weeds 2009

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© Project SOUND Out of the Wilds and Into Your Garden Gardening with Western L.A. County Native Plants Project SOUND - 2009

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This lecture was given in September, 2009 as part of the California native plant gardening series ‘Out of the Wilds and Into Your Garden’

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Page 1: Weeds   2009

© Project SOUND

Out of the Wilds and Into Your Garden

Gardening with Western L.A. County Native Plants Project SOUND - 2009

Page 2: Weeds   2009

© Project SOUND

Weeds & More

Weeds

C.M. Vadheim and T. Drake

CSUDH & Madrona Marsh Preserve

Madrona Marsh Preserve

September 5th 2009

Page 3: Weeds   2009

© Project SOUND

Does this look like your garden?

You’re not alone – weeds

are a perennial concern in

S. California gardens!

http://www.entrepreneurs-journey.com/824/how-i-made-six-figures-in-one-day/

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What is a weed? (definition)

Weed: any plant that is growing at a site where it is not wanted

http://www.progardenbiz.com/wp/weeds-who-they-are-and-what-they-tell-us/

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Why control weeds? (it’s a war out there!)

Weeds compete with desirable plants for: Light Water Nutrients Space

Weeds also provide hiding places for insects and serve as a source of plant diseases.

Weeds can kill a gardener’s enthusiasm, which can cause them to abandon the garden; Game ends – weeds win

http://www.nature.org/wherewework/northamerica/states/hawaii/

projectprofiles/art26290.html

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Weeds are particularly challenging in W. L.A. County

No killing frosts or smothering snow; weeds that are annuals in many climates are perennial in ours

No killing high temperatures

People water a lot (up to now)

Lots of weedy plants to spread their seeds/invade via roots

Use of ‘mow & blow’ gardeners – weeds hitch-hike between gardens

http://acwm.co.la.ca.us//scripts/wma_4.htm#F

Castor Bean ( Ricinus communis)

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Where do alien weeds come from?

Many of California’s noxious and invasive weeds came from regions with comparable climates in the Mediterranean region, Australia, S. Africa

Others, including many garden weeds come from nearly all parts of the globe, including particularly western and central Asia, Russia & Europe

They were introduced through human activity, both accidentally and intentionally, including by gardeners.

http://www.grabovrat.com/mapsViews/mapsViews80.html

Mediterranean Climate Zones

Percentage of invasive plants accidentally or

intentionally introduced to California.

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pni74139-2.html

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Weeds tell a story….

Type of soil – some prefer certain soil characteristics

Available light

Soil nutrient levels (low or high)

Watering practices

Cultivation practices – how much the soil is disturbed

And many other things To know a weed is to

learn about your garden –

and to understand how to

combat it!

Page 9: Weeds   2009

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The more you know about your garden’s own weeds, the better you

will be able to deal with them

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In the garden (and in the operating room), first do no harm

Your plan to combat weeds should be reasonable and

environmentally friendly

Page 11: Weeds   2009

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Integrated Pest Management (IPM)

"Optimum combination of control methods including biological, cultural, mechanical, physical and/or chemical controls to reduce pest populations to an economical acceptable level with as few harmful effects as possible on the environment and nontarget organisms."

R.L. Hix,CA Agric. Magazine, 55:4 (2001)

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The IPM Pyramid – ‘first do no harm’

Use the least invasive – and often most effective - means first: Prevention – cultural

practices Mechanical Controls Naturally occurring

biological controls (native)

Consider using non-native biological controls (herbivores; diseases)

Use chemical controls sparingly, as a last resort: Naturally occurring elements Biologics – chemicals made

by plants that are toxic to weeds

Non-biologic herbicides

http://www.team.ars.usda.gov/ipm.html

Non-native and chemical controls may

have the important drawback of non-

specificity – they kill the good species

along with the bad.

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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 conditions indicate that pest control action must be taken. The level at which pests will either become an economic threat is critical to guide future pest control decisions.

2. Monitor and Identify Pests Not all insects, weeds, and other living organisms require control.

IPM programs work to monitor for pests and identify them accurately, so that appropriate control decisions can be made in conjunction with action thresholds. This monitoring and 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.

3. Preventive Cultural Practices As a first line of pest control, IPM programs work to manage the

crop, lawn, or indoor space to prevent pests from becoming a threat. These control methods can be very effective and cost-efficient and present little to no risk to people or the environment.

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An IPM system is designed around six

basic components

4. Mechanical controls: Should a pest reach an unacceptable level, mechanical methods are the first options to consider. They include simple hand-weeding, erecting weed barriers, and tillage to disrupt breeding.

5. Biological controls: Natural biological processes and materials can

provide control, with minimal environmental impact, and often at low cost. The main focus here is on promoting beneficial herbivores that eat target pests. Use of plant pathogens – ones specific to the weeds of interest - also fits in this category.

