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Weeds Identification & Control
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Bulletin #TP2625 |
Horticultural Observations for Healthier Landscapes |
The Plant Kingdom includes: Trees, Shrubs, Flowers, Groundcover and houseplants.
Because this discussion will include methods for controlling or killing weeds,
it is very important to remember a weed is a plant; One growing where you do not
want it to grow - and usually invasive (it survives and reproduces easily).
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DIFFERENT GROUPS OF HERBICIDES Selective Nonselective ◊ Bermuda ◊ Mallow ◊ Oxalis ◊ Purslane ◊ Spurge DIFFERENT
GROUPS OF HERBICIDES For weed killers, there
are two basic groups of post emergent herbicides, selective and nonselective.
Selective products kill weeds listed on the label with little or no effect to
other plants. Nonselective products kill weeds listed on the label but will
severely injure or kill nearly all other plants as well. Nonselective, foliar
(applied by wetting the leaves) products are safe to use on weeds in tree wells
and around ornamental shrubs as long as you don't
get solutions on leaves of the desirable plants.
Understanding the
difference in pre-emergent and post-emergent herbicides is important. Pre-emergents
kill germinating seeds and not established plants. They're most
effective when applied before weeds begin showing up.
WEED
VARIETIES AND CONTROL Bermuda
Controls: Hand weeding is not very effective because the
smallest stem or root piece will start a new plant.
Crabgrass
Controls: Good cultural practices and regular fertilization
keep a thick, healthy turf which prevents crabgrass from gaining a foothold in
your lawn. Dig out any large clumps (crabgrass grows in clumps).
Dallis
Grass
Controls: Pre-emergents are only effective on the seeds - not the rhizomes.
Dig up the clumps and follow with pre-emergent.
Spot spray with Fenoxaprop p-ethyl if there is too much for digging up clumps.
Bur
Clover
Controls: Follow good maintenance and fertilizing practices
to keep a strong, thick turf. Spot spray with a selective
herbicide like (2-4-D)
to eradicate established weeds (plants). Watch
over-spray (or mist) and wind drift around desireable plants in hot weather
Curly
Dock
Controls: Hand pull or spade to remove large plants. If
many, smaller plants are found, use a selective broadleaf weed killer (2-4-D). As
always, watch over spray and wind drift.
Dandelion
Controls: A thick, healthy turf will restrict this pest.
Apply a pre-emergent (Prodiamine or Corn Gluten) in early spring and use a selective broadleaf weed killer
like (2-4-D) as needed throughout the growing season.
Watch over spray in hot weather
Mallow
Controls:
Keep a thick, healthy Lawn. Use a pre-emergent
(Prodiamine or Corn Gluten) in early spring to stifle seeds.
Spot treat individual plants with a broadleaf
weed killer (2-4-D).
Oxalis
Controls: Apply a pre-emergent (Prodiamine or Corn Gluten) in early spring. Spot treat
existing plants with a broadleaf weed killer (2-4-D) Watch
over-spray in hot weather and drift on windy days.
Pull them by hand, but don't forget the pre-emergent or its coming back.
Purslane
Controls:
A late spring application of pre-emergent
herbicides will control infestations. Pull the shallow rooted plants whenever
you see them.
Spurge
Controls: Prevention is the best cure.
Keep your lawn thick and healthy. Apply a pre-emergent (Prodiamine or Corn Gluten)
in late winter and summer (if this pest is bothering you).
Pull large plants very carefully so you Don't
break the taproot (or apply 2-4-D first).
Why are weeds spreading in my yard?
An important question to answer if you'd like them to stop.
Lawn weeds
6) mowing too close or scalping,
5) too much shade,
4) insect or disease damage.
3) too little or too much fertilizer
2) too much traffic
1) the number one reason is "weed seeds blowing onto the lawn."
Flower or Shrub bed Weeds
4) too much shade
3) insect or disease damage
2) too little or too much fertilizer
1) the number one reason is "weed seeds blowing into the bed."
