Northern Illinois Weeds

dandelion

 Dandelion

Weed Type: Perennial broad-leaf

Problem Areas: Invades thin lawns and most other places. Prefers sun but otherwise tolerant of a wide range of conditions.

Identification: Dandelions leaves form a low rosette. Leaves are deeply lobed with the tips of the lobes pointing back toward the center of the plant. Flowers are held singly above the leaves, up to 2” wide, and have many yellow petals. Flower stalk is hollow. Seed cluster is a small puffball. Spreads by seed. Taproot allows plant to regrow but it does not naturally spread in this way. However, if pieces of taproot are spread around a garden area by cultivation, each will produce a new plant. Correct mowing height and adequate fertilization will help lawn out-compete dandelions. Best control methods.

crabgrass

Crabgrass

Weed Type: Annual grass
Problem Areas: Common invaders of thin lawns especially those mown too short or given light, frequent irrigation. May also be found in garden beds.

Identification: Grows in clump; leaves light green; nodes swollen and stem zigzag; prostrate habit and may root at lower nodes. Both species have membranous ligules and no auricles. Large crabgrass has hairs on sheath and blade; smooth crabgrass has a few hairs on blade just above collar. No stolons or rhizomes. Best control methods.

white clover

White clover

Weed Type: Perennial broadleaf

Problem Areas: Invades lawns, especially those growing in soil low in nitrogen or over-fertilized with potassium. Tolerates low mowing but doesn’t compete well with taller plants.

Identification: Short plant, about 6”, with alternate leaves with three leaflets. Each leaflet may have a faint, white
crescent or “v” shaped mark. White flowers are held in a rounded cluster, about ¾” across, occurring sporadically through the summer. Spreads by stolons and by seed. Fertilization to encourage grass growth will help lawns compete against clover. Larger plant with similarly marked leaves but pink flowers is red clover. Best control methods.

 
Ground ivy

Ground ivy (Glechoma hederacea)

Weed Type: Perennial broadleaf
Problem Areas: Invades lawns and landscapes, prefers moist, fertile, shady sites but can tolerate full sun
Identification: Leaves opposite on long petioles. Leaves kidney shaped, almost encircling petiole, about an inch wide, edges are scalloped. Leaves have a mint scent when crushed. Purple flowers in May but they may not be noticed. Ground ivy forms long slender stolons that root at the nodes. Plant is an aggressive spreader and difficult to control. Best control methods.

Violets

Violets

Weed Type: Perennial broadleaf
Problem Areas: Invades moist, shady, fertile sites including lawns, which often grow poorly in shade
Identification: Violet leaves form a rounded clump about 5” high. Leaves are heart-shaped and waxy, with a long petiole, the blade often cupping toward the petiole. Flowers blue to violet to white in May, asymmetrical with 5 petals. Forms rhizomes and spreads. Hand digging can be effective if rhizomes are thoroughly removed. Best control methods.

Spotted spurge

Spotted spurge (Euphorbia maculata)

Weed Type: Annual broadleaf
Problem Areas: Invades lawns and landscapes with dry, nutrient-poor soils. It competes well with lawn grass that is mowed too  short.
Identification: Spotted Spurge is a summer annual that can create a mat of stems more than a foot wide. Stems hug the ground and radiate from a  central point. All parts release a milky sap when broken (common characteristic of many Euphorbia species). Leaves are waxy, succulent, opposite, and oblong, <1”, often with a maroon mark in the center of the leaf (the “spot” in the common name). Flowers are inconspicuous, pink, and found in the leaf axils. Forms a short taproot. Prostrate spurge (Euphorbia humistrata) is similar but it will root at the nodes. Best control methods.

Canada thistle

Canada thistle (Cirsium arvense)

Weed Type: Perennial broadleaf
Problem Areas: Invades just about anywhere
Identification: Canada thistle is a perennial broadleaved weed with creeping roots that extend up to 17 feet (5 m) horizontally and 20 feet (6 m) deep. Plants grow 2 to 5 feet (0.6 to 1.5 m) high. The stem is slightly hairy when young and grows hairier with age. Leaves are alternate and oblong. They have irregularly lobed margins with spiny crinkled edges terminating in a spine. The upper side of the leaf is dark green; the lower side is light green and slightly hairy. Some plants have leaves that are smooth on both sides. Canada thistle leaves are stalkless. The base of each leaf surrounds the stem, giving the impression that the stem is also spiny. Best control methods.