6. Chemical controls: Synthetic pesticides are generally only used

as required and often only at specific times in a pests life cycle. Many of the newer pesticide groups are derived from plants or naturally occurring substances (e.g.: allelopathic analogues), and further 'biology-based' or 'ecological' techniques are under evaluation (particularly for agriculture, forestry applications).

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Integrated Pest Management (IPM)

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

http://www.statuaryplace.com/store/index.php?main_

page=index&cPath=46

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If you can, do a little bit – but do it consistently

Weeding just 15-30 minutes a day is often all that’s needed

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Integrated Pest Management (IPM)

Monitor and Identify Weeds

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. Examples: Annual Bluegrass, Bermuda

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 Examples: Creeping Woodsorrel (Oxalis) ;

Cool season weed

Annual Bluegrass – Poa annua

http://www.dynamiteexterminators.com/WeedFacts.html

Warm season weed

Crabgrass – Digitaria species

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Climate change: long periods of hot weather during winter rains

Favors growth of many weeds: jump-start on growth season Example: Panic Veldt Grass - Ehrharta erecta

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Integrated Pest Management (IPM)

Monitor and Identify Weeds

Get to know the geography of your garden’s weeds

Areas prone to weeds require special monitoring & early intervention

Discovering geographic patterns may suggest changes in gardening practices – decreasing water to the area; increased hand-weeding frequency; etc.

Know that wildlife (birds, etc) will bring seed into your yard. Be extra vigilant in areas where they eat, perch etc.

Oxalis/ Creeping Woodsorrel

Oxalis corniculata

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Each garden is unique: garden weeds in context

Soil (including previous amendments)

Light & water

Gardening practices: tilling, raking, mulches, ‘top soil’, hired gardener’s practices

The age of the garden (or part of the garden)

Previous (and current) plants Weeds that hitch-hike in with purchased

plants Invasive garden plants [ivy; bamboo;

dichondra; etc]

What’s growing nearby: Birds bring seeds; seeds blow Weeds grow into the yard

We will introduce you to some general principles, strategies and tools

that you can apply to your own situation

Dichondra

Dichondra micrantha

(Dichondra repens)

Page 21: Weeds   2009

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Garden weeds may vary widely from year to year…

Example: Shepherd’s Purse (Capsella bursa-pastoris)

Why?

Conditions are right for germination of dormant seeds; temperature; rainfall

Seeds survive up to 35 years in undisturbed soils

When conditions are right – they are ready

New seeds may have been brought in by gardening practices

New seeds may have come in through natural means; wind, birds, etc.

http://www.plant-identification.co.uk/skye/cruciferae/capsella-bursa-pastoris.htm

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The Weed IPM plan for your garden – a

work in progress

Requires observation & knowledge – specific for your garden

Will vary somewhat with: Yearly weather conditions Maturity of plants New plants, and other

changes to the garden

Will be modified based on your previous experiences

Suggestion: keep a garden notebook/journal

http://www.hoodcountymastergardeners.org/Demo_2006/Demo_Construction.html

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Identifying weeds 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 press them - as you find them; makes 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

Kikuyu grass

Pennisetum clandestinum

http://www.hear.org/starr/plants/images/image/?q=061205-1921

http://www.tropicalgrasslands.asn.au/pastures/kikuyu.htm

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Great resources on-line & in books

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Identifying weeds is key to your weed strategy

Knowing the ID of a weed will tell you:

Growth pattern – annual or perennial weed

Cool/warm season weed – when to look for it

How it likely enters your garden – suggests ways to prevent this

Useful mechanical/physical controls

Chemical controls (if needed)

http://www.earthlygarden.com/category/lawnmower-maintenance/

Kikuyu grass is used for lawns

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Integrated Pest Management (IPM)

Preventive Cultural Practices

The first line of defense against all weeds is good prevention

General goals:

Prevent the introduction of weeds into the garden

Prevent the spread of weeds in the garden

Promote the health & vigor of desired species

‘An once of prevention is worth a pound of cure’ – simple preventive practices can save you serious gardening headaches

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Common Purslane - Portulaca oleracea

Characteristics: Succulent foliage (healthy edible;

probably should be grown as a garden vegetable)

Grows in moist areas (usually)

Summer (warm season); origin - Asia

Growth form: herbaceous annual

How it spreads: seeds (> 50,000 per plant; stem pieces

Control Methods: Solarization for pre-planting removal.

Mulch & dry conditions usually prevent it from establishing

Easy to pull or hoe, but pieces of stem can re-root readily, so be sure to remove them from the garden.

http://www.ppws.vt.edu/scott/weed_id/porol.htm

http://commons.wikimedia.org/wiki/File:Portulaca_oleracea_stems.jpg

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Prevention/Cultural Practices – avoidance/

prevention is key

Avoid introducing new weeds into the garden:

Use only weed-free mulch, topsoil, other amendments (if any); beware of ‘free’ material unless you know it will not contain weeds/weed seeds

Check new plants to be sure that weeds are not ‘hitchhiking’ in the pots

Be sure to not bring weed seeds into garden on your clothes, shoes, etc.

http://asimpleyarn.net/category/garden-on-tuesday/

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Sanitation

Clean equipment (including lawnmowers) to prevent spread of weed seeds/cuttings

Weed Disposal: Annual weeds can be composted if

they are not in seed.

