It’s that grass whose seeds get caught in your shoes and socks when you go hiking, cheatgrass (aka. Downy brome Bromus tectorum, Japanese brome Bromus japonicus) is a winter annual List C noxious weed in Colorado. Originating in Europe, it grows on the decaying straw thatched roofs in the Mediterranean region. This is how it got its name; “tectum” is Latin for roof, so “brome of the roof.” It got its common name, cheatgrass, because it germinates early, some years in August or September, over winters and is taking up moisture and nutrients early in the spring before most other plants are actively growing.
Being an annual, it only reproduces by seed. Not all the seeds germinate the year they are produced. Some seed survives in the soil for up to 5 years. Cheatgrass plants mature and produce seed by June. Infested areas can have 600 to 1200 plants that produce approximately 1600 seeds per square foot or 478 per acre. Cheatgrass seedlings are identified from other grasses by being one of the first grasses up and growing each year. They are very soft hairy seedlings with a reddish tinge during the winter.
Cheatgrass has altered our wildfire regimes. Because it matures so early in the year, it is tinder dry during the hot summer months and readily and intensively burns. Historically, wildfires occurred approximately every 30 years in the foothills, but this timing has been reduced to approximately every three years in cheatgrass infested areas. Cheatgrass also changes the nitrogen distribution in the soil profile. It is a nitrogen user, so it uses the nitrogen in the upper profile causing a nitrogen deficiency. Over fertilizing early can favor cheatgrass growth.
The management key is keeping it from going to seed by grazing, mowing or pulling and being persistent!
If you have grazing livestock and poultry, cheatgrass is good forage early on before the flower and seed head come out. If you can over graze the cheatgrass without overgrazing your desired grass/es, you stress the cheatgrass and make it easier to manage.
If you are mowing, mow high the first time so when it produces a second flower/seed head you have height to be able to mow lower the second time. If you mow it to the ground the first time, it may set its second flower/seed head lower than you can mow. Set your mower to cut just below the seed head.
If you are ambitious, you can pull the plants. With a little moisture, they easily pull out of the ground. If they have not gone to seed, you can compost them. If they have flowers or mature seeds, you need to dispose of them in the trash. Once the heads come out, you do not want to continue grazing. The seed with the awn can get lodged in an animal’s mouth or eyes causing sores and ulcerations or in fleece lowering its value.
Because it is a grass, trying to manage it growing among other grasses and forbs is hard. For the urban dweller, hand pulling is feasible. For those with larger lots and acreages, you need to at a minimum mow to prevent or lower seed production or consider using an herbicide. Management is best done when the plants are small. Don’t wait until it is producing seed to start managing it. Organic herbicides can be used when the plants are small. Organic herbicides are non-selective so they will damage or kill desired plants too so they must be used with care. There are synthetic herbicides that can be used to manage cheatgrass. Care must be taken to choose the correct herbicide and use it according to the label.
By Sharon Bokan, Colorado State University Extension Boulder County