1. Soak and pre-germinate
Watermelon seed has a fairly thick coat. Soaking in lukewarm water for about 4–6 hours lets it take up water fully. Then wrap the seed in a damp cloth and keep it warm and dark; the radicle usually emerges within 24–36 hours.
Caution: the cloth should be damp, not soaked. Seed left in water too long runs short of oxygen and rots.
2. Media and trays
Use plug trays with peat or another free-draining medium. Set pre-germinated seed with the root tip pointing down and cover with about 1 cm of medium. Plug trays let you transplant with minimal root disturbance, which matters a great deal for cucurbits.
3. Nursery care
- Give full light as soon as the cotyledons open, or seedlings stretch
- Keep the medium moist but never wet — damping-off follows high humidity and still air
- Two to three days before transplanting, reduce water and increase sun exposure to harden the plants
4. When to transplant
Move to the field at the 2–3 true-leaf stage, typically around 10–14 days after sowing. Do not let seedlings become root-bound in the plug — they re-establish slowly and that delays maturity.
Transplant in the late afternoon or on an overcast day and water in immediately to limit first-day transpiration stress.
5. Count maturity correctly
Our watermelon packets state maturity after sowing — Thong Thai TT 222 at 55–58 days and Thong Thai TT 466 at 58–65 days. Count from the sowing date, not the transplant date; using the transplant date will put you about two weeks out.
Summary
When seed germinates together and seedlings are equally strong, the field ripens together and can be harvested in a single pass — cheaper in labour and usually better priced than picking over several rounds.
