Weed Seed: Silky bent-grass (Apera spica-venti)

Family

Poaceae

Synonyms

Agrostis spica-venti

Distribution in Canada

Found in ON

Duration of life cycle

Winter annual

Seed/Fruit type

Grain, enclosed by palea and lemma

Seed identification features

Size

• floret length: 3.0–3.7 mm
• awn length: 4.0–7.0 mm
• width: 0.5 mm

Shape

• in outline: elongated oval
• in cross-section: elliptical

Surface texture

• roughened, pebbled surface, like sandpaper
• short, stiff hairs on back of lemma, from middle to tip

Colour

• medium brown

Other structures

• long, thin awn extends straight from tip
• short, thin stalk (rachilla) on inner base of seed
• tuft of long, white bristles at base of outer side (lemma)
• grain is soft (will yield under pressure)

Similar species

Interrupted bent-grass (Apera interrupta)

• found in BC, ON, and the northwestern United States
• similar to silky bent-grass in shape, awn, tuft of hairs at base, roughened surface texture and short hairs at top of lemma
• floret longer than silky bent-grass by 1.0–2.0 mm, with an awn up to 7.0 mm longer

Velvet bent-grass (Agrostis canina)

• found in QC, NB, NS, PE, NL, and the northeastern United States
• similar to silky bent-grass in shape, size, awn and rachilla
• Longer than silky bent-grass by 1.0–2.0 mm
• awn is not bent, surface is smooth, and colour is darker than silky bent-grass

Species Comparison Chart

Species	Length	Awn length	Surface texture
silky bent-grass	3.0–3.7 mm	4.0–7.0 mm	roughened
interrupted bent-grass	4.0–5.0 mm	4.0–14.0 mm	roughened
velvet bent-grass	4.0–5.0 mm	1.0–3.0 mm	smooth

Photos

Similar species