Garden Weeds - notes

1/7/2013

Out of the Wilds and Into Your Garden

Weeds & More
Weeds

C.M. Vadheim and T. Drake
CSUDH & Madrona Marsh Preserve

Madrona Marsh Preserve
Gardening with Western L.A. County Native Plants September 5th 2009
Project SOUND - 2009
© Project SOUND © Project SOUND

Does this look like your garden? What is a weed? (definition)
 Weed: any plant that is growing
at a site where it is not wanted

You’re not alone – weeds
are a perennial concern in
S. California gardens!

http://www.progardenbiz.com/wp/weeds-who-they-are-and-what-they-tell-us/
http://www.entrepreneurs-journey.com/824/how-i-made-six-figures-in-one-day/ © Project SOUND © Project SOUND

1

1/7/2013

Why control weeds? (it’s a war out there!) Weeds are particularly challenging in W. L.A. County

 Weeds compete with desirable  No killing frosts or smothering
plants for: snow; weeds that are annuals in
 Light many climates are perennial in
 Water ours
 Nutrients
 No killing high temperatures
 Space
 Weeds also provide hiding  People water a lot (up to now)
places for insects and serve as a  Lots of weedy plants to spread
source of plant diseases. their seeds/invade via roots
 Weeds can kill a gardener’s http://acwm.co.la.ca.us//scripts/wma_4.htm#F  Use of ‘mow & blow’ gardeners –
enthusiasm, which can cause weeds hitch-hike between
http://www.nature.org/wherewework/northamerica/states/hawaii/ them to abandon the garden; Castor Bean ( Ricinus communis) gardens
Game ends – weeds win
projectprofiles/art26290.html


Where do alien weeds come from? Weeds tell a story….
 Many of California’s noxious
and invasive weeds came from
regions with comparable  Type of soil – some prefer
climates in the Mediterranean certain soil characteristics
region, Australia, S. Africa
 Available light
http://www.grabovrat.com/mapsViews/mapsViews80.html  Others, including many garden  Soil nutrient levels (low or
Mediterranean Climate Zones weeds come from nearly all high)
parts of the globe, including
particularly western and  Watering practices
central Asia, Russia & Europe
 Cultivation practices – how
 They were introduced through much the soil is disturbed
human activity, both To know a weed is to
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pni74139-2.html accidentally and intentionally, learn about your garden –  And many other things
including by gardeners. and to understand how to
Percentage of invasive plants accidentally or combat it!
intentionally introduced to California. © Project SOUND © Project SOUND

2

1/7/2013

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

The more you know about your garden’s own weeds, the better you Your plan to combat weeds should be reasonable and
will be able to deal with them environmentally friendly

The IPM Pyramid – ‘first do no harm’
Integrated Pest Management (IPM)  Use the least invasive – and
often most effective - means
first:
 "Optimum combination of control methods  Prevention – cultural
practices
including biological, cultural, mechanical,  Mechanical Controls
 Naturally occurring
physical and/or chemical controls to reduce biological controls (native)
pest populations to an economical  Consider using non-native
acceptable level with as few harmful biological controls
(herbivores; diseases)
effects as possible on the environment and http://www.team.ars.usda.gov/ipm.html
 Use chemical controls
nontarget organisms." sparingly, as a last resort:
Non-native and chemical controls may
 Naturally occurring elements
R.L. Hix,CA Agric. Magazine, 55:4 (2001) have the important drawback of non-  Biologics – chemicals made
specificity – they kill the good species by plants that are toxic to
weeds
along with the bad.
 Non-biologic herbicides

