Common Weeds & Lawn Diseases

Adam’s Weed and Lawn Disease Information Library is your home for information about the most common weeds and lawn problems in Minnesota and Western Wisconsin, their biology, behavior, and of course, how to control them.

Common Chickweed

Common Chickweed is a winter annual plant producing smooth stems and leaves that typically sprawl throughout turf, landscape, and vegetable gardens forming dense patches. The stems of Common Chickweed are around ½” – 1” long. Common Chickweed usually emerge in the fall and may have several generations each year especially during cool wet seasons.

Crabgrass

Crabgrass (digitaria) is in the grass family and is an annual grassy weed that can spread rapidly and will suppress the growth of other plants. With the capacity to spread thousands of seeds (150,000 seeds per plant) during its lifespan, it will thrive in stressed areas of lawns.

Foxtail

Foxtail (Setaria) is an annual that grows quickly during the warmth of summer. A foxtail is a spikelet or cluster of grass that disperses its seeds as a unit, meaning it is a diaspore. There are a variety of weedy grasses with the name Foxtail. In some species, foxtail can be hazardous to dogs and other animals because they have a pointed tip and retrose (backward pointing barbs) that can become lodged in the animal’s ears or nostrils. When mature, Foxtails range from 1’ to 3’ high and branch at the base.

Creeping Charlie

Creeping Charlie (ground ivy) is an invasive, aromatic, evergreen creeper. It is a perennial of the mint (Lamiaceae) family and thrives in moist, shady areas, but it will also tolerate some sun. The variety of ways Creeping Charlie can spread makes it especially hard to kill. It spreads by seeding and rooting at the nodes that stud its vine which means it can be spread by mowing. Also, it can spread by leaving just a small fragment of rhizome behind resulting in the birth of more Creeping Charlie. Humans, dogs, cats, and other animals can get sick from eating large amounts of Creeping Charlie.

Dandelion

Dandelion (Taraxacum officinale) is a common perennial from the Asteraceae family or Sunflower family. Dandelions grow freely especially in areas that are moist with full sun.

Knotweed

Japanese Knotweed is an herbaceous perennial that can be more readily seen during mid-summer and early autumn. This shrub-like plant develops large, dense clumps that are between 3’ – 9’ high. Knotweed can reproduce by seed and by rhizomes that reach up to 15’-18’.

Leafy Spurge

Leafy Spurge is a perennial standing 2-3 ½’tall with smooth stems branching out from a deep vertical root. When stems, flowers, and leaves are broken, a milky-white sap is released. Leafy spurge is an invasive species that is native to Eurasia and is on the control list in Minnesota as a designated MDA Prohibited noxious weed. Therefore, the sale, propagation, or transportation of leafy spurge is not allowed in an effort to prevent seed maturation and spreading of leafy spurge into new areas. Leafy spurge is also toxic to livestock.

Tall Fescue

Tall Fescue grows in clumps, is coarse-textured with wide blades, and can reach up to 6 ½’ high. Tall fescue is often misidentified as crabgrass, but they are very different grass types. As one of the most commonly used turfgrasses, tall fescue adapts well in many areas of the country, tolerates shade better than other cool-season grasses, and establishes easily from seed.

Yellow Nutsedge

Yellow Nutsedge can be found wild, as a weed, or as a crop. It is an invasive species and is often found in wet soils such as rice paddies and peanut farms as well as well-irrigated lawns and golf courses during warm weather.

Thistle

Thistle is the name used for a group of plants characterized by sharp prickles all over the plant including the stem and the flat parts of the leaves. Most thistles have stiff spines on the margins. Thistle can be biennial or perennial weeds with a variety of species primarily in the Asteraceae family.

Wild Violet

The Common Blue Violet (Viola sororia) is an annual or short-lived perennial that grows up to 6” wide and 4” high. The flowers are a bit taller than the leaves with each leaf up to 3” long and 3” wide.

White Clover

White Clover (Trifolium repens) is a long-lived perennial legume or winter annual legume. White Clover is a popular choice for systems that are “living mulch” and are planted between rows of irrigated vegetables, fruit bushes, and trees. It is also a forage species for livestock. Originating in Europe, it is now one of the most highly distributed legumes in the world. White Clover usually grows to about 6” – 12” high, but even when mowed or grazed, White Clover can thrive. Also, White Clover can hold up well under heavy field traffic. White Clover reproduces either by seed or vegetatively often forming colonies. Cool, moist conditions and shade help white clover flourish.

Fairy Rings

Fairy rings can be caused by any number of fungi.

Leaf Spot and Melting Out

Leaf spot and melting out are different diseases with similar symptoms, caused by different fungi. Melting out (caused by Bipolaris sorokiniana) usually appears in April and May during cold, rainy weather. Leaf spot (caused by Drechslera poae) is a summer disease that requires long dew periods, warm evening temperatures, and plenty of rain.

Powdery Mildew

Powdery mildew is a common fungal disease most often found in shady areas of the lawn. Powdery mildew can occur throughout the growing season but is usually most noticeable in the spring and fall.

Snow Mold

Snow mold, also known as snow rot, is a common problem in areas with late snow covers and cold, damp springs. Snow mold flourishes under snow or wet leaves during the winter months. Snow mold is more prominent when the winter’s first snows were early and heavy enough to cover ground that wasn't yet fully frozen. Conversely, a cold winter without much snow cover results in less snow mold in the spring.

Turf Patch

Common turf patch diseases include Yellow Patch (Rhizoctonia cerealis) and Summer Patch (Magnaporthe poae), as well as Necrotic ring spot. (See Necrotic ring spot)These diseases are caused by fungus that affects the roots of the grass.

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