Germination temperature
Warm; laboratory tests use about 25 °C (77 °F).
Herb growing guide
Kalmegh is a fast, bitter-leaved annual herb native to the Indian subcontinent, harvested about four months after sowing. Its small seed has a hard coat, so a simple pre-treatment and a warm, moist nursery make the difference between a sparse and a full tray.
Warm; laboratory tests use about 25 °C (77 °F).
Very shallow; cover the small seed with only a dusting of fine soil or sand.
About 8-10 days in a nursery; most seed sprouts by day 3-6 in good lots, with final counts by about day 18.
Full sun to partial shade for a few hours a day.
Recommended: hard seed coat. Hot water at 50 °C (122 °F) for 5 minutes, or a gentle rub with fine sandpaper.
Usually nursery-raised and transplanted at about six weeks; direct sowing is possible.
Germination varies widely between seed lots. In nursery trials of Indian genotypes it ranged from 21% to almost 98%, and seed stays viable for about one year after harvest, so use fresh seed and sow a little more thickly than you need.
Helpful. Kalmegh seed has a hard coat that blocks water uptake (physical dormancy). In a 2026 Malaysian study, rubbing seed lightly between two sheets of fine (P120) sandpaper for five circular strokes raised germination to 93%, compared with about 7% for untreated seed. Rub gently: the aim is to scuff the coat, not crush the seed.
Not needed. Kalmegh is a warm-season crop and cold treatment does not address its hard seed coat.
A hot-water soak is the common Indian treatment, but sources differ on how much it helps. In a Tamil Nadu study, hot water at 50 °C (122 °F) for 5 minutes raised germination from 62% to 84% and was rated the best low-cost treatment. The Malaysian study used the same 50 °C, 5-minute treatment and got only about 18%, far below sandpaper. National Medicinal Plants Board (NMPB) practice also soaks seed in plain water for 24 hours before nursery sowing. If seed comes up poorly after hot water, try sandpaper next time. Never use boiling water.
Warm. Germination studies were run at 25 °C (77 °F). In India the nursery is sown in warm weather; elsewhere, sow indoors in late spring or use a heat mat.
Sow on the surface or barely covered, in lines about 5 cm (2 in) apart in a nursery bed, and press lightly so the seed touches moist soil.
NMPB uses a nursery mix of soil, sand and organic matter in equal parts (1:1:1). The field crop likes medium-fertile sandy loam to clay loam.
Keep the surface evenly moist but not soggy until seedlings are established; a light cover or regular misting helps tiny seed.
Bright light after emergence. The Malaysian tests germinated seed under a 16-hour light period.
NMPB gives 8-10 days in the nursery. In Indian genotype trials most seeds sprouted between days 3 and 6, and the whole germination period lasted about 6-16 days depending on the seed lot.
Transplant six-week-old seedlings, 10-25 cm (4-10 in) tall, at about 30 x 15 cm (12 x 6 in). Water lightly after planting.
Weed at about 20 and 60 days after transplanting; kalmegh is small at first and easily overgrown. If direct-sowing, thin to the same spacing.
Cause: hard-coated (physically dormant) seed that cannot absorb water. Fix: scarify lightly with fine sandpaper or give a 50 °C (122 °F), 5-minute hot-water soak before sowing.
Cause: kalmegh seed stays viable for only about a year. Fix: sow seed from the latest harvest.
Cause: weeds outgrow the small, slow early plants. Fix: start in a nursery and weed the field twice in the first two months.
Cause: rubbing too hard, or water that was too hot. Fix: use light pressure and a thermometer; 50 °C (122 °F) is hot to the touch, not boiling.
Kalmegh grows in tropical and subtropical conditions across India and tolerates a few hours of shade, but it is grown in open fields.
NMPB practice gives only 4-6 light irrigations up to harvest.
The crop is ready about 120 days after sowing, when most plants are in bloom. Cut whole plants, dry them two days in the sun and then in shade.
NMPB describes kalmegh as hardy, with no notable pest or disease attack in trials; good drainage and clean beds are usually enough.
Scuff the seed, sow it warm, and harvest kalmegh in about four months.
The seed coat is hard and keeps water out. Light sanding or a 5-minute hot-water soak at 50 °C (122 °F) breaks this; untreated seed gave as little as 7% in one study.
It helped in a Tamil Nadu study (62% to 84%), but in a Malaysian study gentle sandpaper scarification worked much better (93% vs 18%). Try sandpaper if hot water disappoints.
About 120 days. Harvest when most plants are flowering.