March to April indoors with warmth; earlier crops need extra heat and light.
Late spring, when your greenhouse can provide suitable temperatures. Avoid cold nights.
Summer into autumn, depending on variety and conditions.
Choose the right habit
Cordon tomatoes grow as a trained main stem and need support and regular side-shoot removal. Bush tomatoes branch naturally; do not remove all their side shoots. Choose varieties to suit the height and time you have, not just a photograph of the fruit.
Sow and pot on
Sow in fresh seed compost following the packet’s temperature and depth instructions. Move seedlings into bright conditions after germination. Pot on as roots fill the container, keeping plants warm and avoiding waterlogged compost.
Water, feed and train
Use a generous container or prepared border, support stems from the start and water consistently at the roots. Begin tomato feeding when the first truss is setting fruit, following the feed label. Ventilate to manage heat and humidity.
Watch for problems
Uneven moisture can contribute to split fruit and blossom-end rot. Check root moisture before adding extra feed or calcium. Remove diseased material, inspect leaf undersides and maintain airflow. In autumn, pick remaining usable fruit before cold damage.
Plan the next step
Keep a weekly record of watering, feeding and harvests. Note your overnight minimum temperature: this is more useful than the warmest afternoon reading when deciding whether a tender crop can move into an unheated greenhouse.
Read the monthly growing calendar, watering and feeding guide and plant health guide alongside your seed packet.
Further reading: RHS greenhouse vegetables.
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