There are dozens of different lawn weeds, but the greatest problems are caused by a select few. While it is tempting to simply use heavy doses of broad-spectrum chemical killers to eradicate weeds, there may also be more specific remedies for specific weeds. Plus, some weeds are remarkably resistant to herbicides, responding better to different methods of control.
Dandelions (Taraxacum officinale and Teracacum erythrospermum)
Unlike many lawn weeds, this one is indigenous to North America, not a foreign invader.
Purslane (Portulaca oleracea)
The Spruce / David Beaulieu
Black Medic also called Yellow Trefoil is an annual species so it only lives one year but it makes a lot of seeds that can remain viable for several years. It’s seeds germinate in the spring and are capable of establishing in drought-prone or disturbed soils. Black medic is a legume, meaning that it has the capabilities to fix its own nitrogen; thus, allowing it to out compete turf in nutrient-poor soils as well. These factors, in combination with its ability to tolerate low mowing heights, make black medic a common weed in lawns.
Black medic is not shade tolerant, therefore the development of a thick, dense turfgrass canopy helps improve competition against it. Unfortunately repeated hand pulling is really the only good option, especially before it start to make seeds. You can also try using either a vinegar based or citric acid organic herbicide.
Water the lawn once more, don’t saturate the grass, since that would wash the sugar away. Spray the lawn with a light mist, providing just enough water to re-moisten the blades of grass and coax the sugar down into the soil and the roots of the lawn.
The best defense is a good offense. Regular overseeding of your lawn will encourage a dense root system which will not provide space for Crabgrass to grow. Crabgrass is very rare in thick, healthy lawns that are mowed to a height of 3 inches (7.6 cm) this helps to keep the soil cooler thus inhibiting germination of Crabgrass seeds.
If you have had Crabgrass in the past, in early spring give the area a hard raking to dethatch it and remove the debris. You can then apply corn meal gluten, which will act as an organic pre-emeregent herbicide. Please note that since corn meal gluten is a pre-emergent, you cannot overseed your lawn until the fall if you use corn meal gluten in spring. The best way to organically control Crabgrass is to ensure that you keep your lawn mowed in late summer when the Crabgrass is putting up its purple seed stalks. This will prevent it from making seed for the future.
Non-organic Solution: Spot spay in early spring or early fall with a non-selective herbicide containing glysophate (Round Up). As this also kills turf, you will need re-seed the areas you have sprayed.
Apply the herbicide during a dry period. Wait several days after your last watering and do not spray the herbicide if you may get rain four hours after application or if you expect heavy rains to follow in coming days. Water will wash the chemical away and it may not have the chance to do its job before that happens.
Select an appropriate herbicide. Products that contain MSMA or products with a chemical called bentazon work best. Nutsedge is a common enough problem, so herbicides that work against the weed will be labeled as ” nutsedge or nut grass killers.”
Read the instructions on the label of your herbicide bottle to determine how to apply it properly. You will usually spray diluted MSMA herbicide over your entire lawn. For instance, the instructions may tell you to mix 1.5 ounces (45 milliliters) of chemical into 5 gallons (20 liters) of water to treat 1000 square feet (92.9 square meters) of lawn.
Allow your lawn to grow for a few days prior to application. Herbicides works best when the nutsedge is growing vigorously and may not be as effective if applied immediately after cutting it down. Wait two or more days after your last lawn mowing before applying the chemical to the lawn.
By seeds and lower stem pieces that root.
Broadleaf perennial with shallow, fibrous roots.