological controls: Natural biological processes and materials can  Not all insects, weeds, and other living organisms require control. provide control, with minimal environmental impact, and often at IPM programs work to monitor for pests and identify them low cost. The main focus here is on promoting beneficial accurately, so that appropriate control decisions can be made in herbivores that eat target pests. Use of plant pathogens – ones conjunction with action thresholds. This monitoring and specific to the weeds of interest - also fits in this category. identification removes the possibility that pesticides will be used when they are not really needed or that the wrong kind of pesticide will be used. 6. Chemical controls: Synthetic pesticides are generally only used as required and often only at specific times in a pests life cycle. 3. Preventive Cultural Practices Many of the newer pesticide groups are derived from plants or  As a first line of pest control, IPM programs work to manage the naturally occurring substances (e.g.: allelopathic analogues), and crop, lawn, or indoor space to prevent pests from becoming a further biology-based or ecological techniques are under threat. These control methods can be very effective and cost- evaluation (particularly for agriculture, forestry applications). efficient and present little to no risk to people or the environment. © Project SOUND © Project SOUND Integrated Pest Management (IPM) If you can, do a little bit – but do it consistently applies to weeds as well as other pests  Set Action Thresholds  Does your entire yard need to be weed free? Choose an area and focus on it.  Prioritize weeds by invasiveness  When to take action against specific weeds  In general, a smaller weed is easier to remove than a larger one  In general, you want to remove a weed before it flowers & sets seed Weeding just 15-30 minutes a day is often all that’s needed © Project SOUND © Project SOUND 4
  • 5. 1/7/2013 Integrated Pest Management (IPM) Climate change: long periods of hot Monitor and Identify Weeds weather during winter rains  Get to know the ‘weed seasons’ of your yard:  Cool-season weeds sprout any time from fall through spring. They flower in late spring/early summer. The plant may disappear during the hot dry summer, but you’ll see even more of germinating seedlings the following fall. Cool season weed  Examples: Annual Bluegrass, BermudaAnnual Bluegrass – Poa annua Buttercup; Mustards; Clovers; Cheeseweed  Warm-season weeds tend to start growing in the spring and hang around all through the growing season.  Examples: Crabgrass; Bermuda Grass; Kikuyu Grass; Fountain Grass; Spotted Spurge; Bindweed; Nutsedge;  Any season – some species grow all year long in our climate Favors growth of many weeds: jump-start on growth season Warm season weed  Examples: Creeping Woodsorrel (Oxalis) ; Crabgrass – Digitaria species Example: Panic Veldt Grass - Ehrharta erecta © Project SOUND © Project SOUND Integrated Pest Management (IPM) Each garden is unique: garden weeds in context Monitor and Identify Weeds  Soil (including previous amendments)  Get to know the geography of  Light & water your garden’s weeds  Gardening practices: tilling, raking, mulches, ‘top soil’, hired gardener’s  Areas prone to weeds require practices special monitoring & early intervention  The age of the garden (or part of the garden)  Discovering geographic patterns  Previous (and current) plants may suggest changes in gardening  Weeds that hitch-hike in with purchased practices – decreasing water to the plants area; increased hand-weeding  Invasive garden plants [ivy; bamboo; frequency; etc. dichondra; etc]  Know that wildlife (birds, etc) will Dichondra  What’s growing nearby: bring seed into your yard. Be extra Dichondra micrantha  Birds bring seeds; seeds blow vigilant in areas where they eat, (Dichondra repens)  Weeds grow into the yard Oxalis/ Creeping Woodsorrel perch etc. Oxalis corniculata We will introduce you to some general principles, strategies and tools © Project SOUND that you can apply to your own situation © Project SOUND 5
  • 6. 1/7/2013Garden weeds may vary widely from year to year… The Weed IPM plan for your garden – a work in progress  Example: Shepherd’s Purse (Capsella bursa-pastoris)  Requires observation &  Why? knowledge – specific for  Conditions are right for your garden germination of dormant seeds; temperature; rainfall  Will vary somewhat with:  Seeds survive up to 35 years in  Yearly weather conditions undisturbed soils  Maturity of plants  When conditions are right – they are ready  New plants, and other changes to the garden  New seeds may have been brought in by gardening practices  Will be modified based on  New seeds may have come in your previous experiences through natural means; wind, birds, etc.  Suggestion: keep a garden notebook/journal © Project SOUND © Project SOUND Identifying weeds Great resources on-line & in books  Proper weed identification may be your hardest task.  Flowering and growing patterns are of great importance as most weeds are classified as either annual, biennial, or perennial.  The color, shape, and placement of the flower on the weed will also aid you in identifying the weed.  Take pictures of the weeds – or collect and Kikuyu grass press them - as you find them; makes Pennisetum clandestinum identifying and recognizing weeds much easier.  Try to find them on-line, in books or have them identified by an expert (County agriculture extension; local weed control district).  If “new” or unfamiliar weeds appear, have them identified quickly and take appropriate control measures if necessary © Project SOUND © Project SOUND 6