Prostrate knotweed

Prostrate knotweed (Polygonum aviculare)

Weed Type: Annual broadleaf
Problem Areas: Invades areas with compacted soil such as paths and play areas.
Identification: Prostate knotweed is a summer annual that forms a broad, low, tough mat.  Stems radiate from a central point, up to 24” long. Begins growth early in season. Leaves are alternate, elongated, and without teeth, about 1”.  A thin membranous sheath circles the stem at the leaf  base. Flowers are white to pink and inconspicuous. Best control methods.

Purslane

Purslane (Portulaca oleracea)

Weed Type: Annual broadleaf
Problem Areas: Invades areas with bare soil and also those with mulch, common in newly seeded areas where other plants are not well established, prefers areas in full sun. Tolerant of poor, compacted, droughty soils.
Identification: Purslane is a mat-forming summer annual that grows low to the ground. Leaves are succulent, opposite, oval, waxy, and without  teeth. Stems are succulent and red. Flowers are yellow and small, in summer. Has a thick, fleshy taproot. Broken stem segments left  on soil will root and resume growth. This species is sometimes cultivated as an ornamental annual. Best control methods.

Yellow nutsedge

Yellow nutsedge (Cyperus esculentus)

Weed Type: Perennial monocot
Problem Areas: Invades lawns and landscape beds, especially those with moist to wet soils. Underground structures can lie dormant  for 10 years or more waiting for favorable conditions.
Identification: Perennial sedge with a triangular stem, usually much more yellow than lawn grass and faster growing. Flowers and  seeds are held in clusters of short spikes. Forms underground structures, small and round, called nutlets. Yellow nutsedge is very difficult to control with cultivation. Best control methods.

Foxtails

Foxtails (Setaria species)

Weed Type: Annual grass
Problem Areas: Found in thin lawns or bare garden areas
Identification: There are three common foxtail species, all with thin elongated flower clusters (like a fox’s tail). Green foxtail has  hairy ligules but otherwise leaf has few hairs (may be rough to touch). Yellow foxtail has hairy ligules and long hairs on the upper  surface of leaves, usually near the collar region. Leaves may have a spiral twist. Giant foxtail has hairy ligules and the upper surface  of the blade is covered with short hairs. Best control methods.

Quackgrass

Quackgrass (Elymus repens)

Weed Type: Perennial grass
Problem Areas: Quakegrass invades lawns, crops and landscapes. May be brought in with topsoil. Rhizomes can survive cultivation
Identification: Cool season grass with long rhizomes. Leaves have very short ligule but long, clasping auricles. Best control methods.

Creeping bentgrass

Creeping bentgrass (Agrostis stolonifera)

Weed Type: Perennial grass
Problem Areas: Used on golf courses. Home lawns nearby may be invaded. Bentgrass seed has sometimes been included with lawn grass seed. May be a contaminant in low-quality bluegrass seed mixtures. Will be more of a problem in lawns with good irrigation.  Can tolerate very low mowing.
Identification: Cool season grass that spreads by stolons. Usually lighter or more blue green than lawn grasses with a much finer  texture. No auricles. Ligules are long and membranous. Leaves are ridged but not hairy. May be confused with nimblewill (ligules  different) or Bermudagrass (which has rhizomes). Best control methods.

Zoysiagrass Royal Gardens Landscaping

Zoysiagrass (Zoysia japonica)

Weed Type: Perennial grass
Problem Areas: Warm-season lawn grass sometimes grown in southern Indiana that becomes a weed when growing in lawns of cool  season grasses

Identification: Spreads by stolons and rhizomes, will turn brown in cool weather, green up in summer. No auricle. Ligule hairy, collar region with many long hairs. Upper leaf surface may also have long hairs. May be confused with Bermuda grass which also has rhizomes. Zoysiahas hairs standing upright on the blades.grass. Best control methods. 

bindweed

Bindweed 

(Convolvulaceae)

Weed Type: Perennial vine

Problem Areas: Invades thin lawns and most other places. Prefers sun but otherwise tolerant of a wide range of conditions.

Identification: is a species of bindweed in the morning glory family (Convolvulaceae), native to Europe and Asia. It is a climbing or creeping herbaceous perennial plant growing to 0.5–2 m high. The leaves are spirally arranged, linear to arrowhead-shaped, 2–5 cm long and alternate, with a 1–3 cm petiole. The flowers are trumpet-shaped, 1-2.5 cm diameter, white or pale pink, with five slightly darker pink radial stripes. Flowering occurs in the mid-summer, when white to pale pink, funnel-shaped flowers develop. Flowers are approximately 0.75-1 in. (1.9-2.5 cm) across and are subtended by small bracts. Fruit are light brown, rounded and 1/8 in. (0.3 cm) wide. Each fruit contains 2 seeds that are eaten by birds and can remain viable in the soil for decades. Best control methods.