Holy basil grows up to 0.5-1 m high, depending on growing conditions.
Tulsi is a perennial in tropics but is best treated as a half-hardy annual here as northern European light levels are insufficent during winter for it to keep growing. It has long purple flowers and smooth green foliage with a spicy fragrance.
Harvest young shoots in early morning for maximum flavour and scent.
Half-hardy annual, usually best under cover on a sunny windowsill or a greenhouse, even during the summer, but can be grown in a sheltered place outdoors in mild areas. Minimum temperature 18ºC.
Sow in moderate heat, 18-20ºC/65-70ºF, during April-May
using any good seed compost with added 1/3 extra sharp grit for best results.
Cover seed very thinly with sieved compost or vermiculite.
If plants are very well established and growing in a greenhouse, you may be able to save seed to keep for next year, which may be easier to germinate than bought seed. Otherwise, remove spent flowers to prolong the life of plant.
As seedlings are large enough to handle, pot up until they are in a 30cm pot. If trying outside, plant out in summer in a sunny open place, perhaps near a south-facing wall. Feed potted plants fortnightly with a general liquid fertiliser and keep well watered, allowing plants to dry between waterings.
Basil Wilt occasionally causes plants to suddenly collapse and turn brown overnight. Don't try to save them but put them in the dustbin and wash your hands as well as the pots thoroughly before touching any other plants.This disease can be transmitted by infected seed, compost or sap regurgitated from another infected plant by aphids, so wash off any greenfly you see on the plants by holding it sideways under a running tap or squish them between fingers.
Seeds and young plants can be obtained from a number of supplier.