By Ellen Dean
The Rare Plant of the Month blog highlights one of the rare plants in the CNPS Rare Plant Inventory (RPI), an invaluable resource that has helped protect approximately 2,450 rare plant taxa in California since 1974!
Have you seen bullgrass (Muhlenbergia emersleyi) in the wild? This California Rare Plant Rank 2B.2 plant (rare, threatened, or endangered in California but more common elsewhere) is known from just two occurrences in the state. It’s been seen in the Santa Rosa and San Jacinto mountains of Riverside County, but outside of California it is more widespread to the west (in Arizona and New Mexico), as well as to the south in Mexico, including Baja California. The California occurrences are somewhat disjunct (far) from populations in Arizona and Baja California, but they are a continuation of a mountainous distribution that runs along the spine of Baja. Bullgrass grows in montane chaparral in moist, rocky soil, sometimes along washes.
This beautiful bunchgrass is difficult to miss—it can grow to 5 ft tall! Bullgrass was first encountered by western scientists when southern California botanists Tom Chester and Keir Morse encountered it; Morse then identified the plant as Muhlenbergia emersleyi in 2016. It was added to the CNPS Rare Plant Inventory in 2019, and Morse and grass expert Paul Peterson added it the Jepson eFlora in 2023.
Muhlenbergia is a genus of plants in the grass family that may bear a passing resemblance to Cousin Itt from The Addams Family. Gardeners will be most familiar with deergrass (Muhlenbergia rigens). (Despite these two examples, not all Muhlenbergia are named for animals.) Botanist Scott White revisited bullgrass recently along the Pacific Crest Trail in the Garner River watershed in the San Jacinto Mountains. It flowers and fruits September through November after summer monsoon rains, which may not occur every year. This late-blooming habit may be the reason for its late discovery by botanists in California. Many people explore southern California habitats after winter or spring rains, and they are less likely to botanize in the fall. No threats have been noted for this species except that it has relatively small population sizes, which could die out due to climate change or other disturbances. If you’re attending the CNPS 2026 Conference in Riverside, you might want to take a side trip to visit the remaining locations in California of Muhlenbergia emersleyi. Learn more about bullgrass in the CNPS Rare Plant Inventory.
Ellen Dean is Associate Rare Plant Botanist at CNPS, helping complete rare plant profiles. In a previous life, she was an herbarium botanist, performing plant IDs, leading collecting field trips, training students in plant identification, curating the herbarium, and publishing taxonomic papers.
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