Grasses of the Eloise Butler Wildflower Garden

Smooth Brome is a perennial introduced grass with stems (culms) that are single or a few together, growing 1.5 to 4 feet high. Nodes number 3 to 5. Stems and nodes are usually without hair.

Leaves: Leaves are both basal and stem, flat, to 15 mm wide (5/8 inch), 4 to 14 inches long, numerous and frequently marked by a wrinkle like a "W" a short distance below the tip.

Sheath throats and collars are usually without hair; The ligule is often brownish at the base, truncate, and the collar is hairless and light or yellowish green. Auricles are sometimes present. Sheaths are split.

The inflorescence is a panicle, 4 to 8 inches long, of open shape and erect with ascending branches. It colors to purplish brown when mature.

Flowers & spikelets: Spikelets are 20 to 40 mm long, somewhat elliptic to lanceolate in shape with 8 to 10 florets. Spikelets may be purplish prior to maturity but are purplish-brown at maturity. Both lower and upper glumes are veined (1 vein usually on the lower and 3 on the upper), the upper glume longer (7 to 10 mm), both without hair. Lemmas are 9 to 13 mm long, also mostly elliptic to lanceolate in shape, rounded over the midvein, smooth, but margins may occasionally have sparse hair. Florets have 2 anthers; awns are usually absent, but if present are straight and to 3 mm long.

CAUTION - Invasive: Smooth Brome is normally used as a forage plant where it can be controlled. It was formerly recommended for wildlife plantings but no longer as it is an aggressive grower and can become invasive. In Minnesota it is one of three grasses listed as an invasive non-native terrestrial plant. To control it the DNR recommends a late Spring burn, which will decrease the population. If chemicals are used, it should first be mowed and then after new growth starts apply gyphosate.

Habitat: Smooth Brome is a leafy, sod-forming, perennial, cool season grass that spreads by rhizomes. It grows in sun and partial shade, tolerant of various soils and mositure conditions - a trait of many invasive plants.

Names:The genus Bromus, is derived from the Greek bromos, referring to oats, as the flowering heads of this genus resemble oats somewhat. The species, inermis, means 'unarmed' or 'without prickles', in this species referring to the usual absence of awns on the florets. The author name for the plant classification, ‘Leyss.’ refers to Friedrich Wilhelm von Leysser (1731-1815), German botanist, author of Flora Halensis of 1761. The genus Leyssera is named after him.

Comparisons: The rhizomatous root system distinguishes this grass from the other two in the Garden. In North America Smooth Brome is similar to two other introduced species. 1) B. riparius, Meadow Bromegrass, but that species is shorter (only 12 to 30 inches) and has awns. 2) It is also similar to B. pumpellianus, the Arctic Brome, but that species usually have hair on the nodes, sheaths and glumes, and has long awns - to 7.5 mm. Neither of those species are found in Minnesota. There are three species of Bromus in the Garden. See bottom of page for an ID key.