Digitaria

Digitaria
Digitaria sanguinalis
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Monocots
(unranked):	Commelinids
Order:	Poales
Family:	Poaceae
Subfamily:	Panicoideae
Tribe:	Paniceae
Genus:	Digitaria Haller[1]
Species
See text.

Digitaria is a genus of about 300 species of grass (family Poaceae) native to tropical and warm temperate regions. Common names include crabgrass, finger-grass, and fonio. They are slender monocotyledonous annual and perennial lawn, pasture, and forage plants; some are often considered lawn pests. Digitus is the Latin word for "finger", and they are distinguished by the long, finger-like inflorescences they produce.

All crabgrasses have similar growth habits and flowering structures, but species are separated by minor differences in the flower structures and leaf pubescence.^[2] They typically have spreading stems with wide flat leaf blades that lie on the ground with the tips ascending. The inflorescence is a panicle in which the spike-like branches are arranged in digitate fashion. The spikelets are arranged in two rows on an angled or winged rachis. Each spikelet has two florets, only one of which is fertile. The first bracts at the base of the spikelets are either very minute or absent.^[3]

Crabgrass seed has a long germination period; if conditions are right, it can germinate throughout the growing season. Crabgrasses occur in tropical, subtropical, and temperate regions of both hemispheres.

Crabgrasses have uses despite being classified by many as weeds. The seeds, most notably those of fonio, can be toasted and ground into a flour, which can be used to make porridge or fermented to make beer. Fonio has been widely used as a staple crop in parts of Africa. It also has decent nutrient qualities as a forage for cattle.

Lawns

The most prevalent species of Digitaria in North America are Large Crabgrass (D. sanguinalis), sometimes known as Hairy Crabgrass; and Smooth Crabgrass (D. ischaemum). These species often become problem weeds in lawns and gardens, growing especially well in lawns that are watered lightly, underfertilized, poorly drained, and growing thinly. They are annual plants, and one plant is capable of producing 150,000 seeds per season. The seeds germinate in the late spring and early summer and outcompete the domesticated lawn grasses and expand outward in a circle up to 12 inches in diameter. In the fall when the plants die they leave large voids in the lawn. The voids then become prime areas for the crabgrass seeds to germinate the following season.

Biological control is preferable over toxin use on lawns as crabgrass emergence is not the cause of poor lawn health but a symptom, and crabgrass will return annually if the lawn health is not improved by fertilization and proper watering. Crabgrass is quickly outcompeted by healthy lawn permanently because as an annual plant, crabgrass dies off in fall and needs open soil without other vegetation for the germination of its seeds the next spring to survive.

Selected species

Digitaria ammophila – Silky Umbrella Grass Digitaria bicornis (Lam.) Roemer & J.A.Schultes ex Loud. – Asian Crabgrass Digitaria brownii (Roem. & Schult.) Hughes – Cotton Panic Grass Digitaria californica (Benth.) Henrard – Arizona Cottontop Digitaria ciliaris (Retz.) Koeler – Summer Grass, Southern Crabgrass Digitaria ctenantha (F.Muell.) Hughes – Comb Finger Grass Digitaria didactyla Willd. – Queensland Blue Couch Digitaria eriantha Steud. – Pangolagrass, Smut's Finger Grass Digitaria exilis (Kippist) Stapf – Fonio Digitaria filiformis (L.) Koeler – Slender Crabgrass Digitaria gracillima – Longleaf Crabgrass Digitaria horizontalis Willd. – Jamaican Crabgrass Digitaria insularis (L.) Fedde – Sourgrass Digitaria ischaemum (Schreb.) Schreb. ex Muhl. – Smooth or Small Crabgrass, Smooth Finger-grass

Digitaria longiflora (Retz.) Pers. – Indian Crabgrass Digitaria milanjiana (Rendle) Stapf – Madagascar Crabgrass Digitaria nuda Schumacher – Naked Crabgrass Digitaria pauciflora Hitchc. – Twospike Crabgrass Digitaria radicosa (C.Presl) Miq. – Trailing Crabgrass Digitaria sanguinalis (L.) Scop. – Hairy Crabgrass, Large Crabgrass Digitaria setigera Roth ex Roemer & J.A.Schultes – East Indian Crabgrass Digitaria serotina (Walt.) Michx. – Dwarf Crabgrass Digitaria texana A.S.Hitchc. – Texas Crabgrass Digitaria velutina (Forssk.) P.Beauv – Velvet Crabgrass Digitaria villosa (Walt.) Pers. – Shaggy Crabgrass Digitaria violascens Link – Violet Crabgrass[4][5]

Images

Crabgrass

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References

1. ^ "Genus: Digitaria Haller". Germplasm Resources Information Network. United States Department of Agriculture. 2007-10-05. http://www.ars-grin.gov/cgi-bin/npgs/html/genus.pl?3700. Retrieved 2010-11-06. 
2. ^ Andrea S. Vega and Zulma Rúgolo de Agrasar, Morphological interpretation of the spikelet in Digitaria atra (Poaceae: Panicoideae: Paniceae) and emended generic description American Journal of Botany (2001)
3. ^ Museum of Natural History, University of Minnesota by A.F. Cholewa and J.F. Bell
4. ^ "Digitaria". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=203845. Retrieved 2010-11-06. 
5. ^ "GRIN Species Records of Digitaria". Germplasm Resources Information Network. United States Department of Agriculture. http://www.ars-grin.gov/cgi-bin/npgs/html/splist.pl?3700. Retrieved 2010-11-06. 

• Gilani, S.S.; Khan, M.A.; Shinwari, Z.K.; Nasim, A.A. (2003) Taxonomic relationsip of Digitaria in Pakistan Pakistan Journal of Botany, 35(3): 279–282.
• Gilani, S.S.; Khan, M.A.; Shinwari, Z.K.; Hussain, F.; Yousaf, Z. (2003) New subspecies of Digitaria sanguinalis from Pakistan Pakistan Journal of Botany, 35(3): 261–278.