Rolland's bulrush - Trichophorum pumilum
Other Names:
Scirpus pumilus, Scirpus rollandii
State Rank Reason (see State Rank above)
DRAFT: Requesting feedback on the 2026 revised rank, factors, and State Rank Reason outlined below and in the Conservation Status Rank Report.
Trichophorum pumilum is rare in Montana, where it is known from approximately 8 populations along the Rocky Mountain Front. Several of these sites occur on lands managed for their conservation value. No significant and widespread threats to the species are known, besides potential impacts associated with climate change. However, changes in hydrology from water use and diversion have the potential to negatively impact some populations. Population levels are imprecisely known, though at least several occurrences appear to consist of large populations. Trends are unknown though populations have likely been relatively stable in the recent past or experienced only minor declines.
Climate change may negatively affect this species over the next several decades. However, the timing and magnitude of potential impacts are largely unknown. Although climate change is listed as a potential threat to the species, it does not affect the overall threat rank or scoring, or the final subnational rank.
Survey and monitoring data are needed to be able to more precisely determine population levels, assess condition and for assessing population trends. Surveys in potentially suitable habitat may document additional occurrences.
Caespitose. Stems terete, 5–25 cm, clustered on thin rhizomes. Leaf blades ca. 0.5 mm wide. Spikelet 3–4 mm long with 3 to 6 flowers; awn of lowest bract shorter than the spikelet. Scales 2.5–3.5 mm long, glabrous, brown with a pale midstripe; tip rounded. Flowers: bristles absent. Achene 1.5–2 mm long (
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Fruiting in July.
After mid-summer,
Trichophorum pumilum looks like a tiny stick with a few little black eggs glued on top. It is most likely confused with species of
Eleocharis, but in these species, the base of the style is enlarged, and the scales are persistent.
Trichophorum cespitosum is a larger plant that forms distinctive tussocks. A hand lens will be necessary for positive identification.
In botanical keys,
Trichophorum pumilum and
Amphiscirpus nevadensis may key closely.
Rolland's Bulrush -
Trichophorum pumilum, Native, SOC
*Perianth Bristles: 0; absent.
*Achene: Tipped with a skinny, short beak (style). Subtended by a scale.
*Scales: Apiculate.
*Spikelets: Solitary, 3-7 mm long. Spikelet is not subtended by a leaf-like bract.
*Stems: Round, less than 15 cm tall.
*Leaves: Less than 0.5 mm wide.
*Habitat: Hummocks in calcareous fens.
Nevada Clubrush -
Amphiscirpus nevadensis, Native, SOC
*Perianth Bristles: 1-6, inconspicuous and shorter than the achene.
*Achene: Not tipped with a beak; style absent. Subtended by a scale.
*Scales: Awn absent.
*Spikelets: Solitary, but usually some plants have at least 2 spikelets; 6-12 mm long. Always with 1 long, leaf-like bract below (subtended) the spikelets.
*Stems: Round, wiry, and erect. Lacks internal cavities.
*Leaves: Basal and on lower stem, 0.5-2.0 mm wide.
*Habitat: Moist to wet alkaline wetlands, but not aquatic.
Calcareous fens in the foothills.