Place perennial weeds in a garbage bag, solarize (leave bag in sun) & dispose of them in green waste.

If any weed is a big problem in your garden, think twice before putting it in the compost pile.

Cultural practices: just good old garden

management practices

http://www.norcalblogs.com/sustainable/2008/10/compost_

clueless.html

Note: a ‘hot’ compost bin will kill

some – but not all – weed seeds,

so be cautious

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Keep garden plants healthy; help them to out-compete the weeds

Plant native plants densely enough to crowd out weeds

Choose native plants that:

Are vigorous growers – will out-compete the weeds

Will prevent weeds from growing by:

Providing too much shade

Producing allelopathic chemicals that either inhibit weed seed germination or weed growth: examples: Salvias?, Chamise, Manzanitas, CA Walnut, probably other CSS species

Cultural practices: good garden management

Purple Sage – Salvia leucophylla

Page 31: Weeds   2009

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Integrated Pest Management (IPM)

Physical Prevention – 2nd line of prevention

Weeds have growth requirements - like any other plant:

Water

Correct amount of light

Correct temperature

Appropriate nutrients

Prevent seed germination & seedling growth by limiting the weed’s access to ‘growth requirements’

Remember: limit any one of these and you’ll significantly decrease the ability of a weed to take over your garden

Black Nightshade - Solanum nigrum

Page 32: Weeds   2009

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Fortunately, weeds need water to germinate

and grow

Water-wise gardening methods will limit some weeds, simply by decreasing available water

Particularly helpful for shallow-rooted weeds

Also useful for ‘weeds of wet places’ – will not survive in dry soil

Use target watering methods – water only the plants you want (drip; hose)

Be patient – first couple of years, when you need to water shrubs more, are the worst

Broadleaf Plantain - Plantago major

Page 33: Weeds   2009

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Broadleaf Plantain – Plantago major

Characteristics: Large leaves from basal rosette; originally

brought from Europe as medicinal plant

Usually in damp area of garden

Growth form: herbaceous perennial

How it spreads: seed

Control Methods: Crowd out; needs bare soil to germinate, grow

Decrease water; aerating the lawn will also help.

Dig out before they set seed. Be sure to remove as much of the roots as possible - can regrow from any pieces of the fibrous rootstalk that remain in the soil.

Chemical control -spot-treat with glyphosate (Roundup), taking care not to get the chemical on desirable plants.

http://www.wildflowers-and-

weeds.com/Plant_Families/Plantaginaceae.htm

You can use your knowledge of

a weed’s growth requirements

to save time and effort

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Before planting a new area…prevention

almost always better than control

Kill weed plants & seeds Solarization Chemical methods

Turn the soil as little as possible – avoid bringing up buried weed seeds

Control weeds before installation – always less work in the long run

Be patient – the more weeds/seeds are removed before installation, the fewer you’ll have to pull later

Bermuda Grass

Cynodon dactylon

http://earthlandscapes.blogspot.com/2008/02/how-to-choose-best-lawn-grass-2.html

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Understanding seeds: what seeds need to

germinate

Water – need to ‘re-hydrate’ before seedling can start to grow

Light (small seeds, including many weeds) or dark (larger seeds)

Correct temperature; may be warm or cool – and may be a rather narrow range. In general, weeds tend to have larger ranges, but many are ‘warm season’ or ‘cool season’ weeds

Other factors (heat; smoke; cold pre-treatment, etc): in general, weed seeds have few of these – it’s one of the reasons they are so successful

Virgin’s Bower - Clematis ligusticifolia

Native plant – requires cold treatment

Oxalis/ Creeping Woodsorrel

Oxalis corniculata

Weed – no special requirements

http://www.ars-grin.gov/npgs/images/sbml/?C=M%3BO=A

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Key preventive method: blocking sunlight

so light-requiring seeds can’t germinate

Mulches Organic

Inorganic

‘Weed block’ methods

Planting natives that will create shade

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Why barrier methods work: several effects Block light, preventing seed

germination

Physically prevent seedling growth

Reduce soil temperature – particularly in spring – delay emergence

Increase soil moisture below the barrier – too much for some species (seeds & seedlings rot)

Decrease moisture above the barrier – too dry for germination

Chemical compounds released from barriers/ mulch may inhibit germination and/or kill seedlings

http://landscaping.about.com/od/weedsdiseases/ss/weed_fabrics_6.htm

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Plastic weed barrier cloth (weed block) – is it good for native plant gardens?

