Tacca chantrieri aka Black Bat Flower

Tacca chantrieri, or bat flower, stays green all year. This perennial lives for more than two years. It belongs to the yam family, Dioscoreaceae. Its home range runs from Assam to southern China and Peninsular Malaysia. It grows in damp woods, valleys, and near rivers. Thick stems called rhizomes creep sideways below the soil. Long leaf stalks grow from them in upright clumps.

Garden plants grow about 1.6–3.3 feet (0.5–1 metre) tall and wide. They reach full size in two to five years. The leaves are oblong or shaped like a lance. They have dark green tops and paler undersides. RHS gives leaf lengths of 0.6–1.8 feet (0.17–0.55 metres). Useful Tropical Plants reports leaves reaching 2 feet (0.6 metres). Bare flower stalks grow to about 2.1 feet (0.65 metres).

Broad bracts, which are changed leaves, ring each flower cluster. These clusters grow at the tips of the stalks. The bracts can be green, brown, or almost black. Each flower has five green petals. Thin strands trail for about 0.8 feet (0.25 metres). They range from dark green to maroon and black. The dark bracts and strands make blooms look like bats. RHS lists blooms in summer. Chicago Botanic Garden lists blooms from January through April.

This plant from the tropics needs warmth, shade, and steady moisture. In cool regions, RHS says to use a greenhouse. Keep it above 13°C. Give it bright light, but screen out direct sun. In warm regions, grow it outside in part shade. Choose a spot that shields it from harsh weather. Use rich, acidic loam that stays moist but drains well. For pots, RHS suggests equal parts leaf mould and coarse bark. Give plenty of water all year and mist the leaves. Add slow-release feed. In summer, also feed the leaves monthly at half strength. Repot every two or three years, and remove rotting rhizomes. RHS rates it H1B; Chicago lists USDA zones 10–13.

Bat flower suits pots and patios where warmth allows. It needs no pruning. In spring, grow more from seed or split plants. You can also use rhizome pieces that bear buds. Red spider mites and tarsonemid mites may attack greenhouse plants. Grey mould can cause trouble too. Useful Tropical Plants records tender leaves and flower clusters in curries. It also records rhizome extracts used on skin for rheumatism. Vietnamese herbal practice forbids taking the rhizome by mouth. The rhizomes supply diosgenin to make steroid drugs. These records do not prove safety for pets or all plant parts.