Montana Field Guide

PLANTS: Cool season, bunched, perennial grass, 10-30 cm tall. Plants have a large showy, dark panicle which greatly exceeds the cauline leaves at reproductive maturity.

LEAVES: Basal and cauline alike, generally 5 to 10 mm wide. The 4-7 cauline leaves have a hairy ligule, 2-6 mm long. Fall shoots arising from all but the upper nodes. Vegetative leaves can form rosettes.

INFLORESCENCE: A diffuse, open panicle. The panicle may appear dark due to the second glume becoming purplish at maturity. Spikelets 1.5–2 mm long with 1 fertile floret. Glumes hairy and unequal in length. First glume 0.5–0.75 mm long and second glume 1.5–2 mm long. Lemmas are blunt, globe-like. Palea is enclosed in the floret.

Montana plants are subspecies sericeum (Lesica et al. 2012).

Sources: Lesica et al. 2012; Freckman & Lelong in FNA 2007; Flora of the Great Plains (1986).

Dichanthelium has been segregated from Panicum. Montana has 3 species of Dichanthelium. Members of Dichanthelium:
* Develop a rosette of short, broad basal leaves during the cool season, while Panicum species do not.
* Grow during the cool and warm seasons, whereas, Panicum species grow in the warm season.
* Produce cleistogamous (self-pollinating) florets, which are often found on small axillary inflorescences during the late summer to fall.

Panic Grass – Dichanthelium acuminatum subsp. sericeum, native, SOC
* Stems 10-30 cm tall.
* Spikelets 1.5-2.5 mm long.
* At maturity the larger second glume is often purplish.
* Upper and lower leaf surfaces hairy.
* Ligules 2-6 tall.
* Often in wet soils around hot springs.

Wilcox’s Panic Grass – Dichanthelium wilcoxianum, native
* Stems 10-20 cm tall.
* Spikelets less than 2.5 mm long.
* Upper and lower leaf surfaces hairy.
* Ligules 1.0 mm or less tall.
* Grasslands and open Ponderosa Pine forests in eastern Montana.

Scribner’s Panic Grass – Dichanthelium oligosanthes var. scribnerianum, native, SOC
* Stems 20-50 cm tall.
* Spikelets 2-5 mm long.
* Upper leaf surface is glabrous. Lower leaf surface is hairy.
* Ligules 1-3 mm tall.
* Disturbed sites and open understory in northwest and southeast Montana.


Switchgrass (Pancium virgatum) is a rhizomatous, perennial grass while Montana's other Panicum species are annuals.

Often forming dense stands on wet soils around edges of hot springs (Lesica et al. 2012).

This grass can produce panicles in both the late spring to early summer and the mid-summer to fall periods (Lesica et al. 2012; Flora of the Great Plains 1986). Early flowering plants may exhibit both self-pollinating and cross-pollinating florets. Late flowering plants may have panicle branches clustered among the leaves and are composed of self-pollinating florets.

STATE THREAT SCORE REASON
Reported threats to Montana's populations of Tapered Rosette Grass (Dichanthelium acuminatum subsp. sericeum) are currently assigned as unknown. Potential threats of ground disturbance and recreation need to be substantiated before a threat rank can be assigned (MTNHP Threat Assessment 2021).