3

1/7/2013

An IPM system is designed around six
basic components An IPM system is designed around six
basic components
1. Set Action Thresholds
 Before taking any pest control action, IPM first sets an action
threshold, a point at which pest populations or environmental 4. Mechanical controls: Should a pest reach an unacceptable level,
conditions indicate that pest control action must be taken. The level mechanical methods are the first options to consider. They
at which pests will either become an economic threat is critical to include simple hand-weeding, erecting weed barriers, and tillage
guide future pest control decisions. to disrupt breeding.
2. Monitor and Identify Pests
5. Biological controls: Natural biological processes and materials can
 Not all insects, weeds, and other living organisms require control. provide control, with minimal environmental impact, and often at
IPM programs work to monitor for pests and identify them low cost. The main focus here is on promoting beneficial
accurately, so that appropriate control decisions can be made in herbivores that eat target pests. Use of plant pathogens – ones
conjunction with action thresholds. This monitoring and specific to the weeds of interest - also fits in this category.
identification removes the possibility that pesticides will be used
when they are not really needed or that the wrong kind of pesticide
will be used. 6. Chemical controls: Synthetic pesticides are generally only used
as required and often only at specific times in a pests life cycle.
3. Preventive Cultural Practices Many of the newer pesticide groups are derived from plants or
 As a first line of pest control, IPM programs work to manage the naturally occurring substances (e.g.: allelopathic analogues), and
crop, lawn, or indoor space to prevent pests from becoming a further 'biology-based' or 'ecological' techniques are under
threat. These control methods can be very effective and cost- evaluation (particularly for agriculture, forestry applications).
efficient and present little to no risk to people or the environment.

Integrated Pest Management (IPM) If you can, do a little bit – but do it consistently
applies to weeds as well as other pests

 Set Action Thresholds
 Does your entire yard need to be
weed free? Choose an area and
focus on it.
 Prioritize weeds by invasiveness
 When to take action against
specific weeds
 In general, a smaller weed is easier to
http://www.statuaryplace.com/store/index.php?main_
page=index&cPath=46
remove than a larger one
 In general, you want to remove a weed
before it flowers & sets seed Weeding just 15-30 minutes a day is often all that’s needed

4

1/7/2013

Integrated Pest Management (IPM) Climate change: long periods of hot
Monitor and Identify Weeds weather during winter rains
 Get to know the ‘weed seasons’ of your
yard:
 Cool-season weeds sprout any time from
fall through spring. They flower in late
spring/early summer. The plant may
disappear during the hot dry summer, but
you’ll see even more of germinating
seedlings the following fall.
http://www.dynamiteexterminators.com/WeedFacts.html

Cool season weed  Examples: Annual Bluegrass, Bermuda
Annual Bluegrass – Poa annua Buttercup; Mustards; Clovers; Cheeseweed
 Warm-season weeds tend to start growing
in the spring and hang around all through
the growing season.
 Examples: Crabgrass; Bermuda Grass; Kikuyu
Grass; Fountain Grass; Spotted Spurge;
Bindweed; Nutsedge;

 Any season – some species grow all year
long in our climate
Favors growth of many weeds: jump-start on growth season
Warm season weed  Examples: Creeping Woodsorrel (Oxalis) ;
Crabgrass – Digitaria species Example: Panic Veldt Grass - Ehrharta erecta

Integrated Pest Management (IPM)
Each garden is unique: garden weeds in context
Monitor and Identify Weeds
 Soil (including previous amendments)
 Get to know the geography of  Light & water
your garden’s weeds  Gardening practices: tilling, raking,
mulches, ‘top soil’, hired gardener’s
 Areas prone to weeds require practices
special monitoring & early
intervention  The age of the garden (or part of the
garden)
 Discovering geographic patterns
 Previous (and current) plants
may suggest changes in gardening
 Weeds that hitch-hike in with purchased
practices – decreasing water to the plants
area; increased hand-weeding  Invasive garden plants [ivy; bamboo;
frequency; etc. dichondra; etc]
 Know that wildlife (birds, etc) will Dichondra  What’s growing nearby:
bring seed into your yard. Be extra Dichondra micrantha  Birds bring seeds; seeds blow
vigilant in areas where they eat, (Dichondra repens)  Weeds grow into the yard
Oxalis/ Creeping Woodsorrel
perch etc.
Oxalis corniculata
We will introduce you to some general principles, strategies and tools
© Project SOUND that you can apply to your own situation © Project SOUND