  • 7. 1/7/2013 Identifying weeds is key to your weed strategy Integrated Pest Management (IPM) Preventive Cultural Practices  Knowing the ID of a weed will tell you:  The first line of defense against all weeds is  Growth pattern – annual or good prevention perennial weed  General goals:  Cool/warm season weed – when to look for it  Prevent the introduction of weeds into the garden  How it likely enters your garden  Prevent the spread of weeds in the garden – suggests ways to prevent this  Promote the health & vigor of desired species  Useful mechanical/physical  ‘An once of prevention is worth a pound of cure’ controls – simple preventive practices can save you  Chemical controls (if needed) serious gardening headaches Kikuyu grass is used for lawns © Project SOUND © Project SOUND Common Purslane - Portulaca oleracea Prevention/Cultural Practices – avoidance/  Characteristics: prevention is key  Succulent foliage (healthy edible;  Avoid introducing new probably should be grown as a garden weeds into the garden: vegetable)  Grows in moist areas (usually)  Use only weed-free mulch,  Summer (warm season); origin - Asia topsoil, other amendments (if any); beware of ‘free’ material  Growth form: herbaceous annual unless you know it will not contain weeds/weed seeds  How it spreads: seeds (> 50,000 per plant; stem pieces  Check new plants to be sure that weeds are not  Control Methods: ‘hitchhiking’ in the pots  Solarization for pre-planting removal.  Be sure to not bring weed  Mulch & dry conditions usually prevent it seeds into garden on your from establishing clothes, shoes, etc.  Easy to pull or hoe, but pieces of stem can re-root readily, so be sure to remove them from the garden. © Project SOUND © Project SOUND 7
  • 8. 1/7/2013 Cultural practices: just good old garden Cultural practices: good garden management management practices  Keep garden plants healthy; help them to out-compete the weeds  Sanitation  Plant native plants densely  Clean equipment (including lawnmowers) to prevent spread of enough to crowd out weeds weed seeds/cuttings  Choose native plants that:  Weed Disposal:  Are vigorous growers – will out-  Annual weeds can be composted if compete the weeds they are not in seed.  Will prevent weeds from growing  Place perennial weeds in a garbage by: bag, solarize (leave bag in sun) & clueless.html dispose of them in green waste.  Providing too much shade Note: a ‘hot’ compost bin will kill  Producing allelopathic chemicals that some – but not all – weed seeds,  If any weed is a big problem in your either inhibit weed seed germination garden, think twice before putting it so be cautious or weed growth: examples: Salvias?, in the compost pile. Chamise, Manzanitas, CA Walnut, Purple Sage – Salvia leucophylla probably other CSS species © Project SOUND © Project SOUND Integrated Pest Management (IPM) Fortunately, weeds need water to germinate Physical Prevention – 2nd line of prevention and grow  Weeds have growth requirements -  Water-wise gardening methods like any other plant: will limit some weeds, simply by  Water decreasing available water  Particularly helpful for shallow-  Correct amount of light rooted weeds  Correct temperature  Also useful for ‘weeds of wet places’ – will not survive in dry  Appropriate nutrients soil  Prevent seed germination & seedling  Use target watering methods – growth by limiting the weed’s access water only the plants you want to ‘growth requirements’ (drip; hose)  Remember: limit any one of these  Be patient – first couple of and you’ll significantly decrease the years, when you need to water ability of a weed to take over your shrubs more, are the worst garden Broadleaf Plantain - Plantago majorBlack Nightshade - Solanum nigrum © Project SOUND © Project SOUND 8
  • 9. 1/7/2013 Broadleaf Plantain – Plantago major Before planting a new area…prevention  Characteristics: almost always better than control  Large leaves from basal rosette; originally brought from Europe as medicinal plant  Kill weed plants & seeds  Usually in damp area of garden  Solarization  Chemical methods  Growth form: herbaceous perennial  How it spreads: seed  Turn the soil as little as possible – avoid bringing up  Control Methods: buried weed seeds  Crowd out; needs bare soil to germinate, grow  Decrease water; aerating the lawn will also  Control weeds before help. installation – always less work  Dig out before they set seed. Be sure to in the long runhttp://www.wildflowers-and- remove as much of the roots as possible -  Be patient – the more regrow from any pieces of the fibrous weeds/seeds are removedYou can use your knowledge of rootstalk that remain in the soil. before installation, the fewera weed’s growth requirementsto save time and effort  Chemical control -spot-treat with glyphosate you’ll have to pull later (Roundup), taking care not to get the chemical Bermuda Grass on desirable plants. Cynodon dactylon © Project SOUND © Project SOUND Understanding seeds: what seeds need to Key preventive method: blocking sunlight germinate so light-requiring seeds can’t germinate  Water – need to ‘re-hydrate’ before seedling can start to grow  Mulches  Light (small seeds, including many weeds) or dark (larger seeds)  Organic  Inorganic Virgin’s Bower - Clematis ligusticifolia  Correct temperature; may be warm Native plant – requires cold treatment or cool – and may be a rather narrow  ‘Weed block’ methods range. In general, weeds tend to have larger ranges, but many are  Planting natives that will ‘warm season’ or ‘cool season’ weeds create shade  Other factors (heat; smoke; cold pre-treatment, etc): in general, Oxalis/ Creeping Woodsorrel weed seeds have few of these – it’s Oxalis corniculata one of the reasons they are so Weed – no special requirements successful © Project SOUND © Project SOUND 9
