Warm sheltered site
Seed of most species does not need light to germinate. But once germinated, the tiny seedlings need gentle light, and in the wild are generally sheltered from full sun and drying winds by features such as bushes, tussocks, trees and logs.

Place the trays in a warm sheltered spot with 50 to 80 per cent shade away from such threats as hens, pups, footballs and livestock One of the following sites is often suitable: an area beneath shrubs which receives shade and dappled sunlight, a small shelter covered with shadecloth, a glass-house or a sunny room. As fungal diseases can be spread by water, avoid standing the trays on damp soil or where water collects.

A site which is too shady may produce weak seedlings and encourage plant diseases. Good ventilation reduces the likelihood of fungal disease.

Once or twice a day and more often in very hot weather, water the trays by bottom-watering or a fine spray. Keep the mix always moist and do not let it dry out - avoid go-stop-go germination. If the mix dries out after seed begins to sprout, many seedlings will die.

But avoid over-watering and long periods of sodden mix as this could lead to heavy losses from diseases due to fungi. For the same reason, avoid splashing muddy water on to the trays. In hot, sunny weather, if watering in the open with a spray, apply water in the morning or late afternoon, as water sprayed on leaves around mid-day may heat
up in strong sunlight and scald the plants.

Check trays regularly for germination, and be prepared to take quick action at the first sign of disease or attack by pests such as slugs.

A sowing mix temperature of 20 to 25 C is ideal for germinating seed of most native trees, although 15 to 20 or even cooler is ideal for some species, and some tropical species prefer 25 to 35. Each species has an optimum temperature for germination but can tolerate considerable variation around this.

If you want to check temperatures accurately, buy a small horticultural thermometer and stand it up in the sowing mix with its bulb buried. Or place a maximum-minimum thermometer next to the trays to see how the temperature changes from night to day and from one day to the next.

If nights are cool, bring the trays into a warm room or shed at night, or cover them with a tarpaulin or bags laid over a light frame or an upturned box. Artificial heating allows seeds to be germinated even in winter. A small propagation unit warmed by electricity can be bought and can produce batches of up to 200 or 300 seedlings.

Alternatively, obtain a polystyrene vegetable box with sides level at the top, and also a sheet of 6 mm glass slightly larger in size than the top. Stand the box in a sunny spot, place the germination trays in it and lay the glass sheet on top. Use a small piece of wood to raise one end of the sheet about 5 mm off the box top.

Check temperatures in the box with a thermometer to avoid over-heating, and raise or lower the temperature by changing the space between glass and box. A piece of shadecloth laid over the glass can also reduce temperatures. Be especially watchful for that sudden unusually-hot day which can overheat and kill plants.

Use of fertiliser
Seedlings in germination trays generally grow steadily without fertiliser, but once a week a complete water-soluble fertiliser can be sprayed on the leaves from a hand spray or added to the water used for bottom-watering. If spraying the leaves, spray during early morning or late afternoon to avoid burning the leaves.

Don't over-fertilise: more is not necessarily better.