Weeds in the Vacant areas of the Landscape
3) too much sunshine
2) too much moisture
1) the number one reason is "weed seeds blowing onto that area."
Prevention and Control
Prevention of weeds is the best control method, and wild seeds are the number one cause.
There really is no practical way to keep tiny weed seeds from blowing into your
lawn or garden. Plus sometimes they arrive in your lawn from foot traffic.
There is a way to make it very difficult for a seed to germinate.
Another successful method of making seed germination difficult is the use
of surface mulch. A shredded mulch is most successful and any mulch
needs to be at least 2 inches deep. Why? If a seedling can not gain
access to the sun within 2 inches of growth - very few will survive.
It's practical to use surface mulch on shrub areas, flower and vegetable beds.
Other methods of Prevention
Use the proper fertilizer for your various plants and apply at least twice a year.
Keep them healthy and they often can defend themselves. Don't practice
shallow irrigation on shrubs and trees - deep water and allow the surface to stay dry longer.
This also reduces your water bill. If you see signs of isects or disease,
take a specimen into a local nursery that has trained plant science people,
and find out how to correct this.
Once Weeds are Established
Killing and removing them is the next course of action.
If the weed has already produced seeds, we have a complication;
We can kill the visible weed and remove it - but the little seeds
will germanate and the weed will return.
Pulling weeds is not really my idea of fun, and if you don't get the whole root
along with the surface foliage, it is going to come back. It is hard to now if you pulled the whole root!
A good idea is to use the right kind of post emergent herbicide, and
allow a week for it to translocate within the plant from the foliage to the roots, before
removing the weed. This technique utilizes the least amount of time & labor
in order to get weeds under control.
Understanding Herbicides
The chance of quick success is very limited if one does not
understand the various herbicides that are available.
Safety is Important!
To grow produce and claim it is "organic" there are regulations to comply with.
Horticultural Vinegar is an herbicide that can be used and remain compliant
with "organic" regulations. Though compliant, it is not organic, but it is natural.
It is kind of expensive and can be dangerous to the person
applying it. So, overall safety has a question mark.
If Safety is your prime concern, don't become obcessed with
"organic". There are many safe (when used as directed) pre and post emergent
herbicides to choose from. It is hoped that the information
below will help you to make a selection that works for your priorities.
As is the case throughout Garden Galaxy pesticide discussions; we will reference
the actual chemical name and not the Brand Name that conbtains that chemical.
You can simply do an internet search using the "chemical" name and many options for purchase will arise.
There are two reasons we avoid brand names:
1) Brands periodically change the chemical they use.
2) We try to avoid
promoting any specific brand, manufacturer or distributor.
Your Trust in our Advice
is paramount.
Avoid application on windy days - the mist will travel (further than you think)
and damage or kill desirable plants in the area. Apply as closely to
the invasive weed you're trying to irradicate as possible.
[Grass killer] Fluazifop-P-butyl; "Fusilade" & "Grass B Gon" are common names for this
herbicide that selectively kills various species of grassy weeds, while
leaving most broadleafed plants alone. As is always the case; avoid spraying on windy days, and read the product label
to see what broadleafed plants may be suseptable & for safty of use.
Glyphosate: There has been much controversy over glyphosate
due mostly to the chemical penetrating into various food grains
that have been designed to tolerate this product. Applicators who
were routinely exposed to glyphosate and did not maintain adequate
personal protection from the chemical were also injured.
Care should be used when applied glyphosate as it will attack any surface roots
where it's applied, and of course chemical drift due to windy conditions,
If kept away from edible plants, and when proper personal protection is used;
glyphosate can be effective and reasonably safe.
There are also non-selective herbicides that are designed to be applied into the soil
and these also translocate within the soil. These are applied as a drench, and due to the dangers of
incorrect application, these should only be used by trained and certified professionals.
Corn Gluten
Because of this products growing popularity, there are brands on the market
with more economical pricing.It is safe to use, and most brands
include a reasonble portion of nitrogen to help feed the plants.