5

1/7/2013

Garden weeds may vary widely from year to year… The Weed IPM plan for your garden – a
work in progress
 Example: Shepherd’s Purse
(Capsella bursa-pastoris)
 Requires observation &
 Why? knowledge – specific for
 Conditions are right for your garden
germination of dormant seeds;
temperature; rainfall  Will vary somewhat with:
 Seeds survive up to 35 years in  Yearly weather conditions
undisturbed soils  Maturity of plants
 When conditions are right – they
http://www.hoodcountymastergardeners.org/Demo_2006/Demo_Construction.html

are ready
 New plants, and other
changes to the garden
 New seeds may have been
brought in by gardening practices  Will be modified based on
 New seeds may have come in your previous experiences
through natural means; wind,
birds, etc.  Suggestion: keep a garden
http://www.plant-identification.co.uk/skye/cruciferae/capsella-bursa-pastoris.htm
notebook/journal

Identifying weeds Great resources on-line & in books
 Proper weed identification may be your
hardest task.
 Flowering and growing patterns are of great
importance as most weeds are classified as
either annual, biennial, or perennial.
 The color, shape, and placement of the flower
on the weed will also aid you in identifying the
weed.
http://www.hear.org/starr/plants/images/image/?q=061205-1921
 Take pictures of the weeds – or collect and
Kikuyu grass press them - as you find them; makes
Pennisetum clandestinum identifying and recognizing weeds much
easier.
 Try to find them on-line, in books or have
them identified by an expert (County
agriculture extension; local weed control
district).
 If “new” or unfamiliar weeds appear, have
them identified quickly and take appropriate
http://www.tropicalgrasslands.asn.au/pastures/kikuyu.htm
control measures if necessary © Project SOUND © Project SOUND

6

1/7/2013

Identifying weeds is key to your weed strategy Integrated Pest Management (IPM)
Preventive Cultural Practices
 Knowing the ID of a weed will
tell you:  The first line of defense against all weeds is
 Growth pattern – annual or good prevention
perennial weed
 General goals:
 Cool/warm season weed – when
http://www.earthlygarden.com/category/lawnmower-maintenance/
to look for it  Prevent the introduction of weeds into the garden

 How it likely enters your garden  Prevent the spread of weeds in the garden
– suggests ways to prevent this  Promote the health & vigor of desired species
 Useful mechanical/physical
 ‘An once of prevention is worth a pound of cure’
controls
– simple preventive practices can save you
 Chemical controls (if needed) serious gardening headaches
Kikuyu grass is used for lawns © Project SOUND © Project SOUND

Common Purslane - Portulaca oleracea Prevention/Cultural Practices – avoidance/
 Characteristics: prevention is key
 Succulent foliage (healthy edible;  Avoid introducing new
probably should be grown as a garden weeds into the garden:
vegetable)
 Grows in moist areas (usually)  Use only weed-free mulch,
 Summer (warm season); origin - Asia topsoil, other amendments (if
any); beware of ‘free’ material
 Growth form: herbaceous annual unless you know it will not
contain weeds/weed seeds
 How it spreads: seeds (> 50,000 per plant;
http://www.ppws.vt.edu/scott/weed_id/porol.htm

stem pieces  Check new plants to be sure
that weeds are not
 Control Methods: ‘hitchhiking’ in the pots
 Solarization for pre-planting removal.  Be sure to not bring weed
 Mulch & dry conditions usually prevent it seeds into garden on your
from establishing clothes, shoes, etc.
 Easy to pull or hoe, but pieces of stem
can re-root readily, so be sure to remove http://asimpleyarn.net/category/garden-on-tuesday/

http://commons.wikimedia.org/wiki/File:Portulaca_oleracea_stems.jpg them from the garden.

