The Digitaria genus, commonly known as crabgrass, is widely recognized as a persistent weed in lawns and agricultural fields. This perception often overshadows the plant’s significant ecological and economic value. While species like large crabgrass (Digitaria sanguinalis) and smooth crabgrass (Digitaria ischaemum) are viewed as agricultural nuisances, the genus encompasses nearly 300 species with diverse beneficial applications. Examining the broader genus reveals a history of use as a resilient food source and a source of compounds with therapeutic potential. The plant’s ability to thrive in poor or disturbed soils also grants it an important function in environmental management, moving the conversation beyond mere weed control to appreciate its utility.
A Sustainable Forage and Grain Source
Certain Digitaria species offer a highly palatable and nutritious forage option for livestock, particularly during the hot summer months when cool-season grasses often falter. This warm-season annual grass is noted for its high yield and quality, often outperforming other warm-season grasses like bahiagrass and bermudagrass. Its forage can achieve crude protein levels ranging from 11% to 15.5%, with some reports indicating up to 21% under optimal conditions.
The total digestible nutrients (TDN) in crabgrass forage typically measure between 58% and 63%, making it a highly digestible feed that supports the energy needs of grazing animals. Improved varieties of crabgrass, such as ‘Red River,’ can produce up to five tons of dry matter per acre. Its ability to reseed itself annually, behaving almost like a perennial, makes it a reliable and sustainable component for extending the grazing season into the late summer and fall.
The seeds of several Digitaria species have a long history as a human grain. Species like white fonio (D. exilis) and black fonio (D. iburua) are staple crops in West Africa, valued for their resilience in challenging climates and their nutritional content. Historically, D. sanguinalis was cultivated by Slavic peoples in Eastern Europe, earning it the name “Polish millet,” where the grain was used in porridges and soups.
The seeds can be toasted and ground into a fine white flour, which has been used as a substitute for semolina. Their ability to thrive in arid or low-fertility conditions is driving renewed interest in the context of global food security.
Bioactive Compounds and Traditional Uses
The Digitaria genus has been utilized across different cultures for its therapeutic properties. Traditional medical systems have employed various species as a local antibiotic and for the treatment of inflammatory diseases and skin ailments. In parts of Africa, Digitaria horizontalis has been used in traditional medicine to address neurological disorders, with studies supporting its neuropharmacological activities.
Traditional applications include using a decoction of the plant as a remedy for conditions such as cataracts and to treat gastrointestinal disorders. Modern scientific inquiry has begun to isolate and characterize the specific phytochemicals responsible for these effects. For instance, the leaves of D. sanguinalis contain compounds such as veratric acid, maltol, and (-)-loliolide.
Veratric acid has demonstrated anti-inflammatory and anti-fungal properties in laboratory settings. The compound (-)-loliolide has been identified as possessing antimicrobial activity. Furthermore, methanol extracts from the leaves of D. sanguinalis have shown moderate anti-MRSA activity, indicating potential against antibiotic-resistant bacteria.
Role in Soil Health and Erosion Control
The ecological function of crabgrass includes stabilizing and improving soil health. The plant species within the Digitaria genus rapidly colonize disturbed environments due to their dense, fibrous root system and prostrate, mat-like growth habit. This aggressive growth pattern makes crabgrass highly effective for preventing soil loss caused by wind and water erosion. The extensive root network binds the soil particles together, which is particularly beneficial in areas prone to erosion or on sandy soils.
Crabgrass is successfully used as a temporary cover crop, especially in agricultural systems that experience a summer slump in perennial grass production. When used as a cover crop, it adds organic matter back into the ground and can improve soil structure during fallow periods. Certain species, such as Digitaria eriantha, are largely resistant to root-knot nematodes, making them a recommended rotation crop on sandy soils infested with this common pest.