Stop some weeds seeds from germinating; blocks light & forms physical barrier

Relatively easy to install

Doesn’t stop all weeds from growing Weeds grow through the holes cut for

planting Weeds grow through/on top of the

barrier cloth

Cloth gets clogged over time – becomes a water barrier

Can promote stem & root fungal disease in trees & shrubs; interferes with proper drainage

Doesn’t allow groundcover plants to root – or for successful re-seeding

Hard to keep from looking unsightly- even under mulch

Can’t be used well on slopes or other uneven terrain

Arguments for Arguments against

http://homeideas.howstuffworks.com/weeds-and-invasive-plants/weed-barrier-basics.htm

Page 39: Weeds   2009

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Physical barriers

have their place

Weedblock (plastic or other) Under pathways Under patios, sitting areas

(hardscaped areas) Other areas where planting is

not an option

Other physical barriers (e.g., mowing strip, heavy metal or wood strip set on edge) at shrub bed/turf interface to prevent turf and turf weeds from encroaching into planted beds

http://www.ndmnaturescapes.com/freshplanting.htm

You may also choose more eco-friendly barriers

Page 40: Weeds   2009

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Eco-friendly ‘weed

block’ choices

Newspaper (use a good thickness to block light)

Cardboard

Degradable weed block materials – most are paper-based

‘Garden Trail’ weed block

http://blueplanetgardening.com/sm-push-mulch-away.jpg

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What kinds of seeds

are susceptible to

‘dark inhibition’?

annual species that are small-seeded and have a light requirement for germination such as common lambsquarters and pigweeds are sensitive to surface barriers

large-seeded annuals and perennial weeds are relatively insensitive to the darkness; however barriers/mulches still provide mechanical barriers to seedling growth.

‘Garden Trail’ weed block

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Mulch – the best surface physical barrier

for native plant gardens

Kind of mulch

Should be appropriate for the native plants you’ve planted

Organic (bark, etc) for most local shrubs/trees

Inorganic for Coastal Prairie (wildflowers) and desert plants

Must be course enough texture to allow the mulch surface to dry out

Depth of mulch layer

Must be deep enough to prevent light from reaching the seeds beneath it.

Lesson: geography of weeds

suggests that mulch layer may be

too thin at the edge

Page 43: Weeds   2009

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IPM plan changes through the life of a garden/bed

Pre-planting: Prevention/removal

Pre-planting: Prevention/practices

Years 1-2: Monitoring & Removal

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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 it

How it likely enters your garden – suggests ways to prevent this

How it spreads

Useful mechanical/physical controls

Chemical controls (if needed)

Annual weed – Gnaphaleum sp.

Perennial weed - Oxalis pes-caprae

Page 45: Weeds   2009

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Annual, Biennial & Perennial Weeds

Character Annuals

Short-lived (fixed)

perennials or

biennials

Spreading

perennials

Vegetative

lifespan < 1 year 2 to a few years Long, indefinite

Vegetative

reproduction No Accidental Yes

Seed longevity Years to decades Years to decades A few years

Energy allocated

to seed

production

High Medium high Low

Establishment Seeds Seeds Mainly vegetative

Usual means of

dispersal

In soil, manure,

equipment, wind

Soil, wind, feces,

crop seed In soil

Examples Lambsquarters,

Annual Bluegrass Dandelion

Quackgrass,

bindweed http://www.css.cornell.edu/weedeco/WeedDatabase/index2.html

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Annual weeds Spread by seed. They may self-seed or they may be brought into the garden by wind, water, birds, animals or people.

The most important way combat annual weeds to prevent more seeds from developing. Annual weeds are phenomenally prodigious seed producers.

A single crabgrass plant, for example, can produce 100,000 seeds

If you don't get rid of these intruders before they develop viable seeds, the number of weed plants will increase every year,

Examples of annual weeds include: bindweed, chickweed, crab grass, knotweed, lambs-quarters, mallow, pigweed, purslane, speedwell, spurge and yellow oxalis

Your strategy: kill before they flower & set seed

Annual Sowthistle

Sonchus oleraceus

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Annual weeds, ancient wisdom

Getting weeds out of the garden at the start of the season,

when they're most vulnerable, is a smart strategy: it is easiest then & it keeps annual weeds from forming seed heads

http://www.backsavergrip.com/photos.htm

http://www.english.illinois.edu/maps/poets/a_f/erdrich/boarding/gallery.htm

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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 be used on some lawn grasses and ornamentals. For post-emergence control in lawns, use a selective herbicide containing MCPA, MCPP, and dicamba.

http://www.ppws.vt.edu/scott/weed_id/trbte.htm

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Vigilance is the key

The only way to control annual weeds is to get rid of them before they go to seed. Luckily annual weeds are very often shallow rooted and can be easily hand pulled or cut off with a hoe.

Hopefully you will see less and less annual weeds as the season goes along, but new seeds will always find their way in and some seeds remain dormant in the soil until ideal conditions present themselves and they germinate, so weeding is an ongoing process.