  • 10. 1/7/2013 Why barrier methods work: Plastic weed barrier cloth (weed block) – several effects is it good for native plant gardens?  Block light, preventing seed Arguments for Arguments against germination  Doesn’t stop all weeds from growing  Physically prevent seedling  Stop some weeds seeds  Weeds grow through the holes cut for growth from germinating; blocks planting  Reduce soil temperature – light & forms physical  Weeds grow through/on top of the particularly in spring – delay barrier barrier cloth emergence  Relatively easy to install  Cloth gets clogged over time – becomes a water barrier  Increase soil moisture below the barrier – too much for  Can promote stem & root fungal disease some species (seeds & in trees & shrubs; interferes with seedlings rot) proper drainage  Decrease moisture above the  Doesn’t allow groundcover plants to barrier – too dry for root – or for successful re-seeding germination  Hard to keep from looking unsightly-  Chemical compounds released even under mulch from barriers/ mulch may inhibit germination and/or kill  Can’t be used well on slopes or other seedlings uneven terrain © Project SOUND © Project SOUND Physical barriers Eco-friendly ‘weed have their place block’ choices  Weedblock (plastic or other)  Newspaper (use a good  Under pathways  Under patios, sitting areas thickness to block light) (hardscaped areas)  Cardboard  Other areas where planting is not an option  Degradable weed block  Other physical barriers (e.g., mowing strip, heavy metal or materials – most are wood strip set on edge) at shrub paper-based bed/turf interface to prevent turf and turf weeds from encroaching into planted beds You may also choose more eco-friendly barriers © Project SOUND ‘Garden Trail’ weed block © Project SOUND 10
  • 11. 1/7/2013 What kinds of seeds Mulch – the best surface physical barrier are susceptible to for native plant gardens ‘dark inhibition’?  Kind of mulch  annual species that are small-  Should be appropriate for the native seeded and have a light plants you’ve planted requirement for germination  Organic (bark, etc) for most local such as common lambsquarters shrubs/trees ‘Garden Trail’ weed block and pigweeds are sensitive to  Inorganic for Coastal Prairie surface barriers (wildflowers) and desert plants  large-seeded annuals and  Must be course enough texture to perennial weeds are relatively allow the mulch surface to dry out insensitive to the darkness; however barriers/mulches still  Depth of mulch layer provide mechanical barriers to seedling growth.  Must be deep enough to prevent Lesson: geography of weeds light from reaching the seeds suggests that mulch layer may be beneath it. too thin at the edge © Project SOUND © Project SOUND IPM plan changes through the life of a garden/bed Knowing the life cycle of weeds is key to your plan  Knowing the ID of a weed will tell you:  Growth pattern/life cycle – annual, biennial or perennial weed  Cool/warm season weed – when to look for itPre-planting: Prevention/removal Annual weed – Gnaphaleum sp.  How it likely enters your garden – suggests ways to prevent this  How it spreads  Useful mechanical/physical controls  Chemical controls (if needed) Years 1-2: Monitoring & Removal Perennial weed - Oxalis pes-caprae © Project SOUND © Project SOUNDPre-planting: Prevention/practices 11
  • 12. 1/7/2013 Annual, Biennial & Perennial Weeds Annual weeds  Spread by seed. They may self-seed or they may be brought into the garden by wind, water, birds, animals or people. Short-lived (fixed) Spreading  The most important way combat annual Character Annuals perennials or perennials weeds to prevent more seeds from biennials developing. Annual weeds are Vegetative phenomenally prodigious seed producers. < 1 year 2 to a few years Long, indefinite lifespan  A single crabgrass plant, for example, Vegetative can produce 100,000 seeds No Accidental Yes reproduction  If you dont get rid of these intruders before they develop viable seeds, the Seed longevity Years to decades Years to decades A few years number of weed plants will increase Energy allocated every year, to seed High Medium high Low  Examples of annual weeds include: production bindweed, chickweed, crab grass, knotweed, lambs-quarters, mallow, Establishment Seeds Seeds Mainly vegetative pigweed, purslane, speedwell, spurge and Usual means of In soil, manure, Soil, wind, feces, yellow oxalis In soil dispersal equipment, wind crop seed  Your strategy: kill before they flower Lambsquarters, Quackgrass, Annual Sowthistle & set seed Examples Dandelion Annual Bluegrass bindweed Sonchus oleraceus © Project SOUND © Project SOUND Annual weeds, ancient wisdom Puncture vine - Tribulus terrestris  Characteristics:  Sharp, thorny burs  Grows in dry areas of garden  Growth form: herbaceous annual  How it spreads: seed  Control Methods:  Prevent introduction: sanitation  Hoe or dig plants before they can set seed; cut below the crown to prevent regrowth.  