Community Agriculture Alliance: Bulbous bluegrass bulldozing its way into the Yampa Valley |

Community Agriculture Alliance: Bulbous bluegrass bulldozing its way into the Yampa Valley

Tiffany Carlson
For Steamboat Pilot & Today

Bulbous bluegrass (Poa bulbosa L.) is the newest invasive grass species to attack unknowing residents in the Yampa Valley.

Following quickly on the heels of Cheatgrass (Bromus tectorum), Bulbous bluegrass has shown significant encroachment into Routt County within the last decade and has demonstrated an extreme increase in the last three years. The Routt County Noxious Weed Program has been fielding an increasing number of inquiries from concerned residents wanting information on how to best tackle this weed. 

Noxious grasses can be a challenge to identify, being that they lack the showy eye-catching flowers that many other noxious forbs have. Bulbous bluegrass is thought to have been introduced from Eurasia and is spread easily by a number of vectors, primarily contaminated hay and hay equipment in our area. It even used to be used as a species to aid in restoration, having been used to seed eroded areas where rapid establishment was needed.

Bulbous bluegrass is a perennial bunchgrass that grows 8-24 inches tall. This species reproduces from bulbets, which sprout from the parent plant and from basal bulbs. This is one of the early grasses to green in the spring and produces mature seed heads as early as May when other perennial grasses are just starting to emerge. 

One of the most concerning facets of bulbous bluegrass is that bulbets do not require dormancy or stratification; they can start growing immediately upon making contact with the soil. This immediate and early season growth gives this species a serious advantage over many of our native and perennial grasses.

Bulbous bluegrass plants can be consumed by wildlife and livestock in early spring until they flower. Early heavy grazing for several growing seasons can be used as a cultural control to reduce productivity and spread of bulbets but has little effect at reducing an infestation size. If you detect this species early, small infestations can easily be pulled up as their root system is relatively shallow. Be sure to securely bag or burn plants that are mechanically controlled. 

There are some chemical control methods, but these pose their own challenges for desired results. Glyphosate can be utilized; however, it is a nonselective herbicide and timing is critical.

This herbicide must be applied very early to actively growing bulbous bluegrass before other perennial grasses emerge; otherwise you will be left with bareground. Studies are currently being done utilizing indaziflam and imazapic, which incorporates both a pre- and post-emergent control.

However, established perennials must be in the area, or again, you are going to have bareground. Leaving bareground in any situation poses many environmental concerns and will be an invite for further noxious weed establishment. Reseeding of any treated area should be seriously considered with regard to replanting intervals and depths for specific herbicides utilized. 

As with all noxious weed species, early detection and rapid response is the most time- and cost-effective approach. Please be on the lookout for this weed! 

For assistance with identification or management of bulbous bluegrass or other noxious weeds, please contact with the Routt County Noxious Weed Program. 

Tiffany Carlson is the Noxious Weed Supervisor for Routt County

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