Dandelion and crabgrass are two common weeds that spoil the smooth look of turfgrass. Weeds tend to grow in certain habitats and can be managed by understanding their biology. Prevention is always the best cure for weeds. Simply mowing weed flowers prevents them from setting seeds. A treatment plan is developed by learning the growth cycle of crabgrass and dandelion. There are, however, single treatments that can help control these weeds.
Dandelion plants develop in a rosette shape with toothed, oblong leaves and a yellow aster-type flower emerging from the middle. Its single, hollow flower stem grows from 3 to 12 inches in height. Dandelions reproduce all year long with seeds carried on the wind. Its taproot also sends off shoots that form new plants. The long taproot exudes a milky substance when cut.
Crabgrass is a summer annual grass that grows in patches. Large crabgrass is found in garden and landscape areas and smooth crabgrass is found in lawn turf. Smooth crabgrass has short, wide growth and broad leaves. It reproduces by seed when the plant comes to maturity in the fall. Pre-emergent herbicides are an effective control when applied in early spring as new crabgrass seeds begin to sprout.
Glyphosate herbicide has traditionally been the single-treatment choice for crabgrass and dandelions in a lawn. Glyphosate herbicide (Roundup) kills weeds and other plants on contact but many weeds have developed a genetic resistance to the product. Glyphosate in synergy with its "inert ingredients" causes cell death and reproductive abnormalities, according to studies at the University of Caen, France. Many home gardeners prefer a weed treatment plan that is nontoxic.
Nontoxic Pre-emergent Herbicide
Corn gluten meal, a nontoxic herbicide, is applied in early spring and again in mid-August. It is available in powdered or pellet form. Corn gluten meal suppresses crabgrass and dandelion seed growth processes. Germination takes place but the sprout of the plant does not grow. It is effective against weed seeds, not existing plants. It has an accumulative effect on lawn weeds, producing better results each year.
Dandelion and crabgrass grow where turfgrass is sparse. A lawn established on high-quality topsoil is dense, leaving little room for weed growth. Weeds occur where grass is stressed by drought, insect infestation, disease or poor soil. Soil fertilized with homemade or commercial organic compost has the full range of nutrients needed to produce healthy grass. Mowing with the blade set at 3 to 4 inches also slows weed growth.