Chemical control: pre-emergence herbicides containing trifluralin or pendimethalin may  Getting weeds out of the garden at the start of the season, be used on some lawn grasses and when theyre most vulnerable, is a smart strategy: it is easiest ornamentals. For post-emergence control in then & it keeps annual weeds from forming seed heads lawns, use a selective herbicide containing MCPA, MCPP, and dicamba. © Project SOUND © Project SOUND 12
  • 13. 1/7/2013 Vigilance is the key Crabgrass - Digitaria species  The only way to control annual weeds is to get rid of them before  Characteristics: they go to seed. Luckily annual  Thrives in hot moist areas – lawns, weeds are very often shallow flower gardens rooted and can be easily hand  Shallow-rooted pulled or cut off with a hoe.  Growth form: annual grass  Hopefully you will see less and less annual weeds as the season goes  How it spreads: seed along, but new seeds will always find their way in and some seeds  Control Methods: remain dormant in the soil until ideal conditions present  Pull before it sets seed. themselves and they germinate, so  Water deeply, but infrequently; this weeding is an ongoing process. tactic will dry out crabgrass roots, killing the weeds or at least diminishing their vigor.If you get in the habit of doing a little weeding each time you  Solarization can control crabgrass ifwork in your garden – or even every day - it won’t become an high temperatures are achieved.overwhelming task (this is known as the ‘Bradley Method’. © Project SOUND © Project SOUND Crabgrass - Digitaria species Control methods: mechanical  Control Methods:  Hoeing is by far the easiest  For chemical control in lawns and  Draw Hoe - the familiar flat- around ornamentals, use a pre- bladed hoe works best when pulled. emergence herbicide such as With a sharp blade, you can make trifluralin; apply it in late winter to quick work of the long rows early spring, depending on when between vegetable crops. crabgrass germinates in your zone (a local nursery or your Cooperative  Warren Hoe - has a pointed blade rics_3.htm Extension Office can provide this heart-shaped blade that is usually information). For post-emergence used for creating furrows but also control around ornamentals, apply works well for small weeds and fluazifop-butyl or sethoxydim. weeding between rows.  Scuffle, Stirrup, Hoola or Dutch Hoe - Cuts weeds at the surface in a push/pull motion. Easy to use and nice for covering a larger area. © Project SOUND © Project SOUND 13
  • 14. 1/7/2013 Control methods: mechanical Control methods: mechanical  Hand pulling/digging  Good for small numbers of weeds  Allows you to get the roots out (important for some perennial weeds)  The easiest and most convenient weeder is your hand.  It becomes second nature to yank a weed or two every time you walk plants/how-to-weed-your-garden-in-spring-and-summer.htm outdoors.  Hand pulling is also the best method for a densely planted garden bed that has been neglected.  Wide variety of hand tools – try them out to see what works best for you © Project SOUND © Project SOUND  The Heart Hoe with its singleClassical weeding tools edge thin blade is for ridding your garden of unwanted weeds Spotted Spurge - Chamaesyce (Euphorbia) maculata and roots. It also is handy for weeding the cracks in the sidewalk and driveway.  Characteristics:  The Claw is excellent for  prostrate, often forming dense mats cultivating flower beds and  Broken stems emit a milky sap vegetable gardens.  The Cape Cod Weeder has an  Growth form: herbaceous annual angled blade that removes weeds (summer) below the surface of the soil. This tool will also handle those weeds in the cracks of sidewalks  How it spreads: seed and driveways.  Control Methods:The Weed Slicer (Dutch Hoe) cuts off weeds at the roots with little soil disturbance  Prevent it’s entry into the garden – good prevention methodsThe Diamond Hoe has an unique diamond-shaped blade for cultivating soil, dislodgingweeds and roots, or breaking up clumps of dirt.  Solarization prior to planting to kill seedsThe Trowel is for digging; The Transplanting Trowel has a narrower blade for precisedigging in any garden. It is very good for tight spaces, planting bulbs or fitting  Mulching to prevent germinationtransplants into a full bed.  Hand pullingThe Dandelion Weeder is for getting under weeds with tap roots, like dandelions, and  Only if these fail do you resort toprying them out. chemical methods © Project SOUND © Project SOUND 14
