When dealing with relatively large numbers of seedlings or cuttings, as happens often in the production of bedding plants, a tray may be a more suitable container than a pot.
Traditionally a seed tray is madeof soft wood and its dimensions are 14 in by in and, according to its required usage, either 2 in or 2\ in deep. These trays are now relatively expensive to purchase and their expected life is fairly short as they rot easily. However, they have the distinct advantage of being firm and rigid.
Plastic seed trays of the same basic dimensions are currently available in many different patterns. The most important characteristic is the degree of drainage permitted in these, and it is of paramount importance to ensure that this is adequate. The quality and variety of plastics used for making seed trays is extraordinarily variable; the best trays are those of a sufficiently thick quality to keep their shape when picked up at a corner and of a type not to become brittle on exposure to ultraviolet light. The advantage of plastics is, of course, their durability and that they can be readily cleaned. Plastic seed trays are also made in "half-tray" sizes measuring 6 in by 8^ in and 2 in deep.
2 Sow the seeds or cuttings once the pellets have fully absorbed the correct amount of water.
3 Plant out as soon as roots emerge through the sides of the netting.
There are many other materials such as compressed peat, processed paper and expanded polystyrene used for seed trays, but they tend to require careful handling. Some trays are disposable, which overcomes the hygiene problem but inevitably increases the cost factor. Expanded polystyrene trays with individual growing compartments for each seed or cutting retain warmth and so promote rapid growth.
As with pots, many containers such as wooden "Dutch" tomato trays, fish boxes and moulded polystyrene packaging can be substituted for conventional seed trays provided they have adequate drainage and they are properly cleaned before use.
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