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Gardening

Keys to weed control rooted in knowledge

By MARY COLLISTER
Published September 23, 2005

The nemesis of many gardeners trying to keep their turf looking good is weeds. I know it seems to be a constant battle at my house. Some say if it's green, it can stay, but I try to have the majority of my lawn in St. Augustine grass. If you have decided to do battle with your weeds, a little information may be helpful.

Weeds are less of a problem in a well managed lawn. When excessive weeds appear, it is usually a sign of weakened grass. This may be caused by insects, disease, improper watering or mowing, poor fertilization or the incorrect pH. You can use herbicides to control many of the weeds, but unless the underlying problems are fixed, the weeds will continue to flourish.

If you decide to use an herbicide make sure it can safely be used on your type of turfgrass. Each variety has a different tolerance to the chemicals. Since no one herbicide will control all weeds, it is important to identify the weeds before applying the chemical.

Proper application is also very important. Make sure the chemical is mixed correctly and avoid excessive overlapping when spraying as this may damage your turf. Some herbicides also warn that application when the temperatures are above 80 degrees can injure your grass. Carefully read all label instructions and warnings before applying.

Pre-emergence application should be made before weed seeds germinate. In our area this is done in December and April. Soil moisture must be adequate both before and after the application.

Postemergence applications should be made when the weeds are still small but can be applied just about all year around. Some of the tougher weeds will require more than one application. With multiple applications you are more inclined to get turf damage as well. If you wait until the weeds are well-established, the herbicide will not be as effective.

Speaking with Keith Capriola from Go For Green fortified my impression that it is them (weeds) against us! But he did assure me that with a proper chemical program and cultural management, weeds can be contained.

Capriola reiterated that it's imperative to keep your turf in top shape and to do this a year-round program needs to be in place. To keep your lawn strong, he suggests applying nitrogen and potassium quarterly. The nitrogen greens up the lawn and encourages strong blade growth while the potassium is for root development.

In the summer Capriola sprays a liquid fertilizer with iron to help keep the lawn green without encouraging excess growth. An insecticide is also included. As an aside, Capriola explained, "The chinch bugs are killing us this year. There have been perfect weather conditions for them, and it is a constant battle to keep them contained."

The list of lawn weeds can fill up a book, but some that Keith pointed out that are extremely hard to control include Jewgrass, torpedograss, and crabgrass. There are not chemicals labeled to take care of these weeds for all grass varieties.

Other weeds that may be a problem include button weed, dollar weed, sedges, beggarweed, oxalis, white clover, dandelions, nutsedge, and pusley. I ran across a good Web site with many pictures of weeds that may be helpful. It is from Virginia Tech, but Florida must share many of the same weed problems with Virginia. Visit http://www.ppws.vt.edu/scott/weed_id/genusindex.htm for photographs that can help you identify your weeds. The cooperative extension service can also help you identify those weeds you are not sure about.

Just like disease and insect problems, Capriola explains that we are seeing weeds new to this area almost every year. This makes it even more of a challenge to control them.

Capriola summarizes by saying that an ongoing, consistent program is what is best. Whether you hire a professional or do it yourself, do a little research before beginning a program. Identify the variety of grass in your yard, learn about the weeds that are a problem in your landscape and put into place a year-round program.

Chemicals are not the only way to eradicate the weeds in your lawn. You may want to rely on removing the weeds by hand. If so, make sure when you dig the weeds out, the roots as well as the foliage are removed. If you have a small area, and a strong back, this may be the best option. Pulling the weeds before they go to seed will also help minimize your problem. Weeds are easier to pull if the soil is moist.

Some will choose to use a nonselective herbicide, which means anything it touches it may kill. So if you get any spray on your lawn, it will also kill that. If you have just a few weeds and can carefully apply the nonselective herbicide to the foliage, this is also an option. It is probably a better solution for flower beds than for turf. You will need to be very careful not to get any of the spray on desirable foliage.

Whatever method or methods you choose to use, you need to be consistent and realize it is a year-round job. If weeds are a problem in your turf, there is no better time to start than right now.

[Last modified September 22, 2005, 09:00:09]