  • 15. 1/7/2013 Annual Bluegrass - Poa annua Integrated Pest Management (IPM)  Characteristics: Mechanical/Physical Controls – other  Bunching grass  Great seeder  Flaming  Done with a high flame temp. torch;  Growth form: annual grass (cool-season)  Plants are not burned but ‘boiled’  Not very effective with grasses  How it spreads: seeds  Be careful to not ignite mulch  Control Methods:  Foaming –  Avoid bringing into garden – particularly  Hot-foam and steaming is mainly done in nursery pots, on equipment, clothing by professionals; cool foams are  Mulch - coarse, thick to block light available (Weed B Gon & others)  Good selectivity – can ‘spot kill’  Limit water; Zone 2 or 1-2 – has shallow roots  No fire danger  Can’t use near water; kills fish  Mechanical weeding – before it seeds  Chemical methods – often not needed  Boiling water – good for weeds in pavement © Project SOUND © Project SOUND Integrated Pest Management (IPM) Consider buying Mechanical/Physical Controls, cont. some good tools  Mowing/cutting (e.g.,  If you do a lot of ‘weed-whacking’) weeding you’ll grow to  Good in large areas; better appreciate a good tool – than nothing works well & easier on  Ok for annuals prior to the body seeding; not so helpful for perennials  Tilling  Keep to a minimum – brings up new seeds in our climate  Newer technologies  Lasers – now being tested in agriculture Radius Garden Weeder © Project SOUND © Project SOUND 15
  • 16. 1/7/2013 What the pro’s like…. Perennial Weeds  Asparagus knife  Live more than a single season.  Hori-hori knife  Usually reproduce both by seeds  Fiskars ‘Big Grip Knife’ and vegetative reproduction (underground root systems (~$10) (rhizomes) and/or sending out runners (stollons) aboveground.  Are the most difficult to get rid of in the garden.  Examples include: bindweed, nutsedges, dandelion, dock, ground ivy, horsetail, Japanese knotweed, plantain, poison ivy, Bermuda grass, etc.  some weeds that are annuals in other climates are short-lived perennials in ours (Ex: Cheeseweed) © Project SOUND © Project SOUND Cheese Weed - Malva neglecta Some weedy invasive perennial grasses spread via  Characteristics: seed alone  long, tough taproot  Growth form: herbaceous short-lived perennial (in our climate)  How it spreads: seed  Control Methods:  Hoe or pull these weeds when theyre young.  Chemical control: Pampas Grass - Cortaderia selloana  pre-emergence herbicide containing isoxaben to prevent seedlings from becoming established in lawns and around ornamentals.  post-emergence control in lawns, use a product containing MCPA, MCPP, and dicamba.  Spot-treat young weeds with an herbicide containing glufosinate-ammonium or lyphosate, Fountain Grass – Pennisetum setaceum avoiding contact with desirable plants. Mexican Feather Grass – Nassella © Project SOUND (Stipa) tenuisima © Project SOUND 16
  • 17. 1/7/2013 But most have modified roots & stems Weeding Perennial Weeds that help them to thrive  If you catch them young, perennial weeds can usually be pulled out of the ground easily.  Runners (stolons): A well known example of that would be crabgrass. It spreads with creeping stems that grow along  Once established, they can be next to impossible to get rid of, as the ground. Buds along the runners produce plantlets that anyone who has battled Bermuda grass or yellow nutsedge in root and spread very quickly flower beds will attest.  Roots or Rhizomes: Quackgrass would fall into this  With perennials, it is essential to get all of the plant out of the category. It has tough, white rhizomes that look like roots ground. When perennial weeds are tender seedlings, they can and are very sharp. Weeds that spread by roots or usually be pulled up by hand with ease, especially when the soil is rhizomes can regrow after being cut back. Even chopped up moist. But the more time you allow these weeds to take hold, the pieces of root or rhizome may regrow. harder they are to eradicate. The least bit of Bermuda grass rhizome left behind can sprout into a new plant.  Bulbs and bulbils: An example of this is a spiky grass called nutsedge. It has tubers or little bulbs that break off when  The best time to weed is shortly after a rain or an irrigation you pull the grass therefore never eliminating the cycle. Hand-pulling is the quickest method. If the weeds dont plant. They can pop up over night (again and again and yield easily or if they detach from the roots when you pull, again...!). switch to a trowel or dandelion weeder and dig or pry them out. © Project SOUND © Project SOUND Special management strategies for perennials  Exhaust the roots by continual cutting/hoeing  Remove roots/rhizomes or other reproductive organs from the soil‘Weed Twister vs. Tree of Heaven © Project SOUND © Project SOUND 17
  • 18. 1/7/2013 Yellow (Creeping) Woodsorrel - Oxalis corniculata  Characteristics:  Very aggressive invader  Sun or shade  Growth form: herbaceous perennial with fleshy taproot  How it spreads: seed (propelled to 6 ft); shallow, spreading root system Burmuda Buttercup : Oxalis pes-caprae  Control Methods:  Hoeing and tilling are not good choices for removing perennial  Dig out small plants before they set weeds. seed.  Hand weeding will work if you are very thorough about getting  Water deeply but infrequently the whole plant and root system.  Sometimes herbicides are the only solution for eradicating tough perennial weeds like poison ivy, ground ivy and brambles. © Project SOUND © Project SOUND Integrated Pest Management (IPM) Yellow (Creeping) Woodsorrel - Oxalis corniculata Biological controls  The use of plant-feeding insects, pathogens, or diseases that are host- specific to a noxious or invasive weed species, with the intention of  Control Methods: suppressing the weed’s population to an acceptable level.  