How To Use A Heated Propagator

Even though it is cold outside, even snowing, late winter and early spring is an ideal time to sow many vegetables – especially those that enjoy long summers like tomatoes, peppers, and aubergine.

We have found our heated propagator to be a good investment, as it speeds up germination and makes the whole process more reliable. This means we can grow more, as there is a higher turnover of pots of our kitchen windowsill.


To get the most out of a heated propagator, it is ideal to have a warm or protective environment to move the plants on to. A greenhouse or polytunnel are ideal, but a plastic greenhouse or coldframe next to the house are alternatives.

See best selling heated propagators on Amazon UK.

How To Use A Heated Propagator

Please see our video, or if you prefer, scroll below to read on:

Our video features the Sankey Growarm 100 heated propagator. For the last couple of years it has done a good job, significantly speeding up germination times and making germination more reliable – meaning we sow less often and using fewer seeds.

Our model does not have a thermostatic temperature control to measure and regulate temperature. When the weather warms we take the plug out, preventing it getting too hot inside. Out of the box it comes with a plastic lid, two seeds trays, a capillary matt, and the base that contains the heating elements.

First step is to prepare the pots or seed trays. Avoiding homemade compost is best, as it can contain weeds. A fine crumbly shop bought compost is ideal. After filling the pots, we soak the soil using water from the outside tap – fresh water helps to avoid disease.

Next step is to wet the capillary matting under a tap, and place on the bottom of the heated propagator. The matting provides more moisture to the growing environment, but also helps to keep the bottom of the heated propagator clean.

We’re sowing tomato, pepper, and inca berry seeds, for later growing on in our polytunnel. We space out three seeds per pot, and then cover with a fine layer of vermiculite. If all three seeds germinate we will will divide and grow on in separate pots. There is no need to water for further watering as there is enough moisture in the compost.

When all the pots are prepared, the final step is to cover the propagator with its lid. Closing the vents on the propagator creates a humid growing environment ideal for germination. With closed vents, the pots do not need watering.

We place our heated propagator on a bright kitchen windowsill that only a receives about two hours sunshine a day. It is a bright location, but the lack of direct sunlight and warmth makes it an ideal spot for the heated propagator.

As soon as germination starts, we gradually open the vents a little each day to gently acclimatised the plants to normal conditions.


When the seedlings have developed true leaves, we remove them and grow them on the same windowsill but outside of the propagator. The propagator is then free for the next sowing.

See best selling heated propagators on Amazon UK

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