What Containers and Trays Should I Use for Starting Seeds Indoors?

The container you choose affects drainage, root development, and how easily you can transplant seedlings without damage. There is no single right answer — different crops suit different containers — but understanding the options helps you pick the right tool for each job.

Flat Seed Trays

Standard flat trays (typically 37×24 cm / 14×9 in) are best for sowing large quantities of small seeds like lettuce, onions, leeks, or flowers. You sow broadcast or in rows across the whole tray and later prick seedlings out into modules or individual pots. The main advantage is efficiency — one tray holds dozens of seedlings. The disadvantage is that pricking out is fiddly and root disturbance is inevitable. Always choose trays with adequate drainage holes and never let them sit in standing water.

Module Trays (Cell Trays)

Module trays divide the growing space into individual cells, typically 24, 40, or 84 per tray. Each cell houses one or two seeds. When you transplant, the entire root ball of compost lifts out cleanly — no root disturbance, minimal transplant shock. Module trays are ideal for brassicas, courgettes, squash, cucumbers, and anything that will be planted out directly after the seedling stage. Cell sizes matter: use smaller cells (3–4 cm) for brassicas and larger cells (5–7 cm) for cucumbers and courgettes.

Individual Pots

Small individual pots (7–9 cm) are the best choice for crops that will spend several weeks growing on indoors before planting out — tomatoes, peppers, chillies, and aubergines. They allow the root system to develop without competition. Biodegradable pots (coir or paper) are useful for crops that strongly dislike root disturbance; the whole pot goes in the ground.

DIY and Repurposed Containers

Yoghurt pots, tin cans, toilet roll tubes, and egg cartons all work well as seed containers. The key requirements are drainage holes and sufficient depth. Toilet roll tubes are particularly good for sweet peas, sweetcorn, and beans — the cardboard breaks down in the soil so roots are never disturbed. Rinse any food container thoroughly before use to remove residual fats or sugars that encourage mould.

What to Avoid

Avoid very shallow containers — seeds need a minimum of 5–6 cm depth to develop a proper root system before potting on. Avoid containers without drainage holes; waterlogging kills seedlings fast. Do not reuse containers from previous years without washing them in a dilute disinfectant solution first — disease spores linger in plastic and cause damping off in new sowings.