Biological control does not intend to eradicate the target weed species, but instead is used to bring the plant into balance with the rest of the landscape.  For chemical control, use a pre- It is important to note that successful biological control agents are specific to the plant they are intended to control. In other words, the biological control emergence herbicide containing agent feeds and develops only on the intended weed species. Therefore, the oryzalin or pendimethalin to risk to other plants and organisms in the ecosystem is minimal. prevent seeds from germinating  Examples: Large herbivores: sheep, goats and becoming established. Spot-   Weed-specific pests (insects) treat oxalis in garden areas with  Example: releasing weevils that eat the seed of musk thistle; Releasing an insect whose larvae eat the roots of the weed. glyphosate, taking care to avoid -Releasing a round worm (nematode) or a mite that causes a gall (swelling) on the plant. -Infecting the weeds with specific fungi that damage that weed. contact with desirable plants  Potential problems: loss of specificity; toxicity of other control methods to the insects  Weed-specific diseases  Example: Puccinia rust can be used to control nutsedge  Lots of interest/research but not much application to garden yet © Project SOUND © Project SOUND 18
  • 19. 1/7/2013 Integrated Pest Management (IPM) Chemical controls Control methods: ‘Safe Organic’ pre- emergents with corn gluten meal  Non-biologics  ‘Safer ‘Concern’ - Contains corn gluten meal (84%) and  Vinegar mixed with a little dish soap sulfate (16%)  Non-selective – don’t get it on things  Application Recommendations:Apply 10-20 lbs. per 1000 you want square feet in the Spring & Fall for pre-emergent protection. Weed Prevention Plus is granulated and easy to  Works best on young weeds apply with a spreader or you can apply with the 5 lb. shaker bag to small garden areas. Homogenous pellet provides  Salt – best for weeds in pavement uniform nutrient and herbicide distribution. This product can also be applied as a regular nitrogen fertilizer in the Summer.  Recommended for the control of curlydock, purslane, clover,  Biologics dandelions, crabgrass and many other common weeds. Proper application provides up to 90% effective weed control in the  Example: AAL-Toxin (isolated from first year for dandelions and crabgrass. Safe for children, the pathogenic fungi, Alternaria a pets and wildlife immediately after application. Can be applied at any time without burning. Water thoroughly after lternata f. sp. lycopersici ) - Highly application then allow to dry for 2-3 days. susceptible species include such important agricultural weeds as black nightshade © Project SOUND © Project SOUND Some pesticide definitions Some pesticide definitions Preemergence Herbicides  Selective postemergence herbicides  are usually used to control annual,  Preemergence herbicides affect germinating seeds. biennial, and perennial broad-leaved  To be effective, the herbicide should be applied two to three weeks weeds because they will kill many before weed seeds germinate. broadleaf plants without damaging grass plants.  Consequently, preemergence herbicides are most effective against  There are also selective herbicides annual weeds. that kill only grasses Postemergence Herbicides  Nonselective postemergence herbicides  Postemergence herbicides are used to kill weeds after the weed  kill all plants, both desirable and plants are up and growing. undesirable.  To be effective, most postemergence herbicides must be absorbed  These herbicides can be used to spot through the leaves; consequently, liquid sprays generally work better treat perennial grassy weeds that than dry, granular materials. are not affected by selective herbicides.  Postemergence herbicides are most effectively applied when weeds  To spot treat an area, thoroughly wet are young and growing vigorously. the weed foliage with herbicide solution.  For some weeds, repeated application at 20–30 day intervals may be required for control. © Project SOUND © Project SOUND 19
  • 20. 1/7/2013 Herbicides: pre-emergent How do herbicides work Pre-emergent  Last 6-12 months Post-emergent  Block key chemical pathways in the plant: plant hormones; chemicals needed for photosynthesis  Inhibit basic cell functions: cell division; production of key chemicals © Project SOUND © Project SOUND Yellow nutsedge - Cyperus esculentus Herbicides – post-emergent  Characteristics:  Looks like a sedge  Grows in moist areas  Growth form: perennial sedge (summer)  How it spreads: seed; tubers (nutlets) from roots  Control Methods:  Remove when young ― < 6 inches tall. Older, taller plants are mature enough to produce tubers; when you dig or pull the plant, the tubers remain in the soil to sprout.  For chemical control, try glyphosate, being careful not to get the chemical on desirable plants. It is most effective when the plants are young; it will not kill tubers that have become detached from the treated plant © Project SOUND © Project SOUND 20
