Seed trays are ideal for cuttings or growing seeds until they are ready to plant out. They may also be used to hold a wide range of smaller seed trays or pots for ease of handling. Seed trays should have a system of drainage holes in the base to prevent seedlings or cuttings from becoming waterlogged. This will also enable them to be used on water or capillary matting.

Materials

Traditionally, trays were made out of wood, although these have now largely been replaced by plastic versions, which are cheaper and far easier to clean.

Trays may be made from cheap, thin plastic, suitable for one season only or from thicker, more rigid plastics, which although more expensive, may be re-used season after season. However, do take care to store plastic trays away from sunlight when not in use, otherwise they may become brittle and split.

Multi-Cell Systems

Multi-cell (or modular) systems enable seedlings to be grown in single 'cells', which ensures that their roots do not become entangled. This reduces root disturbance when plants are potted on or planted out.

There are a number of different modular styles available:

Expanded Polystyrene Trays

This system comprises of a polystyrene tray divided into a number of individual planting cells. The polystyrene insulates the compost, encouraging growth.

Plug Trays

These are strong polypropylene trays divided into individual cells into which a single seed is grown until it is ready to be planted on. The cells are usually tapered to enable plants to be popped out without damage to their fragile roots. Plug trays cost about the same amount as polystyrene versions; although they do not offer insulation for the compost, they do tend to last longer.

Rootrainers

Rootrainers are a commercial product designed to enable the gardener to grow a large number of healthy plants with strong root structures using a minimum of space. The rootrainer has a number of hinged segments, specially grooved to encourage the production of strong, straight roots. This helps to prevent the plants from becoming pot bound. The hinged design allows the plant to be removed without damaging the root system.