Germination temperature
Best at about 35 °C (95 °F): over 90% germination, against 71-74% at 20-30 °C (68-86 °F).
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Henna is a heat-loving shrub or small tree grown for its dye leaves and as a hedge in dry, hot regions. The tiny seed needs warmth and light to germinate well, and fresh seed is usually soaked or leached in water for one to several days before sowing.
Best at about 35 °C (95 °F): over 90% germination, against 71-74% at 20-30 °C (68-86 °F).
On the surface or barely covered; the seed needs light.
About 7-8 days at 35 °C (95 °F); up to 21 days in cooler conditions.
Required: the seed is light-sensitive and germinates less in darkness.
Soak or leach fresh seed in water for 1 to several days, changing the water daily.
Usually raised in a nursery bed and transplanted at about 40 cm (16 in).
Henna seed is tiny (about 3 mm across, roughly 700,000 seeds per kg) and orthodox: dried to about 5-7% moisture it keeps its germination for at least 2 years at room temperature. Freshly harvested seed is partly dormant; this dormancy fades naturally after about 6 months of dry storage.
Not needed. Nicking or rubbing such small seed is impractical; soaking or leaching does the same job.
Not needed. In laboratory tests a 2-day chill at 5 °C (41 °F) of moist seed did raise germination of fresh seed slightly, but a water soak works as well and is simpler.
Traditional growers steep the seed in water for 3-7 days, changing the water daily, then keep it in small moist, warm heaps for a few days until the seeds swell. In ICAR-IARI tests, simply leaching fresh seed in running water for 24-48 hours raised average germination from 81% to about 87%. For home sowing, a soak of 24-48 hours in water changed at least daily is enough for most seed; sow as soon as the seeds swell.
Henna needs high temperatures. Fresh seed reached 93-95% germination at 35 °C (95 °F) or with alternating 20/35 °C (68/95 °F), against 71-74% at constant 20-30 °C (68-86 °F). In India sow in the hot months before the monsoon; in cool climates use a heated propagator.
Scatter the soaked seed thinly on the surface and press it in, or cover it with only a dusting of fine sand. Seeds buried deeply stay in the dark and germinate poorly.
A light, sandy, well-drained mix; henna prefers sandy soil.
Keep the surface constantly moist for the first days after sowing; in the field this often means watering every day.
Henna seed is positively photoblastic: germination tests are run in light because darkness reduces germination. Keep trays in bright light, not in a dark cupboard.
About 7-8 days at 35 °C (95 °F), and up to 21 days at lower temperatures. In a Madurai seed-priming trial, untreated seed emerged in about 6 days with 76% germination.
Grow seedlings on in the nursery until they are about 40 cm (16 in) tall. Cut them back to about 15 cm (6 in) and transplant them, ideally just before or early in the rains so they establish quickly.
Water young plants and protect them from browsing animals until they are well rooted. For a hedge, plants can stand as close as 15 cm (6 in) apart in the row.
Cause: fresh, still-dormant seed sown dry, or sown in cool weather. Fix: soak or leach the seed first and sow when temperatures are high; seed stored for about 6 months germinates more evenly.
Cause: henna seed needs light. Fix: sow on the surface or cover with only a very thin layer of sand.
Cause: tiny seedlings in a hot, sandy bed lose moisture fast. Fix: water lightly every day until plants are established.
Cause: black root rot and bacterial leaf spot have been reported from western India, mostly where soil stays wet. Fix: use well-drained soil and avoid waterlogging.
Henna needs high temperatures for germination, growth and development. It tolerates low humidity and drought, so it suits hot, dry regions of India.
Sandy soils are best, but henna also grows on poor, stony and clay soils across a wide pH range.
Commercial plantings are usually cut twice a year from the second year, starting when flower buds begin to form. In the first year, cut about 5 cm (2 in) above the ground.
Henna can also be grown from branch cuttings with 6-8 buds, which is useful to multiply a plant with good leaves.
Grow henna from seed for a hardy, heat-loving hedge and your own dye leaves.
Traditionally 3-7 days with the water changed every day. Research found 24-48 hours of leaching in running water already improves germination of fresh seed. Sow as soon as the seeds swell.
The usual reasons are cool temperatures, seed buried too deep (it needs light) or fresh dormant seed sown without soaking. Germination is best at around 35 °C.
Yes, as long as it gets full sun, warmth and a free-draining sandy mix. Regular cutting keeps it bushy.