If you want to sow perennial flowers, tender bedding and patio plants, and/or tender vegetables (such as cucumbers, tomatoes, courgettes and so on) early next spring, you’ll need somewhere with a constant, warm temperature; between 20-25ºC is ideal.
The best place to germinate seeds and start off tender plants is in a heated propagator. It will maintain the warm, moist environment that’s ideal for rapid germination. Heated propagators are also useful for rooting cuttings.
If you haven’t got a greenhouse, you can put a propagator on a well-lit windowsill in a cool room. Some are even slim enough to fit easily onto a narrow windowsill.
One word of caution is to remember that water and electricity isn’t a good combination. If your ring mainisn’t protected by an RCD, use an RCD adaptor when using a heated propagator. Take care when cleaning the bottom tray and don’t immerse it in water.
If you fill the propagator directly with compost it could be too hot for some seedlings. Use smaller trays or pots inside the propagator and a max-min thermometer to aim for a temperature of 20-23ºC just below the compost surface. Propagators with a thermostat make it easier to set the temperature to what you require.
The temperature inside a propagator can increase rapidly on a sunny day. Try to use a windowsill that doesn’t get direct sunlight at the middle of the day. On sunny days, switch it off. A model with vents in the plastic cover will allow you to control the temperature more easily than one without.