Panic Grass - Dichanthelium acuminatum
Panicum acuminatum, Dichanthelium lanuginosum, Panicum lanuginosum, Panicum occidentale
State Rank Reason (see State Rank above)
Dichanthelium acuminatum is common and ubiquitous in most of the U.S. and Canada (Freckmann and Lelong in FNA 2007). The species is polymorphic and 10 major subspecies have been described, but many overlap in characteristics and widespread introgression from other Dichanthium species contributes to taxonomic difficulties (Freckmann and Lelong in FNA 2007). However, only subspecies sericeum has been documented in Montana. Dichanthelium acuminatum susp. sericeum colonizes wet soils around the edges of hot springs. It occurs widely scattered through south-central, southwest, and northwest Montana, where it can be locally common. Observation data is aging, and some re-visits to known populations did not re-locate the grass. Given its narrow habitat requirements, potential threats from ground disturbance and recreation, and lack of current data a Species of Concern rank is warranted. Current data on locations, population sizes, threats, and how it responds to natural and manmade disturbances are greatly needed.
- Details on Status Ranking and Review
ScoreF - 20,000-200,000 sq km (~8,000-80,000 sq mi)
Comment87,421 square kilometers
Area of Occupancy
ScoreD - 6-25 4-km2 grid cells
CommentPlant occurs in 16 of the 30,590 4x4 square-kilometer grid cells that cover Montana.
Number of Populations
ScoreB - 6 - 20
Comment17 observations representing 16 distinct occurrences. Adjacent occurrences in YNP-WY are also present.
ScoreA - Very narrow. Specialist or community with key requirements scarce
CommentWet soil around hot springs, which represent limited and/or fragile habitat.
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 with a ligule of long (2-6mm) hairs. Fall shoots arising from all but the upper nodes.
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).
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
, 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.
in wet soils around hot springs.Wilcox’s Panic Grass
– Dichanthelium wilcoxianum
* 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
, 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
) is a rhizomatous, perennial grass while Montana's other Panicum
species are annuals.
Throughout most of North America; subspecies sericeum is more narrowly confined to the U.S. in the Rocky Mountain states, UT, CO, WY, ID and MT (Lesica et al. 2012).
Observations in Montana Natural Heritage Program Database
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
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.
Threats or Limiting Factors
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).
- Literature Cited AboveLegend: View Online Publication
- Flora of North America Editorial Committee. 2003. Flora of North America North of Mexico. Vol. 25. Magnoliophyta: Commelinidae (in part): Poaceae, part 2. Oxford Univ. Press, New York. xxv + 781 pp.
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
- McGregor, R.L. (coordinator), T.M. Barkley, R.E. Brooks, and E.K. Schofield (eds). 1986. Flora of the Great Plains: Great Plains Flora Association. Lawrence, KS: Univ. Press Kansas. 1392 pp.