Ripgut Brome (Bromus diandrus)

Ripgut brome (Bromus diandrus) is a very common invasive grass that has established itself in our region's grasslands. Anyone walking through a meadow in the summer is probably familiar with this invasive plant as, following said walk, you've probably spent a few minutes picking its seeds out of your socks.

Ripgut brome is named for its spikey barbs that hook onto clothes, fur, and, as the name suggests, the stomach linings of herbivores. European livestock animals like goats, sheep, and cattle evolved with the grass so they are somewhat adapted to graze it, but our native herbivores like rabbits and deer are less equipped to graze on it. Therefore, ripgut brome can, for the most part, grow unmolested and dominate grasslands.

Ripgut brome is an annual grass, meaning it grows quickly following rain, drops its seeds, and then dries out and dies shortly thereafter. It also grows in dense patches and crowds out native grasses. This contributes to increased fire load when compared to our native grasslands.

This invasive grass often displaces purple needlegrass - our native equivalent (and California's official state grass). In comparison, purple needlegrass has smooth (non-barbed) seeds which don't irritate herbivores' stomachs. It grows in bunches, rather than uniform mats, so it allows for open ground between plants which provide opportunities for birds like black pheobes to land and grab insects or for hawks to swoop in and grab a rodent that was foraging for seeds. Purple needlegrass is also a perennial plant, meaning it lives year-round, which means it stays green longer and stores water during the summer. As a perennial bunchgrass, it presents a significantly lower fire hazard when compared to ripgut brome dominated grasslands.

Ripgut brome is difficult to control, but can be done through maintained grazing from livestock. As an annual grass, ripgut brome cannot easily regenerate from its root after being munched by herbivores, but purple needlegrass, as a perennial plant, stores most of its nutrients in its roots and can withstand and regrow after light grazing.