  • 21. 1/7/2013 Bindweed - Convolvulus arvensis Bindweed - Convolvulus arvensis  Characteristics:  Control Methods:  Also called wild morning glory, bindweed  For chemical control, you can use a pre- grows in open areas usually in loam to clay emergence herbicide containing trifluralin soils around ornamentals. In midsummer, when  Growth form: perennial vine from deep root bindweed is at the height of its growth season but has not yet set seed, spot-treat  How it spreads: isolated patches with glyphosate, taking  Bindweed is deep rooted, so pulling care to avoid contact with desirable plants. usually doesnt eradicate it ― the stems If the weed is twined around desirable break off, but the weed returns from the plants, detach it before treating. Repeated roots. applications are usually needed to destroy  Control Methods: the root system.  Dig the roots out repeatedly (persistence is required).  Prevent seeding: hard-coated seeds can sprout even after lying dormant in the soil for 50 years! © Project SOUND © Project SOUND Bermuda Grass - Cynodon dactylon Bermuda Grass - Cynodon dactylon  Characteristics:  Control Methods:  A fine-textured and fast-growing  Dig up stray clumps before they form perennial, frequently planted as a lawn sod, being sure to remove all the underground stems; any left behind can  Growth form: perennial grass (summer) start new shoots. Repeated pulling and digging are generally necessary to stop  How it spreads: spreads by underground this weed; mulches will slow it down, but stems (rhizomes), above ground runners it eventually grows through most of them. (stolons), and seed.  For chemical control, you can use a selective herbicide containing fluazifop-  Control Methods: butyl or sethoxydim, which can be  If you have a Bermuda grass lawn, use sprayed over some ornamentals. Spot- deep barriers or edging to prevent it treat actively growing Bermuda grass from advancing into other parts of the with glyphosate, taking care not to get garden. the chemical on desirable plants. © Project SOUND © Project SOUND 21
  • 22. 1/7/2013 Other weedy grasses that spread via Safety precautions when using herbicides seed and rhizomes  Read and follow all package instructions  Provide adequate ventilation and wear a respirator, rubber gloves, goggles, and protective clothing when handling.  Remove contaminated clothing and launder prior to reuse.  Shower after completing the job.  Wash hands with soap and water before eating, smoking, or using the toilet.  Store in a secure, dry, well-ventilated, separateQuack grass - Elytrigia repens Panic Veldt Grass - Ehrharta erecta Kikuyugrass - room, building or covered area Pennisetum clandestinum © Project SOUND © Project SOUND  Most herbicides become less effective when a  Fall is a good time to apply systemic herbicides to manage perennial weeds. These weeds have perennating organs like rhizomes and stolons that help plant is under stress. Along with crops, most them persist year after year. Development of these organs usually occurs during the early fall. During a drought, it is possible that drought tolerant weeds are also experiencing water stress under perennial weeds are more prevalent in fields than annual weeds. Therefore, fall may be a good time to apply a systemic herbicide (an herbicide that is current conditions. Therefore, you may have to absorbed and moved within the plant tissues). A non-selective systemic wait until the soil is fairly moist before applying herbicide like glyphosate could be applied as a spot application. Grass killers (graminicides) like sethoxydim, clethodim or fluazifop may also be applied any systemic herbicides (e.g., Roundup) to manage during fall to manage perennial grasses. weeds.  The main key to control of perennial weeds is application of glyphosate,  Most systemic herbicides perform better under dicamba (Banvel), and/or 2,4-D when they are are in the bud to bloom stage, or as late in the fall as possible before the weeds senesce or growth ceases conditions that are ideal for weed growth. When due to frost or freeze. At this growth stage, the weeds will move herbicide throughout the plant and into the roots, resulting in maximum kill of the the plants are free of stress, herbicides are entire plant. The best opportunity for making this type of application is absorbed faster and move better within the plant during the late-summer through fall after wheat harvest when plants have grown undisturbed for several months. system, providing more efficient kill. © Project SOUND © Project SOUND 22
  • 23. 1/7/2013 Summary: Identifying a weed will allow you to choose the best strategy to prevent its Potential problems with use of herbicides spread  Annual weeds – reproductive strategy: seeds  Cost  Key – prevent seed production  Herbicide-resistant weeds. The evolution  Biennial/non-spreading weeds – reproductive strategy: seeds  Removal (mechanical best) – hopefully when young (year 1) of "superweeds" capable of resisting  Prevent seed production – year 2 herbicides  Perennial weeds – reproductive strategy: seeds, vegetative  Removal – hopefully when young (year 1)  Prevent seed production and/or other primary means of reproduction  May need to use chemical controls – but only after other means are exhausted  Use UC IPC website for up-to-date management recommendations © Project SOUND © Project SOUND Advice from pros: The ABC’s of Weeding What is a noxious weed?  