Jamaican crabgrass

Digitaria horizontalis, commonly called Jamaican crabgrass or sourgrass, is an annual or short-lived perennial grass in the family Poaceae, native to the tropical Americas and now widely naturalised throughout the warmer regions of the world as a weed of crops, pastures and disturbed ground. Plants form spreading mats, with prostrate or decumbent culms that root readily at the lower nodes, the flowering stems then ascending to 30 to 80 centimetres. Leaf blades are flat, linear-lanceolate, soft, light green, with finely scabrid margins and a membranous ligule. The inflorescence is digitate, consisting of three to many slender spike-like racemes spreading horizontally from the top of the culm (hence horizontalis). Spikelets are small, narrowly lanceolate, paired, with one nearly sessile and one short-pediceled, each bearing two florets. The species reproduces rapidly by seed and stolons.