Our gardening expert on the best way to steal a march on spring
To own a heated propagator is to steal spring’s best hand and play it out in winter, to trick seeds deep in dormancy into thinking the weather outside is not furious and fierce because the soil inside is deliciously warm, and the air is moist.
Germination is fast if soil is a constant temperature. It’s fairly easy to achieve this in the day by starting seeds off on a windowsill or somewhere sunny indoors, but even indoors, the temperature will drop considerably at night. Steady, even germination comes when day- and night-time temperatures do not fluctuate wildly, and this is most easily achieved with a heated propagator. Basic heated propagators are pre-set to 15C-21C, which is the preferred germination temperature of many tender garden plants. More sophisticated propagators have a thermostat and a soil thermometer to check the settings. Most propagators require a background temperature of about 5C, but preferably 10C in order to maintain a compost temperature above 15C.