It can be used on lawns, flower and veggie beds. Where there is
more traffic or watering, the product may need to be applied more frequently
in order to be effective. Continued use will reveal what frequency is necessary,
but typically it should be applied in spring and fall.
Prodiamine & Dithiopyr
are two common and popular pre-emergent chemicals. These are
both good products and they both are easy to find and apply.
It is important to know that no single pre-emergent works
for all weed types. Prodiamine is less expensive and stays put in your soil longer.
(top)GRASSY
WEEDS:
is a common turf grass invader that becomes a nuisance weed by
spreading where it isn't wanted.
A vigorous perennial that thrives in drought prone climates,
it's often mistakenly called crabgrass which is a different kind of weed altogether.
Bermuda grass spreads underground by rhizomes and on the surface by fine,
easily transported seed. It has a very fine, pointed leaf and spreads rapidly
by use of runners.
Fluazifop products are generally effective during the warm season.
Use caution (as described above). Several applications may be needed for complete control.
Glyphosate products are
effective when applied to leaves of actively growing bermuda.
Several applications may be needed for complete control.
If runners are present in desirable turf, wipe them with a cotton rag soaked in the herbicide'
This will avoid any residual turf damage caused by spraying.
Use of herbicides while bermuda is dormant (brown) will have
no effect.
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is a warm season annual (becomes perennial in climates without frost)
that spreads rapidly through
seed dispersal. A clumping, broad leafed, shallow rooted plant, it will thrive
in a thin, under-fed, over watered lawn and will eventually take over if left
unchecked.
Apply a pre-emergent in February to prevent seed
germination. If the weed appears, spot treat with Fenoxaprop p-ethyl. This chemical
is mostly safe for cool season grasses, yet effective on Crabgrass.
Anytime you are using a grass killer on your lawn - caution is advised. Spot
test at first to see how the desirable grass does.
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is a perennial that thrives in summer. Large flat
stalks grow from a central crown-shaped ring 4-8 (and more) inches across. It spreads
through rhizomes and seeds and can be difficult to spot in fescue lawns.
It will rapidly outpace normal fescue growth and then
is easy to identify in order to eradicate.
Caution when spraying in the summer, hot weather may have adverse effects on desireable grasses.
is a low-growing,
trailing, densely matted, annual weed that reproduces by seed. Its
clover-like leaves and yellow blooms will begin to dominate any poorly
maintained lawn in early summer. If not controlled, it will crowd out lawn
grasses and leave bare spots.
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is a large, broadleaf
perennial with green leaves. It sends up a tall, narrow spike of greenish
flowers from the center of the plant. Large, individual plants make it easier to
spot.
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is a
broadleaf perennial with prolific yellow flowers and jagged green leaves. It
spreads by seeds AND sprouting crowns from the roots. A single taproot will
re-grow if broken off at or below ground level. Seed can germinate year-round.
Post-Emergent and Pre-Emergent are advised if
your having problems keeping this weed away.
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is an annual that reproduces through seeds. It
has large, fan-shaped leaves at the top of a long stalk and flourishes from
early spring through fall. Mallow is usually found in thin, poorly maintained
lawns, or flower and shrub areas.
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is an aggressive, clover-like perennial which
develops a vigorous, spreading root system. Small, yellow flowers form seed
pods that can shoot seed up to 6 feet when ripe.
This weed can take over if not controlled.
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is a low-growing succulent. Normally an annual (where winters are cold)
that reproduces by seeds.
It thrives in hot, dry summers and shows up later than most weeds
in bare spots, flower and shrub beds and thin lawn areas.
(top)
is a
low-growing, spreading annual that can live through a mild winter. It forms
dense mats of small oval leaves over a central taproot and spreads
itself through heavy seed production.
Spurge is very common and noticeable along the edges of lawns, driveways and sidewalks.
It also thrives in bare spots and thin turf
areas.
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