While winter-dormant St. Augustine lawns have yellowed, something is going on under the soil.
Winter weeds are beginning to germinate. And a lot of weeds do well here. Plantain weed, nutsedge, henbit, spurge, purslane, chickweed, and thistle are a few of the unwanted guests that plague our lawns in late winter and early spring.
Don’t despair. St. Augustine is the best weed-suppressing grass there is, followed only by Zoysia. Both are aggressive plants. If properly maintained, they will keep the weeds to a minimum, if not entirely eliminate them.
What weeds like
Winter weeds start poking their heads up when the first string of warm days come in January or February. The best method to get rid of them is merely pulling them up and disposing of them in your green waste. Mowing them down before they seed also gets rid of them.
Weeds do like compacted, poorly-drained soil, bereft of available minerals, nutrients, and organisms. Residents who apply organic matter to lawns in mid-fall and mid-spring have already established a strong defense against weeds. And although these are ideal times to spread organic matter, anytime is okay. Aerating the lawn before adding organic matter is another step in the weed war. The organic matter helps soil drain and simultaneously holds enough water to establish a healthy root system and is the first and most crucial step in having a beautiful lawn.
But weeds are ornery and persistent. Even in the most well-cared-for lawn, it’s probable that a few plantains and thistles are going to pop up. While “chemical” herbicides may not be the best choice, few products are available to the environmentally-conscious homeowner.
Don’t use “weed and feed”
Don’t fall for the advertising that “weed and feed” products are suitable for your lawn. They’re not! The time to weed and the time to feed are different. Putting “weed and feed” down in February will prohibit weeds, but the fertilizer part of the product (the “feed” part) shouldn’t go onto the lawn until another month or two. By the time the lawn needs the fertilizer, it has already been leached out of the soil. Don’t waste your money,
Aerating and composting
If your soil is heavily compacted, aerate your lawn in late August to early September and again in late April to early May. Then topdress your lawn with 1/4 to 1/2 inch of good, organic compost. If the soil is still compacted, do the same again. After your soil seems loose and friable, topdress with compost every year or two.
Vinegar, ammoniated soap of fatty acid
Agricultural vinegar is available at many garden stores. It is tried and tested and will destroy even the most persistent weeds. It even works on that superweed – nutsedge. Just be careful. Agricultural vinegar is much stronger than the standard white vinegar that most people keep in their kitchens. Wear gloves (preferably rubber gloves) when applying.
One application of agricultural vinegar eliminated a sizeable stand of nutsedge growing in a community garden near me. Ammoniated soap of fatty acid or potassium soap of fatty acid are also effective herbicidal treatments for weeds, though more effective on plantain, wood sorrel, and spurge.
Whether using vinegar or soap of fatty acid, it’s not necessary to spray a whole area. Simply spray each weed. A spray bottle works well. However, remember that vinegar will kill everything it touches, so be extremely careful when using it on your lawn.
If you follow these recommended steps, you can reduce or eliminate weed infestations, have a beautiful green lawn, and, as a bonus, have little or no fungal or bacterial infections in your yard.