|Photo by the Atlas of Florida Plants Database|
|Division:||Magnoliophyta - Flowering plants|
|Class:||Liliopsida - Moncots|
| Aristida purpurascens|
|Natural range of Aristida purpurascens from USDA NRCS Plants Database.|
Varieties: A. purpurascens var. purpurascens; A. purpurascens var. tenuispica; A. purpurascens var. virgata, A. purpurascens var. minor Vasey
A. purpurascens is a monoecious perennial graminoid that tolerates moderate shade. In sandhill pine communities, it can be found in a green or strongly glaucous-blue form. It reaches heights of 1.5-2.0 ft (0.46-0.61 m) with flat narrow leaf blades 4-12 in (10.2-30.5 m) long. Seedheads have a narrow panicle that is 1/3 to 1/2 the height of the plant. Awnes are 1/2 to 3/4 inches long and twice as thick at the base. Seeds contain barblike hairs at the base.
This species is found in dry habitats including pine savannas, fields, and waste places, especially those containing sandy or rocky soils. A study in Michigan old fields showed A. purpurascens had the second highest standing crop, which peaked in August at 270 g m-2 dry weight. In Maryland pine-cedar savannas, A. purpurascens was the second most important species (IV = 23.5%; Importance Value Index[IV] - calculated by summing the relative frequency and relative cover). Lesser importance was found in Maryland serpentine barrens between 1989 and 1992 (IV = 1.4-6.5%). Despite its importance in dryer systems, A. purpurascens is also observed in seepage bogs with similar, or slightly greater, coverage as pine savannas. In Louisiana sandstone outcrops where A. purpurascens also occurs, topsoil calcium were measured at 2267.5 ppm and magnesium at 586.5 ppm. Dead material of A. purpurascens disappears from 2.0-2.7 mg g-1 in the fall (mid July-mid November) and 0.1-1.0 mg g-1 the rest of the year in a Michigan old field.
Seeds production usually peaks in June.
This species is thought to be dispersed by gravity. 
A. purpurascens withstands annual burning. On Eglin Air Force Base, Florida, May and July burns increased the percentage of flowering culms on A. purpurascens. In Maryland serpentine barrens, clearing and the combination of clearing and burning increased the importance value percentage to between 3.0-12.2% from between 1.4-6.5%
Use by animals
Seeds from this grass compose 2-5% of the diet of some terrestrial birds. A study in Michigan showed the seeds of A. purpurascens was also abundant in the caches of prairie deer mice (Peromyscus maniculatus bairdii). For a few weeks in the spring cattle can graze arrowfeather, but in the rest of the year it is considered a low quality forage.
Conservation and Management
To reduce the abundance of A. purpurascens, grazing can be allowed for 2-3 weeks in the spring just before seedheads appear.
Cultivation and restoration
References and notes
- Weakley A. S.(2015). Flora of the Southern and Mid-Atlantic States. Chapel Hill, NC: University of North Carolina Herbarium.
- USDA, NRCS. (2016). The PLANTS Database (http://plants.usda.gov, 14 December 2017). National Plant Data Team, Greensboro, NC 27401-4901 USA.
- Magee P. (2012). Plant fact sheet: Arrowfeather threeawn Aristida purpurascens. United States Department of Agriculture, Natural Resources Conservation Service, Baton Rouge, LA.
- Allred K. W. (1986). Studies in the Aristida (Gramineae) of the southeastern United States. IV. Key and Conspectus. Rhodora 88(855):367-387.
- Catling P. M., Reznicek A. A., Riley J. L. (1977). Some new and interesting grass records from southern Ontario. Canadian Field-Naturalist 91(4):350-359.
- Drewa P. B., Platt W. J., and Moser B. (2002). Community structure along elevation gradients in headwater regions of longleaf pine savannas. Plant Ecology 160:61-78.
- Wiegert R. G. and Evans F. C. (1964). Primary production and the disappearance of dead vegetation on an old field in southeastern Michigan. Ecology 45(1):49-63.
- Tyndall R. W. and Farr P. M. (1989). Vegetation structure and flora of a serpentine pin-cedar savanna in Maryland. Castanea 54(3):191-199.
- Tyndall R. W. (1994). Conifer clearing and prescribed burning effects to herbaceous layer vegetation on a Maryland serpentine "barren." Castanea 59(3):255-273.
- Kley J. E. V. (1999). The vegetation of the Kisatchie Sandstone Hills, Louisiana. Castanea 64(1):64-80.
- Kirkman, L. Katherine. Unpublished database of seed dispersal mode of plants found in Coastal Plain longleaf pine-grasslands of the Jones Ecological Research Center, Georgia.
- Shepherd B. J., Miller D. L., and Thetford M. (2012). Fire season effects on flowering characteristics and germination of longleaf pine (Pinus palustris) savanna grasses. Restoration Ecology 20(2):268-276.
- Howard W. E. and Evans F. C. (1961). Seeds stored by prairie deer mice. Journal of Mammalogy 42(2):260-263.