Margaret Lauterbach

How to heat and cool your greenhouse in the winter

Look familiar? If you have these in your garden, the coming cold weather doesn’t mean you have to give up on them ripening.
Look familiar? If you have these in your garden, the coming cold weather doesn’t mean you have to give up on them ripening. MCT

The cost of greenhouses has lowered quite a lot, and if you’ve bought one, you face the problem of heating and cooling it in winter.

You can physically open windows at or near the roof to let heat escape if you don’t want to hire an electrician to set up thermostat controls and an exhaust fan, but heating it on cold days is a different problem. has several clever ways to heat areas using tiny tea lights and flower pots in specific configurations. On the youtube site, search for <tea light heater>.

Our winter sun is quite bright and hot enough to raise the interior temperature of a greenhouse to over 100 degrees, even when there’s a foot of snow on the ground. Lest you cook your greenhouse plants, your greenhouse does need cooling, even in winter. If you’re new to this area, our winter sun appears fairly low in the south, so situate your greenhouse to take advantage of that.

Straw bales make great mouse houses

If you grew plants in straw bales this year, be aware they make great mouse houses, warm and cozy for those four-footed predators. If you don’t want to shelter them, deconstruct the bale, adding it to your compost pile. In my yard, at least, mice and voles haven’t used the compost pile for winter shelter. In spring mice can and will feed on tiny seedlings, foiling your efforts to raise specific varieties of plants for your own use. They’re quite destructive in the garden.

Winterizing your garden involves tending to your compost pile. Ideally, turn it and turn a hose on it for a bit. Then have your sprinklers blown out before we have a freeze that breaks your sprinkler system.

Some folks use spray products to repel spiders this time of year too. Spiders are valuable workers in your garden, so there’s really no need to spray there or around the perimeter of your yard. If you don’t want them in your house, spray around the foundation only. Spraying the perimeter of the yard may kill ground-dwelling bees and other helpful creatures, in addition to the micro-herd in your soil.

grow winter crops or preserve what you have?

At this time of year, those of us who grow food gardens have more produce than we can consume, and we’re on the brink of days too cold for much food production, so we’ve got to preserve what we have or buy our food. We can grow some freeze-tolerant crops through the winter, since our winters now are fairly tolerable. Some brassicas, spinach, arugula and other greens shrug off chilly temperatures, but preservation of crops such as tomatoes means we can or dehydrate those fruits to consume during winter months.

If your tomato plants are still alive with green fruit on them, you can pull the plants and hang them in an area free of frost, picking tomatoes as they ripen or pick green tomatoes and store them in shallow boxes (no more than about two layers) indoors, away from direct sun. The former method is best for small salad tomatoes such as cherry tomatoes.

If you leave root crops such as carrots, beets or potatoes in the ground, some insects will damage them over winter, and hard freezes will split and further damage them. You can protect them to some extent from freezing with abundant mulch. Digging carrots or beets before the ground freezes is preferable, and you can store them in your refrigerator hydrator for a very long time, using green plastic bags made for long-term food storage. The brand I’ve used is Debbie Meyer.

Send garden questions to or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.