Garden Weeds - notes


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Garden Weeds - notes

  1. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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