Poa sandvicensis is a perennial grass in the Poaceae (grass) family with densely tufted, mostly erect culms (stems) 0.3 to 1 m (1 to 3.3 ft) tall. The short rhizomes (underground stems) form a hardened base for the solid, slightly flattened culms. The leaf sheaths are closed and fused but may split with age. The toothed ligule (appendage where leaf sheath and blade meet) completely surrounds the culm and has a hard tooth extending upward from the mouth of the sheath. The leaf blades are 10 to 20 cm (4 to 8 in) long and up to 6 mm (0.2 in) wide. The flowers occur in complex clusters with lower panicle (primary) branches up to 10 cm (4 in) long. The lemmas (inner bracts) have only a sparse basal tuft of cobwebby hairs. The fruits are golden brown to reddish brown, oval grains.