If you get in the habit of doing a little weeding each time you work in your garden – or even every day - it won’t become an overwhelming task (this is known as the ‘Bradley Method’.

http://www.frenchgardening.com/aujardin.html?pid=310620990670798

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Crabgrass - Digitaria species

Characteristics: Thrives in hot moist areas – lawns,

flower gardens

Shallow-rooted

Growth form: annual grass

How it spreads: seed

Control Methods: Pull before it sets seed.

Water deeply, but infrequently; this tactic will dry out crabgrass roots, killing the weeds or at least diminishing their vigor.

Solarization can control crabgrass if high temperatures are achieved.

http://www.ppws.vt.edu/scott/weed_id/digis.htm

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Crabgrass - Digitaria species

Control Methods: For chemical control in lawns and

around ornamentals, use a pre-emergence herbicide such as trifluralin; apply it in late winter to early spring, depending on when crabgrass germinates in your zone (a local nursery or your Cooperative Extension Office can provide this information). For post-emergence control around ornamentals, apply

fluazifop-butyl or sethoxydim.

http://www.ppws.vt.edu/scott/weed_id/digsa.htm

http://www.aragriculture.org/horticulture/ornamentals/weed_id/crabgrass.htm

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Control methods: mechanical

Hoeing is by far the easiest

Draw Hoe - the familiar flat-bladed hoe works best when pulled. With a sharp blade, you can make quick work of the long rows between vegetable crops.

Warren Hoe - has a pointed blade heart-shaped blade that is usually used for creating furrows but also works well for small weeds and 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.

http://landscaping.about.com/od/weedsdiseases/ss/weed_fab

rics_3.htm

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Control methods: mechanical

http://landscaping.about.com/od/weedsdiseases/ss/weed_fabrics_3.htm

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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 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

http://www.sujutools.com/image/gardentool2.jpg

http://homeideas.howstuffworks.com/weeds-and-invasive-

plants/how-to-weed-your-garden-in-spring-and-summer.htm

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Classical weeding tools The Heart Hoe with its single edge thin blade is for ridding your garden of unwanted weeds and roots. It also is handy for weeding the cracks in the sidewalk and driveway.

The Claw is excellent for cultivating flower beds and vegetable gardens.

The Cape Cod Weeder has an angled blade that removes weeds below the surface of the soil. This tool will also handle those weeds in the cracks of sidewalks and driveways.

http://yardener.com/YardenersToolshedofProducts/HandTools/HandToolsForLawnCare/HandToolsForWeeding/WeedersbySnowNealley

The Weed Slicer (Dutch Hoe) cuts off weeds at the roots with little soil disturbance

The Diamond Hoe has an unique diamond-shaped blade for cultivating soil, dislodging weeds and roots, or breaking up clumps of dirt.

The Trowel is for digging; The Transplanting Trowel has a narrower blade for precise digging in any garden. It is very good for tight spaces, planting bulbs or fitting transplants into a full bed.

The Dandelion Weeder is for getting under weeds with tap roots, like dandelions, and prying them out.

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Spotted Spurge - Chamaesyce (Euphorbia) maculata

Characteristics: prostrate, often forming dense mats

Broken stems emit a milky sap

Growth form: herbaceous annual (summer)

How it spreads: seed

Control Methods: Prevent it’s entry into the garden –

good prevention methods

Solarization prior to planting to kill seeds

Mulching to prevent germination

Hand pulling

Only if these fail do you resort to chemical methods

http://www.aragriculture.org/horticulture/ornamentals/weed_id/spurge_spotted.htm

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Annual Bluegrass - Poa annua

Characteristics: Bunching grass

Great seeder

Growth form: annual grass (cool-season)

How it spreads: seeds

Control Methods: Avoid bringing into garden – particularly

in nursery pots, on equipment, clothing

Mulch - coarse, thick to block light

Limit water; Zone 2 or 1-2 – has shallow roots

Mechanical weeding – before it seeds

Chemical methods – often not needed

http://www.aragriculture.org/horticulture/ornamentals/weed_id/bluegrass_a

nnual.htm

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Integrated Pest Management (IPM)

Mechanical/Physical Controls – other

Flaming Done with a high flame temp. torch; Plants are not burned but ‘boiled’ Not very effective with grasses Be careful to not ignite mulch

Foaming – Hot-foam and steaming is mainly done

by professionals; cool foams are available (Weed B Gon & others)

Good selectivity – can ‘spot kill’ No fire danger Can’t use near water; kills fish

Boiling water – good for weeds in pavement

http://yardener.com/FlamingWeedTools.html

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Integrated Pest Management (IPM)

Mechanical/Physical Controls, cont.

Mowing/cutting (e.g., ‘weed-whacking’) Good in large areas; better

than nothing Ok for annuals prior to

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

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Consider buying some good tools

If you do a lot of weeding you’ll grow to appreciate a good tool – works well & easier on the body

http://ergonomics.about.com/od/gardeningequipment/ss/useradtools_7.htm

Radius Garden Weeder

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What the pro’s like….

Asparagus knife Hori-hori knife Fiskars ‘Big Grip Knife’

(~$10)

http://www.fine-tools.com/garten.htm

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Perennial Weeds

Live more than a single season.

