Montana Field Guide

Scribner's Panic Grass is a perennial which forms clumps of simple or branched stems that are 1-6 dm tall. The lower leaves are 3-10 cm long and 3-12 mm wide, while the upper leaves are short and relatively broad. Leaves are mostly glabrous, but the sheaths surrounding the stem are glabrous to long-hairy. There is a short fringe of hairs on the leaf where it meets the stem, which is known as a ligule. The flowers are borne on short to long stalks, which are arranged in a conical inflorescence that is 3-8 cm high. Inflorescences of the main stems are larger than those of the branches. Each egg-shaped spikelet has one flower, is ca. 3 mm long, and consists of two glumes enclosing a lemma and a palea that may or may not be hairy.

Spikelets mature in late June and early July.

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.

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.

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.

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.

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

This plant has been documented from southeast and northwest Montana. In Lake County it was collected in sandy pinelands. Two small colonies recently documented in Powder River County occupied Pinus ponderosa/Mahonia repens habitat. Both were at the upper end of draws, with one on the lower south-facing slope of a steep, wooded drainage and the other at the gently sloping upper end near the border between woodland and grassland. Associated species included Agropyron spicatum, Astragalus agrestis, Astragalus americanus, Carex deweyana, Carex sprengelii, Crepis acuminata, Elymus glaucus, Euphorbia glyptosperma, Penstemon gracilis and Poa pratensis. Soils were well-drained, coarse, sandy or gravelly loams.

Scribner's panic grass is a perennial that reproduces strictly by seed. Both vernal (early season) inflorescences and autumnal (late season) inflorescences are produced. The species survives fire, but impacts on population size are unknown. In one locality that had burned, plants emerged earlier and had more stems than those at a nearby unburned site. This species does not exhibit marked population increases in the wake of fire, as does Wilcox' panic grass (Heidel and Dueholm 1995).

Areas of Lake County where this grass occurs are being invaded by knapweed species. Many wooded draws in southeastern Montana are being invaded by leafy spurge. This panic grass is thought to decrease under grazing (Smith 1976), and overgrazing could adversely affect it.

STATE THREAT SCORE REASON
Reported threats to Montana's populations of Scribner's Panic Grass are those that have negative impacts to its habitat in woody draws. Livestock grazing and noxious weeds are reported to threaten populations. Information on scope and severity of these threats is needed (MTNHP Threat Assessment 2021).