Digitaria ciliaris aka Tropical Finger Grass

Digitaria ciliaris is a grass also called southern crabgrass. Its family is Poaceae, the grass family. Kew places its native range in east and southeast China. It reaches Vietnam, too. It also spans southern Kyushu in Japan to Taiwan. The grass now grows in many tropical and subtropical regions. US records range from Pennsylvania to Florida and California. It grows in lawns, pastures, and crop fields. It also grows on ground that people have disturbed.

This warm-season grass forms clumps or creeps across the soil. NCSU and Useful Tropical Plants call it an annual. Kew lists it as a perennial instead. Reported heights range from about 0.7–3.3 feet [0.2–1 metre]. Useful Tropical Plants also gives a height of 2.3 feet [0.7 metres]. The stems may stand up or spread along the ground. They are green and range from round to flat. New roots can grow at nodes, the joints along stems. These roots help patches take hold.

Green leaves grow in turn along the stems, with smooth edges. The blades are narrow, but some widen toward an oval shape. Leaves range from about 0.25–0.5 feet [0.08–0.15 metres] long. Fine ribs mark the sheaths that wrap around the stems. Hairs grow near the sheath bases. Long stems hold small flowers above the leaves. Straight flower clusters, called racemes, reach about 0.7 feet [0.2 metres] long. NCSU lists green or brown flowers in spring and summer. Wind carries the pollen. Small, pale brown seeds form in summer and fall.

The grass grows in full sun and tolerates partial shade. It favors moist soil and grows well in rich ground. Useful Tropical Plants says it favors sand or loam. NCSU also lists clay as a soil it can grow in. PFAF gives USDA zones 7–10. NCSU notes that frost kills it. Plants grow fast and spread by seed. Thick mats can be hard to remove. Pulling young plants by hand avoids the extra roots of older growth. Mulch can cut seed sprouting in garden beds.

Unwanted spread is its main garden problem, not care for its looks. Useful Tropical Plants calls it invasive in many areas. Cover already in place can help keep soil from washing away. It can also supply mulch or compost. NCSU reports that livestock eat this species as forage. Evidence for its use as human food is still weak. PFAF lists an edible part but does not name it. It also says the seeds may be edible. Useful Tropical Plants reports no known use as food. Both sources report no known hazards or uses as medicine. These reports do not show that it is safe to eat.