1/7/2013
1
© Project SOUND
Out of the Wilds and Into Your Garden
Gardening with Western L.A. County Native Plants Project SOUND - 2009
© Project SOUND
Weeds & More
Weeds
C.M. Vadheim and T. Drake
CSUDH & Madrona Marsh Preserve
Madrona Marsh Preserve
September 5th 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/ © Project SOUND
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/
1/7/2013
2
© Project SOUND
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
© Project SOUND
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)
© Project SOUND
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
© Project SOUND
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!
1/7/2013
3
© Project SOUND
The more you know about your garden’s own weeds, the better you
will be able to deal with them
© Project SOUND
In the garden (and in the operating room), first do no harm
Your plan to combat weeds should be reasonable and
environmentally friendly
© Project SOUND
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)
© Project SOUND
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.
1/7/2013
4
© Project SOUND
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.
© Project SOUND
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).
© Project SOUND
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
© Project SOUND
If you can, do a little bit – but do it consistently
Weeding just 15-30 minutes a day is often all that’s needed
1/7/2013
5
© Project SOUND
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 © Project SOUND
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
© Project SOUND
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 © Project SOUND
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)
1/7/2013
6
© Project SOUND
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
© Project SOUND
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
© Project SOUND
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 © Project SOUND
Great resources on-line & in books
1/7/2013
7
© Project SOUND
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 © Project SOUND
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
© Project SOUND
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
© Project SOUND
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/
1/7/2013
8
© Project SOUND
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
© Project SOUND
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
© Project SOUND
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 © Project SOUND
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
1/7/2013
9
© Project SOUND
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
© Project SOUND
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
© Project SOUND
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 © Project SOUND
Key preventive method: blocking sunlight
so light-requiring seeds can’t germinate
Mulches Organic
Inorganic
‘Weed block’ methods
Planting natives that will create shade
1/7/2013
10
© Project SOUND
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 © Project SOUND
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
© Project SOUND
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 © Project SOUND
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
1/7/2013
11
© Project SOUND
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
© Project SOUND
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
© Project SOUND
IPM plan changes through the life of a garden/bed
Pre-planting: Prevention/removal
Pre-planting: Prevention/practices
Years 1-2: Monitoring & Removal
© Project SOUND
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
1/7/2013
12
© Project SOUND
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 © Project SOUND
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
© Project SOUND
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
© Project SOUND
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
1/7/2013
13
© Project SOUND
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
© Project SOUND
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
© Project SOUND
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
© Project SOUND
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
1/7/2013
14
© Project SOUND
Control methods: mechanical
http://landscaping.about.com/od/weedsdiseases/ss/weed_fabrics_3.htm © Project SOUND
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
© Project SOUND
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.
© Project SOUND
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
1/7/2013
15
© Project SOUND
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
© Project SOUND
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
© Project SOUND
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
© Project SOUND
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
1/7/2013
16
© Project SOUND
What the pro’s like….
Asparagus knife Hori-hori knife Fiskars ‘Big Grip Knife’
(~$10)
http://www.fine-tools.com/garten.htm
© Project SOUND
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
© Project SOUND
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/
© Project SOUND
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
1/7/2013
17
© Project SOUND
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...!).
© Project SOUND
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.
© Project SOUND
http://www.clintsdandydigger.com/
‘Weed Twister vs. Tree of Heaven
© Project SOUND
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
1/7/2013
18
© Project SOUND
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
© Project SOUND
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
© Project SOUND
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
© Project SOUND
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
1/7/2013
19
© Project SOUND
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
© Project SOUND
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
© Project SOUND
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. © Project SOUND
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
1/7/2013
20
© Project SOUND
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
© Project SOUND
Herbicides: pre-emergent
Last 6-12 months
http://www.ctmpest.com/weedPreventionAndControl.htm
http://www.viewpoints.com/Preen-Garden-Weed-Preventer-review-166f1
© Project SOUND
Herbicides – post-emergent
© Project SOUND
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
1/7/2013
21
© Project SOUND
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!
© Project SOUND
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.
© Project SOUND
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
© Project SOUND
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
1/7/2013
22
© Project SOUND
Other weedy grasses that spread via
seed and rhizomes
Quack grass - Elytrigia repens Panic Veldt Grass - Ehrharta erecta Kikuyugrass -
Pennisetum clandestinum
© Project SOUND
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
© Project SOUND
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.
© Project SOUND
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.
1/7/2013
23
© Project SOUND
Potential problems with use of herbicides
Cost
Herbicide-resistant weeds. The evolution of "superweeds" capable of resisting herbicides
© Project SOUND
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
© Project SOUND
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.
© Project SOUND
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
1/7/2013
24
© Project SOUND
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 © Project SOUND
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
© Project SOUND
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
© Project SOUND
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
1/7/2013
25
© Project SOUND
Where to learn more about invasive
plants…
© Project SOUND
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
© Project SOUND
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
© Project SOUND
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.
1/7/2013
26
© Project SOUND
“When you want to shift your ch’i (energy), go to your garden and start pulling weeds.”