Bromus Commutatus found in Teton County

Published: 2019
By Mat Walter

Teton county received over 100 plants and insects for diagnostics in the spring of 2019. Of those samples, one stood out among the others, Bromus commutatus, (Meadow Brome, Hairy Chess, Hairy Brome). Bromus commutatus is a warm season annual grass that is rarely found around Montana. In recent years, receiving an unknown grass sample in the office has led to some stress and certain fears as to its identification. With invasive grasses such as Ventenata dubia (Ventenata), and Taeniatherum caput-medusae (Medusahead) slowly making their way into Montana, any unknown grass-species has the potential to have a profound effect on the local ecology. Lucky for Teton county, Bromus commutatus is a relatively benign plant; with a structure and look that is relative to most brome species such as Bromus tectorum (Cheatgrass) and Bromus japonicas (Japanese Brome), the key difference is in the plant size. Meadow Brome, is considerably taller (33+ inches) and appears less dense than these other species. The plant sports closed hairy sheaths that are similar to Japanese Brome but not as hairy, the inflorescence is also similar to Japanese Brome. Therefore, if you ever come across plants that appear to be two to three times the size of Japanese Brome, it is highly likely you are looking at a Meadow Brome. Currently the plant poses no risk to Montana rangelands, however while uncommon, it is still important to keep an eye out for plants that appear out of place in our landscape.