Strong seedlings are half the harvest. In Mauritius the challenge is not cold — it is humidity, heat, and the fungal pressure that comes with both. This guide covers raising transplants that survive the move to the garden.
The Setup
- Cell trays (50-cell trays suit most vegetables) — cells dry evenly and roots come out intact.
- Medium: 60% cocopeat + 40% fine sifted compost. Never garden soil in trays — it compacts, drains badly, and carries damping-off fungi.
- A bench or table off the ground: better airflow, fewer snails, kinder on your back.
- Bright light from day one. A seedling stretching for light in a dark corner is ruined in 48 hours.
Sowing
- Fill trays and press the medium down lightly — airy but not loose.
- Sow at a depth of roughly twice the seed's size; tiny seeds (lettuce, brèdes) barely covered.
- One or two seeds per cell; snip the weaker one later with scissors — never pull it out.
- Water with a fine rose or a spray — a jet of water excavates seeds.
- Label everything. Every grower who skips this regrets it within two weeks.
Season Adjustments — This Is the Mauritian Part
Summer (November–April):
- Midday sun cooks black seedling trays. Give trays morning sun and afternoon shade, or 30–40% shade cloth.
- Lettuce and coriander germinate poorly above about 28°C — start them in the coolest, shadiest spot you have, or wait for winter.
- Daily storms waterlog trays left in the open; keep them under cover you can move.
Winter (May–October):
- On the plateau, germination slows in the cool — be patient, and give trays the sunniest spot available.
- Almost every vegetable germinates happily; this is the big seedling season.
Damping-Off: The Humid-Climate Killer
Damping-off is a fungal attack that fells germinated seedlings at the soil line — one day standing, next day collapsed. In our humidity it is the number one seedling disease. Prevention is everything:
- Water in the morning so the surface dries by evening.
- Airflow, airflow, airflow — space the trays, never crowd them in a closed corner.
- Use clean trays (wash used ones) and fresh medium, never recycled soil.
- Do not overwater: moist, not soaked, and let the surface dry slightly between waterings.
- Remove any collapsed seedling and its neighbours immediately.
Hardening Off
Seedlings raised in comfort collapse in a real garden bed unless you toughen them first:
- A week before transplanting, move trays into more direct sun and wind, a little more each day.
- Reduce watering slightly in the final days.
- Transplant in the late afternoon or on an overcast day, water in immediately, and mulch.
When to Transplant
- Most vegetables: when they have 3–4 true leaves and roots hold the cell plug together.
- Overgrown seedlings root-bound in tiny cells never fully recover — sow less, more often, instead of one giant batch.
Quick Problem Guide
- Poor germination — old seed, medium too cold (plateau winter) or too hot (summer): test-germinate 10 seeds in damp tissue paper to check the seed lot.
- Leggy, pale seedlings — not enough light: move them the same day, and pot tomatoes deeper to bury the stretched stem.
- Collapsed at soil line — damping-off: see above, act immediately.
- Purple or yellow leaves — hungry: the compost fraction was too low; feed with weak liquid fertiliser.
Module 2 of the free Grower Academy covers seedling raising and transplanting in full.