Usually reproduce both by seeds and vegetative reproduction (underground root systems (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)

http://www.zum.de/stueber/lindman/234.jpg

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Cheese Weed - Malva neglecta Characteristics:

long, tough taproot

Growth form: herbaceous short-lived perennial (in our climate)

How it spreads: seed

Control Methods: Hoe or pull these weeds when they're young.

Chemical control: 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,

avoiding contact with desirable plants.

http://jeantosti.com/fleurs3/

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Some weedy invasive perennial grasses spread via seed alone

http://www.hotgardens.net/Blooming_Pampas_Grass.JPG

Pampas Grass - Cortaderia selloana

Mexican Feather Grass – Nassella

(Stipa) tenuisima

Fountain Grass – Pennisetum setaceum

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But most have modified roots & stems

that help them to thrive

Runners (stolons): A well known example of that would be crabgrass. It spreads with creeping stems that grow along the ground. Buds along the runners produce plantlets that root and spread very quickly

Roots or Rhizomes: Quackgrass would fall into this category. It has tough, white rhizomes that look like roots and are very sharp. Weeds that spread by roots or rhizomes can regrow after being cut back. Even chopped up pieces of root or rhizome may regrow.

Bulbs and bulbils: An example of this is a spiky grass called nutsedge. It has tubers or little bulbs that break off when you pull the grass therefore never eliminating the plant. They can pop up over night (again and again and again...!).

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Weeding Perennial Weeds

If you catch them young, perennial weeds can usually be pulled out of the ground easily.

Once established, they can be next to impossible to get rid of, as anyone who has battled Bermuda grass or yellow nutsedge in flower beds will attest.

With perennials, it is essential to get all of the plant out of the ground. When perennial weeds are tender seedlings, they can usually be pulled up by hand with ease, especially when the soil is moist. But the more time you allow these weeds to take hold, the harder they are to eradicate. The least bit of Bermuda grass rhizome left behind can sprout into a new plant.

The best time to weed is shortly after a rain or an irrigation cycle. Hand-pulling is the quickest method. If the weeds don't yield easily or if they detach from the roots when you pull, switch to a trowel or dandelion weeder and dig or pry them out.

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http://www.clintsdandydigger.com/

‘Weed Twister vs. Tree of Heaven

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Special management strategies for perennials

Exhaust the roots by continual cutting/hoeing

Remove roots/rhizomes or other reproductive organs from the soil

http://www.moberlymo.org/index.aspx?NID=232

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Hoeing and tilling are not good choices for removing perennial weeds.

Hand weeding will work if you are very thorough about getting the whole plant and root system.

Sometimes herbicides are the only solution for eradicating tough perennial weeds like poison ivy, ground ivy and brambles.

http://pirateneo1.blogspot.com/2009/03/back-soon.html

Burmuda Buttercup : Oxalis pes-caprae

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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

Control Methods: Dig out small plants before they set

seed.

Water deeply but infrequently

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Yellow (Creeping) Woodsorrel - Oxalis corniculata

Control Methods:

For chemical control, use a pre-emergence herbicide containing oryzalin or pendimethalin to prevent seeds from germinating and becoming established. Spot-treat oxalis in garden areas with glyphosate, taking care to avoid contact with desirable plants

http://www.ipm.ucdavis.edu/PMG/WEEDS/creeping_woodsorrel.html

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Integrated Pest Management (IPM)

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 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. 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 agent feeds and develops only on the intended weed species. Therefore, the risk to other plants and organisms in the ecosystem is minimal.

Examples: Large herbivores: sheep, goats Weed-specific pests (insects)

Example: releasing weevils that eat the seed of musk thistle; Releasing an insect whose larvae eat the roots of the weed. -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.

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

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Integrated Pest Management (IPM)

Chemical controls

Non-biologics Vinegar mixed with a little dish soap

Non-selective – don’t get it on things you want

Works best on young weeds

Salt – best for weeds in pavement

Biologics Example: AAL-Toxin (isolated from

the pathogenic fungi, Alternaria a lternata f. sp. lycopersici ) - Highly susceptible species include such important agricultural weeds as black nightshade

http://www.housenumbers.ca/weeds.html

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Control methods: ‘Safe Organic’ pre-

emergents with corn gluten meal

‘Safer ‘Concern’ - Contains corn gluten meal (84%) and sulfate (16%) Application Recommendations:Apply 10-20 lbs. per 1000

square feet in the Spring & Fall for pre-emergent protection. Weed Prevention Plus is granulated and easy to apply with a spreader or you can apply with the 5 lb. shaker bag to small garden areas. Homogenous pellet provides 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, dandelions, crabgrass and many other common weeds. Proper application provides up to 90% effective weed control in the first year for dandelions and crabgrass. Safe for children, pets and wildlife immediately after application. Can be applied at any time without burning. Water thoroughly after application then allow to dry for 2-3 days.

http://www.organic-gardening-shop.com/Agorganics/Product_Details.aspx?ProductID=120

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Some pesticide definitions

Preemergence Herbicides

Preemergence herbicides affect germinating seeds.

