Perennial, densely tufted top grass. Forms bushy tussocks in pastureland. Shoots emerge early in the spring. Culms are 50–100 cm tall. Flowers June to August. Tufted hair grass growth mainly on damp or marshy grassland, ditches, riverbanks and damp woodland. Rarely found on dry sites. Not tolerant of flooded and waterlogged soils. Tufted hair grass is regarded as the most troublesome weed on permanent grassland. Livestock tend to avoid it on account of its tough, spiky leaves, which allows it to spread undisturbed. Seed dispersal can be prevented by constant short mowing. The feed value of 3 is correspondingly low. Horses are more likely than cattle to graze the young tussocks.
Botanical features
| Leaf | Leaf folded in the bud, leaf sheath open and glabrous. Leaf blade open, usually 7 very distinct, rough ribs and sharp edges. Leaves glabrous, dark green, lighter shade of green showing between the ribs. Ligule long and rough, pointed tip, split and white. Auricles absent. |
| Culm | The dense tussocks of closely packed shoots produce 50–100 cm long culms. |
| Inflorescence | Panicle, sometimes pendulous, up to 20 cm in length. Five or more side branches on the lower node of the panicle. Numerous relatively small spikelets 3–5 mm long, most with 2 florets. Lemmas shorter than glumes, awn emerging from the base which barely extends beyond the spikelets. |
| Fruit | Grain with soft, silvery grey husk. Lemma truncated at the top and toothed with fine-toothed awn arising from the base. This may be straight, curved or bent. Pedicel long with whitish hairs. The brown caryopsis is visible. TSW 0.2–0.3 g. |