Bromus inermis Seeds | Smooth Brome
LATIN NAME: Bromus inermis
COMMON NAME: Smooth Brome
Plant Profile
Smooth brome is a rhizomatous perennial grass of the family Poaceae, native to Europe and temperate Asia and planted across North America since the 1880s. It grows sixty to a hundred and twenty centimetres, with smooth, broad blades and an open, nodding panicle that droops to one side when the seed is ripe.
It spreads by long, pale rhizomes that travel through the topsoil and produce a uniform sward, and it is one of the few grasses that will hold a shady bank under trees. The whole plant is almost hairless, which is what separates it from the other bromes, and it carries no awns.
Science & Biotechnology
Smooth brome was brought to North America as a hay grass, and by the 1940s it had been selected into cultivars such as Lincoln, bred for the northern prairies. It is now one of the most widespread introduced grasses of the continent, and it is treated as an invader in the remnants of native tallgrass prairie.
The mechanism is partly chemical and partly structural. Its litter builds a thick thatch that keeps light from native seedlings, and root exudates have been shown to suppress the growth of some prairie species. Nitrogen addition makes it more competitive, so its spread is tied to fertiliser drift and to the suppression of fire. Restoration projects now routinely treat established stands with repeated mowing or herbicide before reseeding with natives.
Uses & Benefits
It remains a productive hay and pasture grass, particularly on the northern plains, where it yields well in cool seasons and recovers quickly after cutting. It is also used for erosion control on roadsides, on mine spoil and on streambanks, where the rhizome mat holds soil that would otherwise wash.
For a garden it is a useful grass for a shady place where a lawn will not grow, and for the edge of a pond or a wild corner. It should not be sown near a prairie remnant or a wild meadow, and in North America the guidance is to keep it out of restoration seed mixes altogether, since it will dominate them within a few years.
Growing from Seed
Sow in spring or late summer at ten to fifteen kilograms per hectare, or three grams per square metre for a patch, into a firm seedbed at a depth of one centimetre. Seedlings appear in ten to fourteen days at 15-20 °C. The seed is short-lived, so use the current season’s crop.
Water the sowing until the seedlings are established, and expect the rhizomes to begin spreading in the second year. To hold it in check, cut it twice a season before the seed ripens and remove the cuttings, since the litter is half the problem. In a lawn it needs regular mowing to stay dense, and it will thin in a dry summer without irrigation.
Our Take
A productive hay grass and a stubborn invader, depending on which side of the fence you are on. Sow it for shade and erosion, never near a wild meadow.
Related Reading
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