To be effective, the herbicide should be applied two to three weeks before weed seeds germinate.

Consequently, preemergence herbicides are most effective against annual weeds.

Postemergence Herbicides

Postemergence herbicides are used to kill weeds after the weed plants are up and growing.

To be effective, most postemergence herbicides must be absorbed through the leaves; consequently, liquid sprays generally work better than dry, granular materials.

Postemergence herbicides are most effectively applied when weeds are young and growing vigorously.

For some weeds, repeated application at 20–30 day intervals may be required for control.

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Some pesticide definitions

Selective postemergence herbicides are usually used to control annual,

biennial, and perennial broad-leaved weeds because they will kill many broadleaf plants without damaging grass plants.

There are also selective herbicides that kill only grasses

Nonselective postemergence herbicides kill all plants, both desirable and

undesirable. These herbicides can be used to spot

treat perennial grassy weeds that are not affected by selective herbicides.

To spot treat an area, thoroughly wet the weed foliage with herbicide solution.

http://www.dgsgardening.btinternet.co.uk/weedremoval.htm

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How do herbicides work

Pre-emergent

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

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Herbicides: pre-emergent

Last 6-12 months

http://www.ctmpest.com/weedPreventionAndControl.htm

http://www.viewpoints.com/Preen-Garden-Weed-Preventer-review-166f1

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Herbicides – post-emergent

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Yellow nutsedge - Cyperus esculentus

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

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Bindweed - Convolvulus arvensis

Characteristics: Also called wild morning glory, bindweed

grows in open areas usually in loam to clay soils

Growth form: perennial vine from deep root

How it spreads: Bindweed is deep rooted, so pulling

usually doesn't eradicate it ― the stems break off, but the weed returns from the roots.

Control Methods: 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!

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Bindweed - Convolvulus arvensis

Control Methods: For chemical control, you can use a pre-

emergence herbicide containing trifluralin around ornamentals. In midsummer, when bindweed is at the height of its growth season but has not yet set seed, spot-treat isolated patches with glyphosate, taking care to avoid contact with desirable plants. If the weed is twined around desirable plants, detach it before treating. Repeated applications are usually needed to destroy the root system.

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Bermuda Grass - Cynodon dactylon

Characteristics:

A fine-textured and fast-growing perennial, frequently planted as a lawn

Growth form: perennial grass (summer)

How it spreads: spreads by underground stems (rhizomes), above ground runners (stolons), and seed.

Control Methods:

If you have a Bermuda grass lawn, use deep barriers or edging to prevent it from advancing into other parts of the garden.

http://www.aragriculture.org/horticulture/ornamentals/weed_id/bermudagrass.htm

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Bermuda Grass - Cynodon dactylon

Control Methods:

Dig up stray clumps before they form sod, being sure to remove all the underground stems; any left behind can start new shoots. Repeated pulling and digging are generally necessary to stop this weed; mulches will slow it down, but it eventually grows through most of them.

For chemical control, you can use a selective herbicide containing fluazifop-butyl or sethoxydim, which can be sprayed over some ornamentals. Spot-treat actively growing Bermuda grass with glyphosate, taking care not to get the chemical on desirable plants.

http://www.ipm.ucdavis.edu/PMG/WEEDS/bermudagrass.html

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Other weedy grasses that spread via

seed and rhizomes

Quack grass - Elytrigia repens Panic Veldt Grass - Ehrharta erecta Kikuyugrass -

Pennisetum clandestinum

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Safety precautions when using herbicides

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, separate room, building or covered area

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Most herbicides become less effective when a plant is under stress. Along with crops, most weeds are also experiencing water stress under current conditions. Therefore, you may have to wait until the soil is fairly moist before applying any systemic herbicides (e.g., Roundup) to manage weeds.

Most systemic herbicides perform better under conditions that are ideal for weed growth. When the plants are free of stress, herbicides are absorbed faster and move better within the plant system, providing more efficient kill.

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Fall is a good time to apply systemic herbicides to manage perennial weeds. These weeds have perennating organs like rhizomes and stolons that help them persist year after year. Development of these organs usually occurs during the early fall. During a drought, it is possible that drought tolerant 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 absorbed and moved within the plant tissues). A non-selective systemic herbicide like glyphosate could be applied as a spot application. Grass killers (graminicides) like sethoxydim, clethodim or fluazifop may also be applied during fall to manage perennial grasses.

The main key to control of perennial weeds is application of glyphosate, 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 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 entire plant. The best opportunity for making this type of application is during the late-summer through fall after wheat harvest when plants have grown undisturbed for several months.

