Many types of weeds are found in lawns in Minnesota, most of which enjoy the cooler climates that the state offers. Some weeds are broadleaf plants, while others are grass or grasslike. Some weeds in Minnesota lawns are annuals, while others are perennials or biennials. You’ll need to properly identify the type of weed in your Minnesota lawn to know the best way to get rid of it, whether with post-emergent, pre-emergent or non-selective herbicides.
Perennial Broadleaf Weeds
Identify dandelions in your lawn by their broad, jagged-edged leaves. Dandelions sprout long, slender stems with yellow, round flower heads.
Look for burdock invading your lawn by studying the large leaves that have tiny hairs covering the undersides. Burdock, which is a biennial or perennial weed, blooms purplish-lavender flowers surrounded by hooked bracts that become burs. The flowers grow at the ends of 3- to 6-foot-tall stalks from July until September.
Spot plantains growing in your Minnesota lawn by looking for their broadly oval leaves that narrow sharply toward the bases. Broadleaf plantains have 6- to 12-inch greenish flower spikes that grow from the center of the plant.
Identify thistles in your Minnesota lawn by looking for tall-growing weeds that usually have coarsely lobed leaves with stiff hairs or spines on the upper surfaces and woolly, dense hairs on the undersides. Thistles often produce upright, thick flowering stems with prickly flower heads.
Spot clover growing in your Minnesota lawn by looking for its green leaves with slight white crescents that grow in groups of three. Clover is low-growing and forms a dense mat with smooth, round stems that creep along the ground and bear clusters of spherical white flowers from June until September.
Look for weed with creeping above-ground stems, or stolons, to spot ground ivy or creeping Charlie in your Minnesota lawn. Creeping Charlie stays green year-round, has rounded leaves with scalloped edges that are arranged opposite each other along the stems and sprouts purple, tube-shaped flowers on upright stems in spring. The leaves emit a mint-like fragrance when crushed.
Spot yarrow by looking for its unbranched, 2 1/3-foot-tall stems and leaves with pointed lobes or teeth on the edges. The leaves are 1 inch wide and 1 to 6 inches long with short hairs, composed of alternately arranged, smaller upper leaves and larger lower leaves. The yarrow often resembles a fern and produces a flat-topped, rounded cluster of white or pinkish flowers.
Identify spurge, which emerges in Minnesota lawns in April, by its clump-like growth pattern with multiple upright stems. Spurge weeds produce smooth-edged, narrow leaves that are bluish-green and turn yellowish or reddish-orange in late summer. Spurge also bears flat-topped clusters of showy yellow flower bracts in May.
Annual Broadleaf Weeds
Spot mallow in your lawn, which grows either annually or biennially, reaching heights of 4 to 12 inches with alternately arranged, crinkled, kidney-shaped leaves that have finely toothed edges. The leaves and stems have short hairs and the white, purple-tinged, five-petaled flowers bloom from May through October.
Look for a low-growing, spreading annual weed in your lawn to identify black medic. Black medic can spread up to 2 feet wide, with round or oval, alternately arranged leaves covered in tiny hairs and growing in clusters of three leaflets. The stems have tiny hairs and the flowers that grow in clusters are small, spherical and yellow.
Identify henbit by its square, nearly hairless stems that have upturning tips and rounded, scalloped-edged leaves that grow opposite each other in pairs along the stems. Henbit grows 3 to 15 inches tall and blooms in pink to violet, tube-shaped flowers in early spring. The leaves have a mint-like odor when crushed.
Look for knotweed emerging in early spring in your Minnesota lawn. Knotweed has small, narrowly oval, bluish-green leaves and small white flowers that bloom from June until late fall. The leaves grow alternately arranged along the stems with a swollen node at each joint that’s surrounded by a papery structure.
Spot chickweed, a winter annual plant, thriving in early spring in matted clumps of freely-branching stems, which are covered with rows of fine hairs and creep along the ground. Chickweed has smooth, oval leaves that grow opposite each other along the stems and delicate flower stalks with clusters of small white flowers that have five deeply notched petals.
Annual Grassy Weeds
Look for a grass weed growing in small clumps and reaching heights of no more than 10 inches to spot annual bluegrass invading your Minnesota lawn. Annual bluegrass has boat-shaped, upward curving leaf tips and will produce whitish-green seed heads even when you mow it close to the ground.
Identify barnyardgrass by its long, smooth, light-green leaves and upright, multiple-branched flower panicles that are greenish-purple. Reaching heights of 1 to 4 feet, barnyard grass has flat stems and greenish, pink, purple or reddish flower heads.
Spot crabgrass growing in multiple-stemmed clumps and thriving in the midsummer heat. Crabgrass has alternately arranged, slender leaves and purplish, slender flower heads.
Look for an upright grassy weed with large seed heads to identify foxtails. Foxtails are tufted, coarse weeds that emerge in Minnesota lawns in late spring and summer.
Identify goosegrass growing in your Minnesota lawn by looking for its folded leaves and flattened stems, forming a whitish-silvery mat and becoming a pale-green clump. You’ll see goosegrass growing in thinned lawn areas with short, stout flower stalks and short, stiff seed heads.
Perennial Grassy Weeds
Spot quackgrass emerging in your Minnesota lawn during spring and fall. Quackgrass has 2- to 12-inch, bluish-green leaves that are less than ½ inch wide and sometimes appear to be twisted. Quackgrass spreads by underground stems, or rhizomes and produces spike-like flower heads.
Look for a coarse, tough, dark-green grass with flat, stiff leaf blades to identify tall fescue invading your lawn. Tall fescue forms clumps with open, loose and small flower spikes, usually growing most vigorously in fall and spring.
Identify creeping bentgrass by looking for its purplish to reddish lower grass shoots and bluish-green leaf blades that are narrow, pointed-tipped, flat and smooth-edged. Creeping bentgrass emerges in Minnesota lawns during the cooler spring and fall months, spreading by above-ground stems and creating puffy, dense patches that are finely textured.
- Control broadleaf weeds using a post-emergent herbicide, applying the weed killer in early fall for perennial weeds and winter annual weeds like henbit or in spring for summer annual weeds like black medic and knotweed.
- Apply a pre-emergent herbicide two to three weeks before new spring growth to kill the seeds of annual grass weeds. Spot treat perennial grassy weeds using a non-selective herbicide when the weeds are actively growing.
- Don't mistake black medic for clover. Although the two weeds appear quite similar, black medic has smaller flowers and is an annual weed instead of a perennial like clover.