Large Crabgrass (also known as hairy crabgrass, purple crabgrass, or finger grass)
Kingdom: Plantae, Division: Tracheophyta, Class: Liliopsida, Order: Poales, Family: Poaceae, Genus: Digitaria, Species: D. sanguinalis · Poaceae (True Grass family) · Specialized (grass blade with a membranous ligule), deciduous annual
Species
Digitaria sanguinalis
Leaf Type
Specialized (grass blade with a membranous ligule), deciduous annual
Family
Poaceae (True Grass family)
Shape
Linear, with a flat, narrow blade tapering to a point
Size
Blades typically measure 3 to 6 inches long and 1/4 to 1/2 inch wide, which is standard for mature foliage of this species
Margin
Entire (smooth) but may feel slightly rough or scabrous
Arrangement
Alternate along the branching, decumbent stems
Rarity
Very Common
Color & Pattern
Light green to grayish-green, sometimes developing a purplish or reddish tinge along the stems and leaf sheaths as it matures or faces stress; upper and lower surfaces are similar with prominent sparse hairs
Venation Pattern
Parallel venation with a distinct central midrib running the length of the blade
Texture & Surface
Slightly rough with soft hairs, particularly near the base of the leaf blade and along the sheath; dull matte finish
Description
Large crabgrass is a sprawling annual grass that germinates in spring and grows aggressively through the summer. It features branching stems that root at the lower nodes, forming wide mats. The inflorescence, shown in the image, consists of a terminal cluster of slender, finger-like spikes (racemes) that produce numerous tiny seeds before dying off with the first autumn frosts
Key Features
Finger-like spike inflorescences branching from a single point, hairy leaf sheaths, and a sprawling, mat-forming growth habit with the ability to root at lower nodes
Habitat
Thrives in disturbed soils, lawns, agricultural fields, gardens, and along pathways; prefers high sunlight and well-draining soils but tolerates compaction and drought
Geographic Range
Native to Europe and temperate Asia, but now naturalized globally across temperate and subtropical regions worldwide, often considered a widespread weed
Condition Notes
The pictured inflorescence and upper stems appear healthy and at peak maturity for seed production; Good condition grade
Interesting Facts
The genus name 'Digitaria' comes from the Latin word 'digitus', meaning finger, referencing the finger-like arrangement of the seed spikes. Despite being a notorious lawn weed, its seeds are an important food source for ground-feeding birds and small mammals
Medicinal & Uses
Generally regarded as a weed rather than a useful herb; historically, some cultures have harvested the seeds for grain during food shortages, though the effort required is high
Ecological Role
Acts as a pioneer species in disturbed ground, helping to cover bare soil and prevent erosion, though it can outcompete native groundcovers and desirable turfgrasses
Similar Species
Smooth crabgrass (Digitaria ischaemum) is very similar but lacks hairs on the leaf blades and sheaths, and goosegrass (Eleusine indica) has thicker, more flattened stems and a silvery-white center at the base
Foraging Tips
Look in heavily trafficked lawns, sidewalk cracks, and garden beds during mid-to-late summer when the distinctive finger-like seed heads emerge and rise above the turf
Toxicity Warning
Non-toxic; safe for humans and animals, though large amounts of mature grass may cause minor digestive upset in pets