A Healthy Greenhouse

Heated propagators

Heated propagators usually look like the better-quality unheated ones, and work in the same basic way, but have the advantage of a heating pad sandwiched into the rather thicker base. There are two types: fixed temperature and thermostatically controlled.

The fixed-temperature variety provides heat at approximately 19°C (66°F), which is ideal for germinating a range of seeds. They are generally reliable and really speed up germination of most seeds that require heat; they can mean the difference between success and failure with some of the more challenging ones. They are not expensive and are well worth the cost. Bear in mind that without a thermostatic control these propagators will provide heat even on the warmest days, so you'll need to check young plants regularly.

Don't forget
A small heated propagator is unlikely to be able to protect tender plants from frost in the greenhouse in winter.

Thermostats can go wrong. Check that your thermostat is always delivering the heat it should be by putting a thermometer inside the propagating unit.
Thermostatically controlled propagators.

The thermostat adds value but also expense to a heated propagator. These models are at least twice the price of the fixed-temperature sort for the same size, but they do have their benefits: they are more efficient, so they should use less electricity; they won't overheat your plants on a warm day; and they can be set at the precise temperature particular seeds need for germination or cuttings require to root. They are also available in larger sizes, making them suitable for overwintering a

Use a heated propagator with a thermostat for seeds that need a higher temperature to spring to life. small selection of plants if necessary. However, if you plan to go in for large-scale propagation, you might be better off making your own (see box, below).

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