How to Manage Pests

Identification: Weed Photo Gallery

Quackgrass

Scientific name: Elytrigia repens (Grass Family: Poaceae)

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Quackgrass, a perennial grass, is a B-rated noxious weed in California. It is found throughout California, except deserts, up to 5900 feet (about 1800 m), but is primarily found in northern and coastal regions. Quackgrass inhabits moist meadows and disturbed sites. Found abundantly in mountain meadows, it thrives on different soil types, in gravel and peat, and also under saline and alkaline conditions. It is a highly competitive agricultural weed and can significantly reduce crop yields and contaminate seed grain crops. Cultivation and herbicide applications may need to be repeated to eliminate quackgrass problems. Avoid spreading or reintroducing quackgrass on contaminated equipment or in irrigation water.

Habitat

Moist meadows, cultivated fields, urban landscapes, and other disturbed sites.

Seedling

Leaf characteristics are similar to those of mature plants, except that blades are usually narrower and auricles may not be developed. By the six- to eight-leaf stage, underground, horizontal stems (rhizomes) develop.

Young plant

Plants that sprout from belowground horizontal stem (rhizome) buds form their own rhizomes at the three-to-four-leaf stage.

Mature plant

Quackgrass is erect, can form clumps, and grows to almost 4 feet (1.2 m) tall. Stems are round in cross-section and stem joints (nodes) appear swollen. Leaves are rolled in the bud. Leaves are flat, about 1-3/5 to 12 inches (4–30 cm) long and 4/5 to 5-1/2 inches (2–14 mm) wide, droop, and are often constricted at the tip. The lower leaf surface has a waxy coating, and the upper leaf surface has either a hairy or waxy coating. The sheath is open, hairless or covered with short, soft hairs. The ligule is membraneous with a fine fringe. Auricles are narrow, clasp the stem, and tinged whitish to violet.

Collar region

The sheath is open, hairless or covered with short, soft hairs and the ligule is membraneous with a fine fringe. Auricles are narrow, clasp the stem, and tinged whitish to violet.

Flower

Flowering takes place from May through September. The flower head is a spike about 2 to 8 inches (5–20 cm) long. The spikelets are flattened, stalkless, and alternate to one another along the spike.

Seeds

Seeds are formed in flattened spikelets along the seed head.

Reproduction

Reproduce by seeds and underground, horizontal creeping stems (rhizomes). Rhizomes have been observed penetrating hard soils and growing into potato tubers. Rhizomes are easily spread during cultivation or harvesting and fragments on equipment will also spread this weed to other fields. They occur mostly in the upper 6 inches (15 cm) of soil and may reach depths of 8 inches (20 cm), spreading laterally 3 to 5 feet (0.9–1.5 m).

More information

• Grass ID illustration
• Calflora's distribution map
• See UC IPM's Pest Management Guidelines for agricultural information