The following sowing and transplanting methods are available to the amateur gardener who wants to grow tomatoes outside without the use of a greenhouse.
Tomato seeds can be sowed directly into a seed bed. However, this is by far the riskiest method in temperate climates. It is only suitable for those areas which have a last frost date in MARCH. In all other areas, the soil is unlikely to be warm enough at a time which will allow the tomato plant to develop and fruit. The soil temperature must be at least 15C (60F) at the time of sowing and during germination. It is possible to utilize a cloche or cold frame. This will warm the soil prior to planting and protect the plants in their early stages.
Using a trowel, dig a shallow drill 2.5cm deep (1in) deep in the prepared bed. Place two seeds every nine inches in the drill and cover the seeds to a depth of 2.5cm (1in). Water well if the conditions are at all dry.
The seedlings should emerge in about 10 days. When they are 5cm (2in) tall, thin to one plant every 45 to 60cm (18 to24in).