Start indoors or direct sow?

Start indoors and transplant in short or moderate growing seasons, using biodegradable pots or careful handling because cucurbit roots dislike disturbance. Direct sow in warm regions after the soil is thoroughly warm.

When to start Bitter Melon seeds

Start indoors 3 to 4 weeks before the last spring frost, but do not transplant until 2 to 3 weeks after frost when weather is warm. Direct sow 2 to 3 weeks after the last frost, when soil is at least about 70 F.

How to sow the seeds

Sow one seed 1/2 to 1 inch deep in a 3 to 4 inch biodegradable pot filled with sterile, well-drained seed-starting mix. Keep the pot warm and provide bright light as soon as seedlings emerge.

Germination

Seeds often sprout in 7 to 14 days, though hard seed coats can make germination uneven. Warm, evenly moist soil around 75 to 85 F is ideal, but do not keep it saturated.

Seedling care

Give seedlings a grow light close enough to prevent stretching and water only when the mix begins to dry at the surface. Keep one strong seedling per pot, use clean containers, and provide airflow to reduce damping off.

Transplanting & hardening off

Harden plants off for 7 to 10 days and transplant only after warm weather is settled. Disturb roots as little as possible, plant at the same depth, water well, and install a trellis or other support.

Tips

Use fresh seed, as older bitter melon seed may germinate poorly. A seedling heat mat can make a major difference when indoor temperatures are cool.

General seed-starting guidance for US home gardens; timing depends on your local frost dates and variety. Page updated Aug 4, 2026.