Weeds and How to Manage Them

Weeds and How to Manage Them

A plant growing where you don’t want it to - this is a working definition of a weed.  Weed seeds can be carried into your yard either by birds or wind.  There are two basic groups of weeds - those that are grasses and those that are broadleaf, which can be classified as annuals or perennials.  Annual weeds grow from seeds and grow, flower, produce seed, and die within one season.  Perennial weeds can live for several years. The control methods you choose will depend on what type of weed you are dealing with.

Control

If you only have a few weeds in a relatively small area, mechanical removal is often the most desirable method.  This can be accomplished with sharp hoes, shovels, or hand pulling.  If applications of herbicides are warranted, it is important to select one that will target the weed you are dealing with and not harm surrounding vegetation.  If you use grass killer on the crabgrass or nut sedge growing in your hybrid Bermuda lawn, it won’t discriminate and will kill any “grass” it contacts.

For control of nut sedge (nut grass) in lawns, several applications of the product Manage in September will provide effective control.  Some follow-up may be necessary.

In lawn areas the best weed control is a healthy lawn.  Turf will out-compete most weeds, and regular mowing will remove the growing tips of the weeds.  Any chemical weed control should be practiced only on well-established lawns; newly installed or seeded lawns are often injured by weed control agents.

In gravel areas, both annual and perennial weeds can be controlled with the application of a post-emergent herbicide.  Post-emergents work when weeds have already sprouted and are growing.  The most common products for this application contain Glyphosate (Roundup) or Glufosinate (Finale).  These herbicides work by moving the product through the leaves to the roots where they interfere with the growth process.  Both these products are non-selective, meaning they will kill any growing vegetation, both grass and broadleaf. Spot treatment with Glyphosate is effective especially in dormant winter Bermuda lawns.

Pre-emergents work very well in preventing weed seeds from sprouting and work best in gravel areas.  Do not use a pre-emergent if you plan to establish a Bermuda grass lawn by seeding.  The same is true in the fall if you overseed your hybrid Bermuda or Bermuda grass lawn.  The herbicide will prevent the winter rye grass seeds from sprouting!

Many pre-emergents are available from your local nursery or home improvement store.  For example, a common pre-emergent herbicide has a chemical name of: 3, 5-dintro-N4, N4-dipropylsulfanilamide.  The common name is Oryzalin.  Ask the sales staff for assistance if you are unsure which product is a pre-emergent.  Apply twice a year - in April for control of summer weeds and in September for control of winter weeds.

Caution: Never use a total vegetation killer that is a soil sterilant.  These products kill existing vegetation, persist in the soil for many years, and can leach into surrounding areas seriously affecting or killing plants there.  If you have an area in your yard where nothing will grow, a soil sterilant like Triox may have been applied there in the past.

Be careful when using products that contain 2-4-D.  They are designed to be applied when the temperatures are cool.  During most of the year this product volatilizes (turns to a gas) and can cause damage to surrounding vegetation as it drifts through the air.

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Remember!  Always follow label directions exactly!  We sometimes think if a little is good, more is a whole lot better.  The average homeowner applies 9 times more chemicals to their property than a farmer does on the same size land.  With herbicides and insecticides, this can be deadly - to plants, pets, and humans.  Wear protective clothing and avoid skin contact with the product.

Common broadleaf weeds: Purslane, goosefoot, pigweed, puncturevine, London rocket, bur clover, cheeseweed, tumbleweed, silver nightshade, prostrate spurges.

Common grass type weeds: crabgrass, Bermuda grass, nutgrass (not really a grass), bromegrass, orchardgrass, common foxtail.

Cathy Rymer

Water Conservation Specialist

Town of Gilbert