Henna is a tropical shrub or small tree which requires a heated greenhouse to grow all year round in the British Isles. The deliciously scented white flowers are carried in large clusters at the ends of the branches once a year, usually after the monsoon in North India, but in the UK in late summer. Henna is sometimes grown as an ornamental plant in Asian gardens.
Cannot survive outdoors even in the hottest summers here. Minimum temperature 22ºC.
From seed or semi-hardwood cuttings and offsets.
Henna in India needs a high rainfall as well as a fairly good soil.
In the British Isles, sow seeds in March-April, at 25ºC/75ºF, cover lightly with compost and be patient: germination can be slow, sometimes several months. The process may be speeded by sealing the pot inside a plastic bag and putting it in a warm place, such as an airing cupboard. Once germinated, pot seedlings up on into individual pots and keep in a sunny position. Water well during the growing season and repot annually every spring until the plant is in a 45cm pot.
Flowering will not take place until the plants are at least 5 or 6 years old, and usually needs high winter temperatures to stimulate the plants to start, although once a pattern of flowering is begun, it usually repeats reliably in following years. Surplus leaves can be clipped form the plant as soon as it is large enough, and these can be used to make your own dye for cloth or hair.