Gardens

Winning the War on Weeds
Armed with the right information and a little resolve, you will be well on your way to growing a healthy, weed-free lawn.

by Sid Mullis

A beautiful lawn is a tremendous source of pride for many Augusta homeowners. But the cultivation of such a lawn is the result of much hard work not the least of which is winning the war on weeds.
There are a variety of ways weeds invade your lawn. They can be in the sod you purchase; animals and birds can transport them as can wind and rain. Regardless of how they get to your yard, weeds have an amazing ability to survive the harshest conditions. Some seeds can lay dormant for years and suddenly germinate while other species can produce thousands of seeds in just one season.

However, battling weeds doesn't have to be complicated. With a better understanding of how and when weeds germinate and grow, and how to incorporate proper control methods, you can have a beautiful, weed-free lawn that is the envy of your neighbors.

According to Tony Brown, department head at Empire Tree and Turf Company, the average homeowner understands the value of a good weed management program. They just don't always know how to get there. "The base of knowledge is out there, but it's not always reaching the homeowner that is trying to do it. Some people have made it a hobby to learn and apply good techniques and are able to do a good job on their own," he says.

But for those who don't have the time or patience for the trial and error route to a beautiful lawn, here's all the information you need to cultivate a healthy, luscious lawn.

What Is A Weed?

Some plants are considered to be weeds by some people but not by others. The defining factor depends on where the weed or plant is growing. For example, if you have a bermuda lawn and centipede grass invades it, then centipede would be viewed as a weed by you. And if that bermuda grass invades your flower beds, it might well be deemed a weed. So in view of this, the best definition of a weed is simply "a plant out of place."

By most definitions weeds are major pests. They not only detract from the natural beauty of your lawn, they also compete with grass for sunlight, moisture and nutrients. And unless a regular weed-control program is in place, they can quickly take over.

There are three primary methods of controlling weeds in your lawn. Each method, when used alone, will not usually get the job done. To consistently control lawn weeds, you must use a combination of the following three methods.

Cultural Practices

According to Brown, the first line of defense against weeds is to promote vigorous growth and development of your lawn. "Weeds do not easily invade turf grasses that are properly fertilized, watered and mowed at the correct height and frequency," he says.

Take the following steps to help assure healthy turf grass and prevent weeds in your lawn:

Choose a grass that is appropriate for the site. For example, don't try to grow bermuda in a heavily shaded yard because it needs a lot of sun to thrive.

Apply the proper amount of fertilizer and lime during the correct times of the year. Soil tests can be crucial to your success because they provide pH and nutrient levels. Hybrid bermuda requires four to six pounds of nitrogen per 1000 square feet per year, while centipede requires only one pound or less.

Water properly and only when needed. Frequent shallow watering will encourage weed seeds to germinate and grow. The average lawn should be watered one inch, once a week. Variations come into play depending on the grass species and soil type. Grass roots will grow deeper and seek water when not watered too frequently. Invest in a rain gauge so that you always know how much rain you're receiving.

Mow grass at the correct height and frequency. Cut it often enough so that you remove one-third of the leaf blade. Just as they have different fertilizer needs, various turf grasses need to be mowed at different heights too. Frequent mowing can reduce certain weed species because it causes them to deplete their underground food reserves.

Control insects and diseases. Either pest can decrease the stand of turf grass, which favors the growth of weeds.

The impact of good cultural practices on a weed-control program cannot be over-emphasized. "Properly maintained turf grasses are more competitive with weeds than turf grasses that do not receive good cultural practices," Brown says. The use of herbicides alone will not result in a high-quality, weed-free lawn.

Hand-pulling annual weeds is safe and effective in many cases. However, it is time consuming and not effective for the control of most perennial weeds. Hand-pulling a new weed when it first appears in the lawn will help to prevent the spread of that weed.