7

1/7/2013

Cultural practices: just good old garden Cultural practices: good garden management
management practices  Keep garden plants healthy; help
them to out-compete the weeds
 Sanitation
 Plant native plants densely
 Clean equipment (including
lawnmowers) to prevent spread of
enough to crowd out weeds
weed seeds/cuttings
 Choose native plants that:
 Weed Disposal:  Are vigorous growers – will out-
 Annual weeds can be composted if compete the weeds
they are not in seed.
 Will prevent weeds from growing
 Place perennial weeds in a garbage by:
bag, solarize (leave bag in sun) &
http://www.norcalblogs.com/sustainable/2008/10/compost_
clueless.html

dispose of them in green waste.  Providing too much shade
Note: a ‘hot’ compost bin will kill  Producing allelopathic chemicals that
some – but not all – weed seeds,  If any weed is a big problem in your
either inhibit weed seed germination
garden, think twice before putting it
so be cautious
or weed growth: examples: Salvias?,
in the compost pile. Chamise, Manzanitas, CA Walnut,
Purple Sage – Salvia leucophylla probably other CSS species

Integrated Pest Management (IPM) Fortunately, weeds need water to germinate
Physical Prevention – 2nd line of prevention and grow
 Weeds have growth requirements -  Water-wise gardening methods
like any other plant: will limit some weeds, simply by
 Water decreasing available water
 Particularly helpful for shallow-
 Correct amount of light rooted weeds
 Correct temperature  Also useful for ‘weeds of wet
places’ – will not survive in dry
 Appropriate nutrients soil
 Prevent seed germination & seedling  Use target watering methods –
growth by limiting the weed’s access water only the plants you want
to ‘growth requirements’ (drip; hose)

 Remember: limit any one of these  Be patient – first couple of
and you’ll significantly decrease the years, when you need to water
ability of a weed to take over your shrubs more, are the worst
garden Broadleaf Plantain - Plantago major
Black Nightshade - Solanum nigrum

8

1/7/2013

Broadleaf Plantain – Plantago major Before planting a new area…prevention
 Characteristics:
almost always better than control
 Large leaves from basal rosette; originally
brought from Europe as medicinal plant  Kill weed plants & seeds
 Usually in damp area of garden  Solarization
 Chemical methods
 Growth form: herbaceous perennial
 How it spreads: seed  Turn the soil as little as
possible – avoid bringing up
 Control Methods:
buried weed seeds
 Crowd out; needs bare soil to germinate, grow
 Decrease water; aerating the lawn will also  Control weeds before
help. installation – always less work
 Dig out before they set seed. Be sure to
in the long run
http://www.wildflowers-and-

remove as much of the roots as possible - can
weeds.com/Plant_Families/Plantaginaceae.htm

 Be patient – the more
regrow from any pieces of the fibrous weeds/seeds are removed
You can use your knowledge of rootstalk that remain in the soil. before installation, the fewer
a weed’s growth requirements
to save time and effort  Chemical control -spot-treat with glyphosate http://earthlandscapes.blogspot.com/2008/02/how-to-choose-best-lawn-grass-2.html you’ll have to pull later
(Roundup), taking care not to get the chemical
Bermuda Grass
on desirable plants. Cynodon dactylon

Understanding seeds: what seeds need to
Key preventive method: blocking sunlight
germinate
so light-requiring seeds can’t germinate
 Water – need to ‘re-hydrate’ before
seedling can start to grow
 Mulches
 Light (small seeds, including many
weeds) or dark (larger seeds)
 Organic
 Inorganic
Virgin’s Bower - Clematis ligusticifolia  Correct temperature; may be warm
Native plant – requires cold treatment or cool – and may be a rather narrow  ‘Weed block’ methods
range. In general, weeds tend to
have larger ranges, but many are  Planting natives that will
‘warm season’ or ‘cool season’ weeds
create shade
 Other factors (heat; smoke; cold
pre-treatment, etc): in general,
Oxalis/ Creeping Woodsorrel
weed seeds have few of these – it’s
Oxalis corniculata one of the reasons they are so
Weed – no special requirements successful
http://www.ars-grin.gov/npgs/images/sbml/?C=M%3BO=A

