|Photo taken by Kevin Robertson|
|Division:||Magnoliophyta - Flowering plants|
|Class:||Liliopsida – Monocotyledons|
|Family:||Poaceae ⁄ Gramineae|
| Digitaria filiformis|
|Natural range of Digitaria filiformis from USDA NRCS Plants Database.|
Common name: Slender crabgrass
Synonyms: Syntherisma filiformis (L.) Nash; Panicum filiforme L.
There are three varieties. D. filiformis var. laeviglumis, D. filiformis var. filiformis; and D. filiformis var. dolichophylla. The variety laeviglumis is rare and endemic to New Hampshire in peaty depressions on granite ledges.
Generally, for the Digitaria genus, they are "annuals; internodes glabrous. Leaves cauline; blade margins cartilaginous, scaberulous; sheath margins usually scarious; ligules membranous. Racemes racemose, ascending; rachis usually winged, scaberulous. Spikelets plano-convex, ellipsoid, acute. First glume usually absent, 2nd glume villous on nerves and margins, acute, sterile lemma 5-7 nerved, acute; fertile lemma and palea nerveless, cartilaginous, glabrous, acute; fertile lemma margins flat, hyaline. Grain whitish to brownish, ellipsoid. These plants are out worst field and gardens weeds."  Specifically, for D. filiformis species, they are "cespitose annual; culms 3-12 dm tall, nodes glabrous. Blades to 15 cm long, 2-4 mm wide, papillose-hirsute and scaberulous above, glabrous or occasionally pilose to hirsute beneath; sheaths papillose-hirsute; ligules erose to lacerate, 0.5-1 mm long. Racemes 2-7, ascending, 3-12 cm long; rachis trigonous, wingless, scaberulous. Spikelets 1.8-2.5 mm long; pedicels scaberulous, -.5-3 mm long. Second glume 5- nerved, 1.2-1.5 mm long, sterile lemma margins ciliate, 1.8-2 mm long; fertile lemma and palea purple, papillose lined, 1.8-2 mm long. Grain 1-1.2 mm long, whitish to brownish, ellipsoid." 
In the Coastal Plain region, Digitaria filiformis is found in pine-oak, oak-palmetto and open longleaf pine-wiregrass woodlands along with turkey-oak sand ridges, banks of ditches in saltmarshes, and transition zones between longleaf pine, turkey oak sand ridge and pine flatwoods. Occasionally has been found in mesic flatwoods in Hillsborough County, Florida.  It has been vouchered in an outcrop habitat on Panola Mountain located within Henry-Rockdale county line, southeast of Atlanta, Georgia.  D.filiformis also occurs in the Kansas-Nebraska Drift Loess Hills characterized by divides with moderately steep slopes and silt loams and silty clay loam soils occasionally broken by bedrock outcrops. 
D. filiformis var. laeviglumis is a globally rare crabgrass endemic to to Rock Rimmon in urban Manchester, New Hampshire. This areas is characterized by an unusual temperate ridge-cliff-talus system.
Disturbed habitats in the Coastal Plain region that have documented populations of D. filiformis include fallow and open weedy park fields, roadsides, powerline corridors, clobbered longleaf pine forest and cleared sand pine and pine flatwood communities.
In the Coastal Plain region it has been documented as occurring on “upland, sandhill areas on droughty, infertile entisols and ultisols with loamy sand to sandy loam surface horizons.”  It has also been recorded to occur in silty soils. Light levels have observed to be partially shaded.
Species found associated with D. filiformis in the Coastal Plain region are Liatris, Pityopsis, Aristida stricta, Aristida purpurascens, Andropogon gerardii, Pteridium aquilinum, Nolina atopocarpa, Hedeoma graveolens, Hedyotis procumbens, Angelica dentata, Rhynchospora globularis, Solidago and Eragrostis.
Flowering and fruiting have been observed in June, August, September, October and November.
This species is thought to be dispersed by gravity. 
This species has been found in habitat types that are maintained by fire, which implies some level of fire tolerance.
Use by animals
In the Kansas-Nebraska Drift Loess Hills, white-tailed deer were found to graze D. filiformis year-round.
Conservation and management
Cultivation and restoration
References and notes
- []GoBotany. Accessed: April 29, 2016
- Radford, Albert E., Harry E. Ahles, and C. Ritchie Bell. Manual of the Vascular Flora of the Carolinas. 1964, 1968. The University of North Carolina Press. 138. Print.
- Florida State University Robert K. Godfrey Herbarium database. URL: http://herbarium.bio.fsu.edu. Last accessed: June 2014. Collectors: Loran C. Anderson, H. E. Ahles, Tom Barnes, Michael B. Brooks, Robert W. Simons, Dianna Hall, R. Kral, R. K. Godfrey, Sidney McDaniel, R. A. Norris, H. R. Reed, Cecil R. Slaughter, Frankie Snow, A. E. Redford, C. Simon, A. A. Eaton, Robert L. Lazor, Bruce Hansen, JoAnn Hansen, W. A. Silveus, A. F. Clewell, Robert Blaisdell, O. Lakela, George R. Cooley, Richard J. Eaton, Daniel B. Ward, Paul O. Schallert, and A. H. Curtiss. States and Counties: Florida: Bay, Brevard, Clay, Dixie, Duval, Escambia, Franklin, Flagler, Gadsden, Hillsborough, Jackson, Jefferson, Leon, Levy, Liberty, Madison, Nassau, Osceola, Putnam, Sarasota, St. Johns, Taylor, Wakulla, and Washington. Georgia: Camden, Coffee, and Grady. Mississippi: Pearl River and Oktibbeha. North Carolina: Alexander. South Carolina: Hampton. Virginia: Pulaski. Other Countries: Switzerland.
- Myers, J. H., and Richard P. Wunderlin (2003). "Vascular Flora of Little Manatee River State Park, Hillsborough County, Florida." Castanea 68(1): 56-74.
- Bostick, P. E. (1971). "Vascular Plants of Panola Mountian, Georgia " Castanea 46(3): 194-209.
- Watt, P. G., G.L. Miller, and R.J. Robel (1967). "Food Habits of White-tailed Deer in Northeastern Kansas." Transactions of the Kansas Academy of Science 70(2): 223-240.
- Nichols, W. F. and J. Hoy (2014). "A TEMPERATE RIDGE-CLIFF-TALUS SYSTEM IN AN URBAN SETTING: ROCK RIMMON IN MANCHESTER, NEW HAMPSHIRE." Rhodora 116(965): 83-98.
- Archer, J. K., D. L. Miller, et al. (2007). "Changes in understory vegetation and soil characteristics following silvicultural activities in a southeastern mixed pine forest." Journal of the Torrey Botanical Society 134: 489-504.
- 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.