Trailing Grama Grass (Bouteloua diversispicula) in Arizona: Recent Learnings
Posted Aug 09, 2022
Contributed by John Scheuring, AZNPS State Conservation Committee Chairman aznpsconservation@yahoo.com
Trailing Grama is a perennial native grass that in wet summers forms prolific stolons that knit desert soils together in shallow rooted turf-like stands. Tom van Devender’s 2020 Plant Press article describes Trailing Grama as a “keystone species” that binds soil together in fragile desert areas and underpins the growth of other desert native grasses and forbs. Unfortunately, vast Trailing Grama mixed desert grasslands in Sonora have been ripped and planted to buffelgrass over the years.
Here in Arizona on Ironwood Forest National Monument, Trailing Grama has been long established on RaggedTop, Silverbell Peak and three adjacent foothill areas. Those plants grow side-by-side Bouteloua repens, Muhlenbergia porteri, Tridens muticus, and various Aristida species.
In 2020, AZNPS roadside buffelgrass control volunteers discovered Trailing Grama growing in the right-of-way of Oracle Rd/US77 on the northern edge of Oro Valley. In 2016 ADOT contracted the hydroseeding of the right-of-ways along the newly widened Oracle Road. The hydroseed contractor had sourced most of the grass seed in Sonora and the Trailing Grama was probably mixed with other native seeds. As soon as the Oracle Road plants were discovered, they were sent to the UA herbarium to verify their Bouteloua diversispicula identity.
With the very wet 2021 and 2022 monsoons in NW Tucson, the Trailing grama has spread 6 miles along Oracle Road and one mile along Tangerine Rd.
The spread is evidenced as little toeholds on the edge of the pavement followed by spread of plantlet and runners (stolons) growing down the slopes and the roadway runoff gradient. The Trailing Grama plants opportunistically fill in empty spaces especially in the wetter areas near the pavement edges. The spread stops when there is insufficient residual moisture to support it. The plants knit the soil together and provide ideal resistance to soil erosion.
The really good news is that this year for the first time there is clear evidence that Trailing Grama is outcompeting Bermudagrass along moist roadsides.
Trailing Grama holds tremendous potential for roadside erosion control and urban landscaping. There is a lot to learn.
One-gallon pots of Trailing Grama can be purchased at Desert Survivors Native Plant Nursery, 1020 W Starr Pass Blvd, Tucson, AZ 85713.
