Crabgrass
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Digitaria is a genus of about 300 species of grass (family Poaceae) most commonly known as crabgrasses. They are slender monocotyledonous annual and perennial lawn, pasture, and forage plants that are often considered lawn pests. Digitus is the Latin word for "finger", and crabgrasses 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. They typically have spreading stems with wide flat leaf blades that lay 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. (Cholewa and Bell)
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.
The most commonly known species of Digitaria are Large crabgrass (D. sanguinalis) and Smooth crabgrass (D. ischaemum), which are often considered problem weeds. First, they are annual plants, and one plant is capable of producing 150,000 seeds per season. The plants invade lawns during the spring and summer and then leave large voids in the fall and winter when they die off. Second, crabgrass has an ungainly texture that often interrupts the uniformity of a lawn. In vegetable gardens, crabgrass can quickly out-compete desirable plants, causing considerable yield reductions.
Still, despite their weediness, crabgrasses do have a few redeeming qualities. The seeds can be toasted and ground into a flour, which can be used to make porridge or even fermented to make beer. It also has decent nutrient qualities as a forage for cattle.
Partial species list
- Digitaria ammophila Silky Umbrella Grass
- Digitaria bicornis Finger Grass
- Digitaria brownii Cotton Panic Grass
- Digitaria californica Arizona Cottontop
- Digitaria ciliaris Summer grass, Southern crabgrass
- Digitaria ctenantha Comb Finger Grass
- Digitaria didactyla Queensland Blue Couch
- Digitaria eriantha Pangolagrass
- Digitaria filiformis Slender crabgrass
- Digitaria gracillima Longleaf crabgrass
- Digitaria horizontalis Jamaican crabgrass
- Digitaria ischaemum Smooth or Small crabgrass
- Digitaria longiflora Indian crabgrass
- Digitaria milanjiana Madagascar crabgrass
- Digitaria nuda Naked crabgrass
- Digitaria pauciflora Twospike crabgrass
- Digitaria radicosa Trailing crabgrass
- Digitaria sanguinalis Hairy crabgrass, Northern crabgrass, Pigeon grass, Large crabgrass
- Digitaria serotina dwarf crabgrass
- Digitaria texana Texas crabgrass
- Digitaria velutina Velvet crabgrass
- Digitaria villosa Shaggy crabgrass
- Digitaria violascens Violet crabgrass
References
- Museum of Natural History, University of Minnesota by A.F. Cholewa and J.F. Bell
- 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)