College of Agriculture & Natural Resources

• Canada Thistle

  Canada thistle is a creeping perennial that always colonizes in patches. Plants can reach 1-3 feet high. Canada thistle has an extremely well developed creeping root system that can grow several feet deep.

• Prostrate Pigweed

  Prostrate pigweed is a native mat-forming summer annual weed that invades thin, damaged or under-fertilized lawns. It is common in areas with disturbed soils or neglected areas. Prostrate pigweed lacks the hairs common to redroot pigweed and has smooth leaves.

• Slime Mold

  Slime molds are non-pathogenic fungi that occasionally dwell on many different turfgrass species.

• Smooth Crabgrass

  Smooth crabgrass is the most common summer annual grass problem in managed turf.

• Yellow Woodsorrel

  Yellow woodsorrel is a common summer annual in cool-season turf. Yellow woodsorrel is one of the latest germinating summer annual weeds. Often, infestations of oxalis can be associated with spring-timed broadleaf weed control applications.

• Bull Thistle

  Bull thistle is a clumping biennial that forms a thick taproot in its first growing season. The leaves of bull thistle are covered with 'soft' hairs and needle-like spines on the margin.

• Leaf Spot

  Leaf spot is a warm-weather disease, but the pathogen overwinters as dormant mycelium in infected plants and dead grass debris.

• Germander Speedwell

  Speedwell is often used as an ornamental ground cover and is commonly available at retail greenhouses. Germander speedwell is a perennial that has simple, opposite narrow leaves near the base that are slightly elongated.

• Smut

  The smut diseases are important on many Kentucky bluegrass cultivars and higher cut turfgrass.

• Redroot Pigweed

  Redroot pigweed is a summer annual broadleaf weed that is typically associated with new establishments and other areas of disturbed soil (compost piles, gardens).

• Black Medic

  Black medic is a low-growing creeping weed that is well adapted to many lawn situations. In particular, black medic can be an indication of low soil nitrogen. It is most common to find medic in full sun , low maintenance situations. Black medic and white clover grow in similar situation and are often found growing together.

• Yellow Nutsedge

  Yellow nutsedge is a persistent perennial weed of poorly drained soils. Yellow nutsedge is grass-like in its appearance with parallel leaf veination. The stem of nutsedge is triangular with leaves coming off each corner (three-ranked).

• Dandelion

  Common dandelion is a simple perennial (no branching) with a basal rosette that has deeply lobed leaves that generally point back towards the center of the rosette. Probably the most common weed in maintained turf.

• Prostrate Knotweed

  Prostrate knotweed is a supreme indicator weed. Knotweed is the earliest germinating of all the summer annual weeds. Due to its early germination timing, knotweed is able to claim resources and invade damaged areas before other desirable grasses begin to grow.

• Red Sorrel

  Red sorrel is a perennial weed of low-maintenance sites characterized by dry, infertile and often low pH soils. Red sorrel will survive at neutral pH but is usually not as prevalent because the turf will be more competitive under these conditions.

• Corn Speedwell

  Corn speedwell is an upright, clumping winter annual that produces small purple flowers in the spring. The lower, non-flower, portion of the plant has leaves that are round-to-oblong with rounded teeth on the margin in an opposite arrangement.

• Giant Foxtail

  Giant foxtail is a larger plant than green or yellow foxtail. Giant foxtail will not tolerate mowing and is rarely found in mowed turf areas. It is most commonly a weed of cultivated crops.

• Melting Out

  Symptoms of melting-out resemble leaf spot symptoms and these two diseases are often grouped together. Melting out however is a cool-weather disease where leaf spot is a warm-weather disease.

• Yellow Hawkweed

  Yellow hawkweed is a creeping perennial of low maintenance turf, roadsides and native areas. It can be an indicator of low soil fertility or slightly acidic soils. Hawkweed spreads by stolons and rhizomes creating colonies that form patches.

• Large Crabgrass

  Large crabgrass is a common invader of manicured turf. Large crabgrass has hairs on all surfaces. It can be identified by its light green appearance and swollen, zig-zag nodes.