Greenhouse Basics: Starting Seeds Earlier and Keeping Them Alive
A greenhouse gives you a growing space, but an unheated structure is not a guarantee of frost-free conditions. Choose sowing dates and equipment around the crop and the temperatures you can maintain.
Separate germination from growing on
Seeds may need different conditions to established seedlings. The RHS describes crop-specific sowing and growing-on requirements; some tender crops need warmth followed by bright, frost-free space. Check the seed packet and record the conditions it specifies instead of using one national sowing date for everything.
Measure before adding equipment
- Record daytime highs and overnight lows with a suitable thermometer.
- Measure staging and tray space, including room to lift lids and reach plants.
- Check whether a propagator supplies heat or simply provides a cover.
- For powered equipment, verify the rating plate, UK electrical suitability and the manufacturer's permitted location before ordering.
Ventilation and watering need observation
Adjust ventilation to the weather and crop requirements. Automatic openers have their own operating range and response; they are not a promise that overheating or frost cannot occur. Follow the growing medium and crop guidance for watering and drainage rather than a universal daily quantity.
Browse Greenhouses & Plant Germination Equipment for structures and propagation equipment. Compare dimensions with your available space, access and maintenance needs before choosing accessories.
For summer conditions, see our shade cloth and greenhouse ventilation guide. Shading is one adjustable part of the growing environment, not a substitute for monitoring it.
Sources and further reading
Guidance checked 17 September 2026. Follow the instructions supplied with your specific product.