9

1/7/2013

Why barrier methods work: Plastic weed barrier cloth (weed block) –
several effects is it good for native plant gardens?
 Block light, preventing seed Arguments for Arguments against
germination
 Doesn’t stop all weeds from growing
 Physically prevent seedling  Stop some weeds seeds  Weeds grow through the holes cut for
growth from germinating; blocks planting
 Reduce soil temperature – light & forms physical  Weeds grow through/on top of the
particularly in spring – delay barrier barrier cloth
emergence  Relatively easy to install  Cloth gets clogged over time – becomes
a water barrier
 Increase soil moisture below
the barrier – too much for  Can promote stem & root fungal disease
some species (seeds & in trees & shrubs; interferes with
seedlings rot) proper drainage
 Decrease moisture above the  Doesn’t allow groundcover plants to
barrier – too dry for root – or for successful re-seeding
germination
 Hard to keep from looking unsightly-
 Chemical compounds released even under mulch
from barriers/ mulch may
inhibit germination and/or kill  Can’t be used well on slopes or other
seedlings uneven terrain
http://landscaping.about.com/od/weedsdiseases/ss/weed_fabrics_6.htm
© Project SOUND http://homeideas.howstuffworks.com/weeds-and-invasive-plants/weed-barrier-basics.htm © Project SOUND

Physical barriers Eco-friendly ‘weed
have their place block’ choices
 Weedblock (plastic or other)
 Newspaper (use a good
 Under pathways
 Under patios, sitting areas thickness to block light)
(hardscaped areas)
 Cardboard
http://blueplanetgardening.com/sm-push-mulch-away.jpg
http://www.ndmnaturescapes.com/freshplanting.htm
 Other areas where planting is
not an option
 Degradable weed block
 Other physical barriers (e.g.,
mowing strip, heavy metal or materials – most are
wood strip set on edge) at shrub paper-based
bed/turf interface to prevent
turf and turf weeds from
encroaching into planted beds

You may also choose more eco-friendly barriers © Project SOUND
‘Garden Trail’ weed block © Project SOUND

10

1/7/2013

What kinds of seeds Mulch – the best surface physical barrier
are susceptible to for native plant gardens
‘dark inhibition’?
 Kind of mulch
 annual species that are small-  Should be appropriate for the native
seeded and have a light plants you’ve planted
requirement for germination  Organic (bark, etc) for most local
such as common lambsquarters shrubs/trees
‘Garden Trail’ weed block
and pigweeds are sensitive to  Inorganic for Coastal Prairie
surface barriers (wildflowers) and desert plants
 large-seeded annuals and  Must be course enough texture to
perennial weeds are relatively allow the mulch surface to dry out
insensitive to the darkness;
however barriers/mulches still  Depth of mulch layer
provide mechanical barriers to
seedling growth.  Must be deep enough to prevent
Lesson: geography of weeds light from reaching the seeds
suggests that mulch layer may be beneath it.
too thin at the edge

IPM plan changes through the life of a garden/bed
Knowing the life cycle of weeds is key to your plan
 Knowing the ID of a weed will
tell you:
 Growth pattern/life cycle –
annual, biennial or perennial
weed
 Cool/warm season weed – when
to look for it
Pre-planting: Prevention/removal Annual weed – Gnaphaleum sp.
 How it likely enters your garden
– suggests ways to prevent this
 How it spreads
 Useful mechanical/physical
controls
 Chemical controls (if needed)
Years 1-2: Monitoring & Removal
Perennial weed - Oxalis pes-caprae
Pre-planting: Prevention/practices

11

1/7/2013

Annual, Biennial & Perennial Weeds Annual weeds  Spread by seed. They may self-seed or
they may be brought into the garden by
wind, water, birds, animals or people.
Short-lived (fixed)
Spreading  The most important way combat annual
Character Annuals perennials or
perennials weeds to prevent more seeds from
biennials developing. Annual weeds are
Vegetative phenomenally prodigious seed producers.
< 1 year 2 to a few years Long, indefinite
lifespan  A single crabgrass plant, for example,
Vegetative can produce 100,000 seeds
No Accidental Yes
reproduction  If you don't get rid of these intruders
before they develop viable seeds, the
Seed longevity Years to decades Years to decades A few years number of weed plants will increase
Energy allocated every year,
to seed High Medium high Low  Examples of annual weeds include:
production bindweed, chickweed, crab grass,
knotweed, lambs-quarters, mallow,
Establishment Seeds Seeds Mainly vegetative pigweed, purslane, speedwell, spurge and
Usual means of In soil, manure, Soil, wind, feces, yellow oxalis
In soil
dispersal equipment, wind crop seed  Your strategy: kill before they flower
Lambsquarters, Quackgrass, Annual Sowthistle & set seed
Examples Dandelion
Annual Bluegrass
http://www.css.cornell.edu/weedeco/WeedDatabase/index2.html bindweed Sonchus oleraceus

