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Weed Identification

Virginia Tech College of Agriculture and Life Science Virginia Cooperative Extension

wild oat

Family

Poaceae

Scientific Name

Avena fatua
Weed photograph 1
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Weed photograph 11

Other Common Names:

wheat oats
oatgrass
flaxgrass

Habit

Moist conditions promote germination which occurs primarily in spring. Tillers are produced 2-4 weeks after emergence. Seeds fall to the ground as they ripen, usually before crop harvest.

Leaves

Seedling: Leaves are rolled in the bud. Auricles are absent, and ligules are membraneous, large, whitish, and pointed. Leaves may be smooth or hairy. Hairs, when present, are both small and large; larger hairs are sparse. Mature Plant: Leaves are rolled in bud, and auricles are absent. Ligules (2-6 mm long) are membraneous, rounded, and torn at the top (lacerate). Blades are linear, not keeled (3-16in long and up to 3/4in wide), rough to the touch, and taper to a pointed tip. Blades are often hairy near the ligule and on the margins near the base. Sheaths are compressed and vary from smooth to occasionally sparsely hairy. Collars are sparsely hairy at the edges. Stems are smooth and erect.

Identifying Characteristics

Auricles are absent and ligules are large membraneous and torn at the top. Seed are larger than most grasses and have long awns.

Flower Seed Head

Flowers from July to September. Spikelets are in a loose, open drooping, pannicle (6-16in long and up to 8 in wide). Spikelets are nodding, and the florets (up to 1 1/2in long) have a twisted, angled, dorsal awn (1 to 1 1/2 in long) that straightens and twists with changes in humidity.

Seed Fruit

Seed are up to 1 1/2in long and have an additional 1 to 1 1/2in long awn that twists and turns with changes in humidity. This twisting motion tends to bury seeds after they fall to the ground. A single plant can produce 100-150 seeds.

Where Found

Wild oat is a weed of agronomic crops, especially spring cereals, as well as of vegetables, nursery crops, and landscapes. Found on heavy clay and clay-loam soils, it prefers cool climates and moist soil and often grows on the lower, moister regions of agricultural fields.

Leaf Hair on Upper Surface

Varies: 
no hairs, 
hairs from base to tip

Leaf Arrangement

rolled in bud

Mature Leaf Width

Varies: 
less than 5 mm, 
6 to 15 mm, 
more than 15 mm

Stem

flat or oval

Seedhead

Varies: 
branched spike, 
panicle

Root Structure

fibrous

Life Cycle

winter annual

Auricle

not present

Ligule

membrane

Ligule Length

more than 3 mm

Plant Type

Grass