Natural Life Magazine

Time to Power Down Your Greenhouse Heater

Time to Power Down?
By John Walker

In this extract from his new book Digging Deep in the Garden: Book One, John Walker asks whether, amid growing climate chaos, we can really afford, morally or financially, to keep powering up our propagators and greenhouse heaters. He also provides some earth-friendly alternatives.

For the youngest to the oldest gardener, the novice to the expert, one captivating, enduring, and miraculous activity shines out: growing plants from seed. When you stop to ponder how those piles of pumpkins, heavy bunches of carrots, or basketfuls of ripe tomatoes all start out as seeds, the realization is humbling. When we sow seeds, the worst we can expect if things go wrong and the seeds fail to germinate is disappointment. We can try again and hope for better luck, but life goes on. In some parts of the world, if seeds fail to germinate, or crops fail to establish, those who sowed them could face death. If their seeds don’t come up, they don’t nip to the garden center for another packet – they start living on food aid.

The prospect of having to rely on what your own garden or allotment produces, for your very survival, ought to send a shudder down the spine of even the expertly self-sufficient gardener. Can you begin to imagine watching your seedlings wither and die, in the sure knowledge that sometime soon you will be relying on food handouts? And will you entertain the thought that, in order to give your own seeds the best start in life, you might actually be condemning fellow gardeners in other parts of the world to a life of grim dependency – or worse? Hence the terrible irony writ large across the front cover of a magazine here on my desk: “Greenhouse heating: What is the true cost of protecting your crops?” The actual title of the article is equally ironic: “Heating: A high price to pay?”

Predictably, the article is actually a consideration of the different fuels available for running propagators and heating greenhouses – electricity, gas, and paraffin, all of which release carbon dioxide, either through their generation or when they are burnt, as gas and paraffin are, at the point of use. The main focus of the article is on the costs of using different fuels and the types of heater available. A few brief paragraphs at the end do discuss being “environmentally friendly,” with the admission that to be completely “green” you shouldn’t heat a greenhouse at all.

The carbon dioxide produced by a gas- or paraffin-fired heater is a greenhouse gas in every sense. It respects no international boundaries; heating your greenhouse contributes directly to the global greenhouse effect. We can no longer afford to count just the economic cost of nurturing our seeds or cuttings – we need to turn the price tag over and look at the environmental and human costs.

I haven’t used a heated propagator, or heated a greenhouse other than to give minimal frost protection in extremis, for years. Nor does it worry me that I may never do so again. That’s bad news, I know, for the manufacturers of greenhouse gardening equipment, but business as usual cannot continue. It would be good news for the planet, and it might just help ease the burden on those who depend on their gardening to stay alive.

If you really can’t resist the urge to twiddle the thermostat dial in the coming months, at least keep it at minimum, turn it off when possible, and switch, if you’re using electricity, to a renewable supplier. This will at least help us, here in the energy-obese developed world, to tighten our belts. Better still, forget energy-intense artificial heating and make better use of what warm places you already have, or cut to the chase and tap directly into the sun.

One of the most effective propagators I’ve used, powered entirely by natural and renewable energy, is an empty compost bag turned inside out, so the heat-absorbing black side faces out. I simply slip trays or pots of seeds inside it and stand them on the sunny bench of an unheated greenhouse, polytunnel or lean-to, or in a sunny porch. Failing that, commandeer a sunny window-sill, or use a sheltered south- or west-facing wall or window-ledge. The sun will do the rest, even on cloudy but otherwise bright spring days. Simpler still, slit the bag open and lay it over your sown containers, black side up. Go put your hand into an empty inside-out bag on a sunny day and feel what I mean.

Don’t expect the same results you would get from using a heated propagator, or by heating a greenhouse to maintain a constant temperature. It will generally take longer for the seeds to come up, but come up they will. On colder nights it might be necessary to take them indoors, or to be creative with layers of fleece, cardboard, and old curtains. If you’re using a lean-to greenhouse, even a modest one, think about painting the area of wall it covers black. This will absorb the sun’s energy during the day, then act as even more of a radiator at night, especially if it’s draped in warm layers on cold nights. Switching on to sunshine, while it might not be as constant as the power flowing through a three-pin plug, or hissing from a gas bottle, costs nothing. Not even lives.

As we consider switching off our propagators and heaters, as we think long and hard about powering down our garden energy use in general, we need to throw another important switch to “on,” and that’s a switch in our thinking. We need to stop trying to beat or extend the seasons (global warming already promises us plenty of seasonal hiccups). We need, instead, to move closer to the seasons, to become more intuitive, to plan better, and to be more realistic about just what we can or can’t grow without the subsidy afforded by fossil fuels. With only a little experience we can stretch the growing season by using cloches, polytunnels and unheated greenhouses – any structure that catches the sun’s energy.

Can we really afford, financially, ecologically, or morally, to be sowing tomato seeds in early February, just so we can pick fruits in June? Waiting another month won’t bring us to our knees, and they’ll probably taste better to boot. But our impatience to have our seeds sprinting into action, at the flick of a switch or the strike of a match, is helping to fuel the destruction of crops, in distant lands, on which life itself depends.

This essay won the Garden Media Guild Environmental Award. It appears here as an edited extract from John Walker’s new book Digging Deep in the Garden: Book One (2015, Earth-friendly Books). The essays in the book were first published in Organic Gardening magazine as John's long-running ‘digging deep’ series. He has been growing things since he could walk and is an award-winning gardening and environment writer and author. He is having fun, despite some squirrel-fuelled frustration, eking a new earth- and climate-friendly garden from a once bracken-riddled hillside in Snowdonia, North Wales. Read more from John at


Copyright © Life Media

Privacy Policy 

Life Learning BookBeyond SchoolChallenging Assumptions in Education

Natural Life's Green and Healthy Homes book

Life Learning Magazine

Natural Life Books

Childs Play Magazine

Natural Child Magazine

Natural Life Magazine