Herbicides

A herbicide is a chemical used to control the growth and development of weeds. Before a herbicide is approved for use in residential lawns, it is thoroughly tested by chemical companies, land grant universities and various federal agencies. It must be proven safe to humans, the environment and turf grasses, and it must effectively control weeds. Herbicides are an essential component of a weed-control program. They are applied at specific times of the year and will control only certain weed species. Also, many herbicides cannot be used on every turf grass species. The product label is the best reference for safe and effective use of any herbicide. Always read the label prior to using this or any chemical.

One reason weeds are such a pervasive problem is they grow 365 days a year. "There are winter weeds and summer weeds. And we have annual, biennial and perennial weeds," Brown says. Knowing more about the life cycle of weeds and when they germinate is an important part of controlling them. Annual weeds complete their life cycle in less than one year and reproduce only by seed. Annuals are made up of summer and winter weeds.

Summer annuals germinate in the spring or late winter months, live during the summer and mature in the fall. Examples are crabgrass, goosegrass and lespedeza.

Winter annuals germinate in the late summer and early fall months, live during the winter and die in the late spring and early summer with the onset of hot weather. Examples include annual bluegrass, chickweed and henbit.

Brown says winter weeds are the most abundant and the variety people most want to control. "Grass is dormant during this time so it cannot compete with the weeds. Also, since the grass is brown they stand out more in a lawn," he says.

Biennial weeds live for two years. During the first year, they germinate from seed and produce vegetative growth. In the second year, they form a seed stalk, produce seed and die. Biennials are not as common in lawns as annual and perennial weeds. Examples include wild carrot and common mullein.

Perennial weeds are usually more difficult to control than annual weeds. In addition to reproducing by seed, perennial weeds reproduce by vegetative structures such as stolons, rhizomes, tubers, fleshy taproots and bulbs. Examples are bahiagrass, wild garlic, nutsedge and dandelion.

Application Schedule

Now that you have a good understanding of weeds and the proper use of herbicides, the following schedule will help you keep weeds to a minimum in your lawn.

Fall. When temperatures drop to 55-60 degrees at night, apply preemergence herbicides to control winter annual weeds. This is usually sometime between mid-September and early October.

Spring. When daytime temperatures reach 65-70 degrees for four to five days, apply preemergence herbicides to control summer annual weeds such as crabgrass and goosegrass. An indicator that the air temperature is sufficiently warm to promote weed seed germination is when crabapple and forsythia bloom. This is usually between mid-February and early March.

Products And Application

The main preemergence products available to consumers are listed below (common name followed by various trade names):

• Benefin (Balan, Crabgrass Preventer)
• Oryzalin (Surflan)
• Pendamethalin (Halts)
• Benefin + oryzalin (XL)
• Atrazine (Atrazine, Purge II, Bonus S)

Following are some added tips on applying postemergence herbicides:

• Apply in the fall and late spring. Air temperatures are cooler, resulting in better turf grass tolerance to herbicides.
• Do not apply postemergence herbicides to turf grasses and weeds that are stressed due to high temperatures or drought. Turf grass tolerance to post-emergence herbicides decreases at air temperatures greater than 90 or when turf grasses are drought stressed. Also weed-control is less effective when herbicides are applied to weeds in a stressed condition than when applied to actively growing weeds.
• Do not apply postemergence herbicides during green-up in the spring. The risk of injury from postemergence herbicides is greater during the green-up process than when turf grass is fully dormant or actively growing.
• With many hard-to-kill weeds, particularly perennial weeds, you may need to use multiple applications to kill them.

Below is a list of the most common postemergence herbicides available to consumers:

• Sethoxydim (Vantage, Poast)
• MSMA (MSMA, Crabgrass Killer)
• 2,4-D + MCPP + dicamba (Weed-B-Gon, Ace Lawn Weed Killer, Southern Weed Killer for Lawns)
• Triclopyr (Weed-B-Gon, Chickweed, Clover and Oxalis Killer)
• Atrazine (Atrazine, Purge II, Bonus S)
• Imazaquin (Image)
• Halosulfuron (Manage)

Now that you have a better understanding of how to control weeds in your lawn you can get started winning the war on weeds so that you too can have a lawn that is the envy of the neighborhood.