Annual weeds, ancient wisdom Puncture vine - Tribulus terrestris
 Characteristics:
 Sharp, thorny burs
 Grows in dry areas of garden
http://www.backsavergrip.com/photos.htm
 Growth form: herbaceous annual

 How it spreads: seed

 Control Methods:
 Prevent introduction: sanitation

http://www.ppws.vt.edu/scott/weed_id/trbte.htm  Hoe or dig plants before they can set seed;
cut below the crown to prevent regrowth.
http://www.english.illinois.edu/maps/poets/a_f/erdrich/boarding/gallery.htm
 Chemical control: pre-emergence herbicides
containing trifluralin or pendimethalin may
 Getting weeds out of the garden at the start of the season, be used on some lawn grasses and
when they're most vulnerable, is a smart strategy: it is easiest ornamentals. For post-emergence control in
then & it keeps annual weeds from forming seed heads lawns, use a selective herbicide containing
MCPA, MCPP, and dicamba.

12

1/7/2013

Vigilance is the key Crabgrass - Digitaria species
 The only way to control annual
weeds is to get rid of them before  Characteristics:
they go to seed. Luckily annual  Thrives in hot moist areas – lawns,
weeds are very often shallow flower gardens
rooted and can be easily hand  Shallow-rooted
pulled or cut off with a hoe.
 Growth form: annual grass
 Hopefully you will see less and less
annual weeds as the season goes  How it spreads: seed
along, but new seeds will always
find their way in and some seeds  Control Methods:
remain dormant in the soil until
ideal conditions present  Pull before it sets seed.
themselves and they germinate, so  Water deeply, but infrequently; this
http://www.frenchgardening.com/aujardin.html?pid=310620990670798
weeding is an ongoing process. tactic will dry out crabgrass roots,
killing the weeds or at least
diminishing their vigor.
If you get in the habit of doing a little weeding each time you
 Solarization can control crabgrass if
work in your garden – or even every day - it won’t become an high temperatures are achieved.
overwhelming task (this is known as the ‘Bradley Method’.
http://www.ppws.vt.edu/scott/weed_id/digis.htm


Crabgrass - Digitaria species Control methods: mechanical

 Control Methods:  Hoeing is by far the easiest
 For chemical control in lawns and  Draw Hoe - the familiar flat-
around ornamentals, use a pre- bladed hoe works best when pulled.
emergence herbicide such as With a sharp blade, you can make
trifluralin; apply it in late winter to quick work of the long rows
early spring, depending on when between vegetable crops.
http://www.ppws.vt.edu/scott/weed_id/digsa.htm
crabgrass germinates in your zone (a http://landscaping.about.com/od/weedsdiseases/ss/weed_fab

local nursery or your Cooperative  Warren Hoe - has a pointed blade
rics_3.htm

Extension Office can provide this heart-shaped blade that is usually
information). For post-emergence used for creating furrows but also
control around ornamentals, apply works well for small weeds and
fluazifop-butyl or sethoxydim.
weeding between rows.
 Scuffle, Stirrup, Hoola or Dutch
Hoe - Cuts weeds at the surface in
a push/pull motion. Easy to use and
nice for covering a larger area.
http://www.aragriculture.org/horticulture/ornamentals/weed_id/crabgrass.htm


13

Garden Weeds - notes

Recommended

Recommended

More Related Content

What's hot

What's hot (15)

Similar to Garden Weeds - notes

Similar to Garden Weeds - notes (12)

More from cvadheim

More from cvadheim (20)

Garden Weeds - notes