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Potential problems with use of herbicides

Cost

Herbicide-resistant weeds. The evolution of "superweeds" capable of resisting herbicides

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Summary: Identifying a weed will allow you

to choose the best strategy to prevent its

spread

Annual weeds – reproductive strategy: seeds Key – prevent seed production

Biennial/non-spreading weeds – reproductive strategy: seeds Removal (mechanical best) – hopefully when young (year 1) Prevent seed production – year 2

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

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Advice from pros: The ABC’s of Weeding

Learn how the weeds spread (root system or seed dispersal) to understand when and how to handle them.

Keep cultivation/tilling to a minimum

Get the weeds early before they flower and go to seed.

Get ‘em while they’re small.

Frequent, short weeding sessions are the best way to stay on top of weeds. Not only does this eliminate a long, tiring weeding session, it also lets you dispatch weeds while they’re still small and easy to eliminate.

Weed wet. Weeding goes faster and easier when the soil is moist than when the soil is dry

http://walkinggodsway.blogspot.com/2008/06/taught-

through-image-today.html

Repetition is the key to combating persistent weeds. Even tough weeds such as bindweed and kikuyu grass can be brought under control with careful and fastidious weeding practices.

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What is a noxious weed?

Invasive alien plant: an invasive unwanted non-native plant According to The Flora of North

America, the most comprehensive reference on this continent's plants, one-fifth to one-third of all species growing north of Mexico have come from other continents.

Noxious weed: any species of plant which is, or is likely to be, detrimental or destructive and difficult to control or eradicate

We are located in the Los Angeles Weed Management area – report noxious weed infestations to them

http://www.co.chelan.wa.us/nw/nw_weed_photos.htm

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Comparison of common weedy plants and invasive plants.

Agricultural or garden weeds Invasive plants

Introduction Usually accidental by people,

animals, equipment, or seed

contamination.

Can be accidental, but more often

the original intention was for

ornamental or aquarium use, or for

forage, food, fiber, medicinal, or soil

stabilization purposes.

Disturbance Require human disturbance to

establish and persist.

Benefit from human disturbance, but

disturbance not required.

Persistence Will not persist without human

disturbance, usually soil tillage or

irrigation.

Once introduced, plants survive and

spread on their own without further

human assistance.

Life form Primarily terrestrial annuals or

herbaceous perennial species.

All growth forms, including aquatic,

climbing vines, parasitic,

herbaceous, or woody plants. Can

have annual, biennial, or perennial

life cycles.

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74139.html

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In natural areas (and in your garden ecosystem), noxious weeds impact native ecosystems by:

Reducing biodiversity

Altering hydrologic (water) & soil conditions

Altering fire intensity and frequency

Modifying successional pathways

Competing for pollinators

Displacing rare plant species

Replacing complex communities with simple communities

http://faculty.jsd.claremont.edu/dthomson/studentres.htm

http://www.nps.gov/hafo/naturescience/grasses.htm

Cheat Grass – Bromus tectorum

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Characteristics of invasive plants: general

Fast, aggressive growth that robs soil, water and nutrients from desirable plants nearby.

Quick adaptation to the existing environment.

Ability to thrive in disturbed areas (wet or dry) and poor soil.

Resistance to heat and drought.

Deep, strong roots making them difficult to eradicate.

Lack of natural pest or predator. Invasive species seldom show signs of disease or pest damage.

Some invasive species are able to produce toxins that inhibit competitor's growth.

Coast Acacia – Acacia cyclops

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What you can do about invasive weedy

plants in S. CA

1. Know what species are a problem in your area

2. Get rid of these plants in your yard

3. ‘Don’t Plant a Pest’ 4. Report infestations 5. Lobby to get weedy

pest plants out of the horticultural trade

http://resistancestudies.org/?cat=3

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Where to learn more about invasive

plants…

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Don’t Plant a Pest Iceplant/hottentot fig (Carpobrotus edulis)

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)

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 http://www.cal-ipc.org/landscaping/dpp/socal.php

Acacia

Myoporum

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I thought that was a native plant…

Some native plants can ‘take over’ and become weedy or invasive: ‘groundcover’ natives that

spread via rhizomes [Woodmints] or stolons [native strawberries]

Clonal species [Narrow-leaf Willow; some of the shrubby native mallows]

Plants that grow very fast [Calystegia]

Plants that reseed very well in your yard [grasses; some wildflowers]

Know the characteristics; plant where you take advantage of these characteristics – e.g., where you want them to take over

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Climate change & invasive plants

Gardeners may also have to cope with a new cast of characters. Some researchers are trying to identify exotic species with weed potential before they jump the garden fence - plants with windblown or bird-dispersed seeds, species that reproduce vegetatively through runners, generalists that thrive in a variety of habitats - and working with growers and nursery folk to make sure new invasives don't get into the horticultural trade.

Climate change is a moving target, and some effects could turn out to be stronger than the models account for. There's also no foolproof way to identify which plants will become invasives. But with weeds moving both in from wildlands and out into them, it's safe to say that weed control will still be on every thoughtful gardener's agenda.

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“When you want to shift your ch’i (energy), go to your garden and start pulling weeds.”