Secret Jardin - Heating Mat 20W

A 20 watt heat mat of 55 by 35 cm, to place under a tray or propagator. Splash proof to IP64, with a 1.5 metre cable.

Why heat from below rather than above

For germination and cuttings the temperature of the medium matters more than the temperature of the air, and that is not obvious.

A seed responds to the warmth around it in the soil, not to room temperature. The same holds for a cutting: the roots that have yet to form will form in the medium. Heat the air and the medium follows only much later, and a wet pot stays structurally cooler than the air above it through evaporation.

A mat under the tray reverses that. The heat goes straight into the medium and the root zone runs some 5 to 10 degrees above ambient. That is precisely the range in which germination and rooting accelerate.

There is a second effect. A warmer medium under cooler air lets moisture evaporate faster at the surface, so you are less likely to keep a permanently wet layer in which cuttings rot.

Lay the mat flat without folds, and do not stand a tray with a thick insulating base on it. A layer of air under the tray blocks the very heat you want to pass through.

Technical Specifications:

• Power: 20 watts
• Mat size: 55 x 35 cm
• Voltage: 230 volts
• Cable length: 1.5 metres
• Protection: IP64, splash proof
• Heat output: about 5 to 10 °C above ambient

Frequently asked questions

Does it have a thermostat?
No, the mat heats continuously. To regulate it you need a separate thermostat.

Can it get wet?
It handles splashes. Not immersion or standing water.

Will my propagator fit?
The mat is 55 by 35 cm. A smaller propagator works too; you simply do not use the whole surface.