Greenhouse heating and greenhouse growing advice

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A few words on the two most common forms of greenhouse heating. Paraffin and electric.

Paraffin.
The trick with these is the adjustment of the flame wick. Leave it too high and your greenhouse will look like the inside of a chimney. You need to reduce the wick height as low as possible whilst still ensuring a flame across the FULL WIDTH of the wick. Then leave it for two mins to settle, then return and readjust accordingly.

I use paraffin heaters as an emergency back up. Or as a supplement when it gets really cold. At other times I use electric.

Electric
To my mind the best are made by “Parwin Heaters”. I have no association with them but they are streets ahead of everything else available. So you will need to google them. Why are they the best?

They have the most amazingly accurate stats that will doubtless save you a fortune. I’m talking specifically about their electronic range of stats. Second, and very important, the user can easily access the electric elements (1KW each) and even remove them and STILL use the heater. So, if an element does go they will send you another element while you are still able to use the heater (with your paraffin back up). I’ve had one element go in 12 years of continuous winter use.

Finally, don’t set your stat as high as most books say you must. Most plants are far more resilient than gardening authors give them credit. – E.g. I’ll never forget Gay Search showing us how to wrap up “PEROVSKIA” with straw in a London garden, I mean with a name like that couldn’t anyone at the Beeb comprehend where they might come from? They will happily come through Siberian winters of -40C!! So, for most plants +5 to +6C in the greenhouse is ample, PROVIDED their compost is ‘near arid’.

But whichever method you use. it pays to insulate with bubble wrap AND cover your most tender plants with fleece.

One final point on heating the greenhouse is to do the very opposite on occasion. That is, at every opportunity the air temperature goes above your set minimum be sure to ventilate. As an example, I’m ventilating my Bougainvillea greenhouse this very morning, just for a few hours, and I’ll be sure to close it at 2.30pm at the latest – ’cause it gets suddenly cold after 3pm.

• 11 Feb, 2009
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