Learn how the weeds spread (root system or seed dispersal) to understand when and how to handle  Invasive alien plant: an invasive them. unwanted non-native plant  Keep cultivation/tilling to a minimum  According to The Flora of North America, the most comprehensive  Get the weeds early before they reference on this continents plants, flower and go to seed. one-fifth to one-third of all species growing north of Mexico have come  Get ‘em while they’re small. from other continents.  Frequent, short weeding sessions are  Noxious weed: any species of the best way to stay on top of plant which is, or is likely to be, weeds. Not only does this eliminate aRepetition is the key to long, tiring weeding session, it also detrimental or destructive andcombating persistent weeds.Even tough weeds such as lets you dispatch weeds while they’re difficult to control or eradicate still small and easy to eliminate.bindweed and kikuyu grass can  We are located in the Los Angelesbe brought under control with  Weed wet. Weeding goes faster and Weed Management area – reportcareful and fastidious weeding easier when the soil is moist than noxious weed infestations to thempractices. when the soil is dry © Project SOUND © Project SOUND 23
  • 24. 1/7/2013 Comparison of common weedy plants In natural areas (and in your garden ecosystem), and invasive plants. noxious weeds impact native ecosystems by: Agricultural or garden weeds Invasive plants  Reducing biodiversity Introduction Usually accidental by people, Can be accidental, but more often animals, equipment, or seed the original intention was for  Altering hydrologic (water) & soil contamination. ornamental or aquarium use, or for conditions forage, food, fiber, medicinal, or soil stabilization purposes.  Altering fire intensity and Disturbance Require human disturbance to Benefit from human disturbance, but frequency establish and persist. disturbance not required.  Modifying successional pathways Persistence Will not persist without human Once introduced, plants survive and disturbance, usually soil tillage or spread on their own without further  Competing for pollinators irrigation. human assistance.  Displacing rare plant species Life form Primarily terrestrial annuals or All growth forms, including aquatic,  Replacing complex communities herbaceous perennial species. climbing vines, parasitic, herbaceous, or woody plants. Can have annual, biennial, or perennial with simple communities life cycles. © Project SOUND Cheat Grass – Bromus tectorum © Project SOUND Characteristics of invasive plants: general What you can do about invasive weedy plants in S. CA  Fast, aggressive growth that robs soil, water and nutrients from desirable plants nearby. 1. Know what species  Quick adaptation to the existing are a problem in environment. your area  Ability to thrive in disturbed areas (wet or dry) and poor soil. 2. Get rid of these  Resistance to heat and drought. plants in your yard  Deep, strong roots making them difficult to 3. ‘Don’t Plant a Pest’ eradicate. 4. Report infestations  Lack of natural pest or predator. Invasive 5. Lobby to get weedy species seldom show signs of disease or pest damage. pest plants out ofCoast Acacia – Acacia cyclops the horticultural  Some invasive species are able to produce trade toxins that inhibit competitors growth. © Project SOUND © Project SOUND 24
  • 25. 1/7/2013 Where to learn more about invasive Don’t Plant a Pest  Iceplant/hottentot fig (Carpobrotus edulis) plants…  Ivy (Hedera spp.)  Periwinkle (Vinca major)  Pampas grass (Cortaderia selloana)  Fountain grass (Pennisetum setaceum)  Scotch, French, Portugese, bridal, and Spanish brooms  Acacia/western coastal wattle (Acacia cyclops) Acacia  Myoporum (Myoporum laetum)  Mexican fan palm (Washingtonia robusta)  Canary island date palm (Phoenix canariensis)  Brazilian pepper tree (Schinus terebinthifolius)  Blue-gum and red-gum eucalyptus (Eucalyptus globulus, E. camuldulensis)  Tree of Heaven - Ailanthus altissima © Project SOUND © Project SOUND MyoporumI thought that was a native plant…  Some native plants can ‘take Climate change & invasive plants over’ and become weedy or invasive:  ‘groundcover’ natives that  Gardeners may also have to cope with a new cast of characters. spread via rhizomes Some researchers are trying to identify exotic species with weed [Woodmints] or stolons potential before they jump the garden fence - plants with [native strawberries] windblown or bird-dispersed seeds, species that reproduce vegetatively through runners, generalists that thrive in a variety of  Clonal species [Narrow-leaf habitats - and working with growers and nursery folk to make sure Willow; some of the shrubby new invasives dont get into the horticultural trade. native mallows]  Plants that grow very fast  Climate change is a moving target, and some effects could turn out [Calystegia] to be stronger than the models account for. Theres also no  Plants that reseed very well in foolproof way to identify which plants will become invasives. But your yard [grasses; some with weeds moving both in from wildlands and out into them, its wildflowers] safe to say that weed control will still be on every thoughtful gardeners agenda.  Know the characteristics;  plant where you take advantage of these characteristics – e.g., where you want them to take over © Project SOUND © Project SOUND 25
  • 26. 1/7/2013“When you want to shift your ch’i (energy), go to your garden and start pulling weeds.” © Project SOUND 26