Gardening Tips: Greenhouse-Keeping

Editor’s Note: This column first appeared on 28 March 2018.


What to do this week

If you have a greenhouse, that perfect place that will be housing some of those seedlings from the crowded windowsills very soon, this week is a great time to get it cleaned up and organized. You may have done that in the fall. I didn’t. This week will be my time to clean the old plant trays, pick up little bits of broken pots, and clear off the shelves, so I will be ready when spring hits. I am expecting to be able to put some of the hardier seedlings out in the greenhouse within a week or two, so I had better get to it.

Some people plant in the ground within the greenhouse. I tend to use pots and planters, and there is a bit of work to do to organize them for this year’s use. Some of the planters need to be weeded so that the unwanted plants don’t spread to the new crop. I’ll also be checking the plastic greenhouse covering to be sure there isn’t a bit of mending needed here and there. Now is the time to do all of your greenhouse maintenance work, as soon it will be full of life.

A small self made greenhouse at Fir Lane, Lowestoft, Suffolk (Photo by Tim Parkinson (Flickr) [CC BY 2.0 (], via Wikimedia Commons)

Homemade greenhouse at Fir Lane, Lowestoft, Suffolk (Photo by Tim Parkinson, Flickr, CC BY 2.0, via Wikimedia Commons)

Last week I mentioned that it was time to start the seedlings for your warm summer crops. If you haven’t gotten to that, now is the time to get those tomato, eggplant and pepper seeds started. Soon these newer seedlings will be needing that windowsill space now occupied by onions, but if you are lucky enough to have a greenhouse, you will be starting onion rotation to the greenhouse very soon. (The other seedlings will join them, but not for at least a month.)

If you don’t have a greenhouse, you might be interested in spending some time this week constructing a cold frame. It isn’t difficult, and can be a very good introduction to greenhouses. A cold frame is really just a very small greenhouse.

You can build your first cold frame if you have a few boards lying around that would work as a raised bed frame. You won’t be filling it with soil as your plants will need that height for growing. You can experiment with a rather small frame to start. The size of an old window sash you might also have in the garage or basement would be perfect. That window will become the roof. It will let in light and warmth, but protect against the cold and wind.

It is a good idea to set up your frame so that the window sash is slanted, but that isn’t necessary. You will just have to be careful if there is snow, as the snow will collect on the flat window surface and can cause it to break. Connect the window frame to the box with a hinge on one side. That way you can easily prop it open on those really warm days. The interior of a cold frame is a very small space, so it heats up quickly on a sunny day even if you still feel chilly going out to check on it. Keep an eye on those little plants. Just prop the window up on one side to let the air circulate.

Beginner gardeners sometimes feel shy about putting plants out in what seems like the cold. Most plants need warmth to germinate, with the notable exception of spinach, but once they are growing they can handle much more temperamental conditions. It will still be a bit cool for warm summer plants like tomato and pepper, but onions and kale, salad greens, and cold crops like cabbage, broccoli, cauliflower and Brussels sprouts can be put out as soon as the nights are reliably above freezing. Even a minus 1 or 2 degree night is not a crisis in a greenhouse or cold frame. If you are expecting a really cold snap of a night, you can cover a cold frame with a blanket, and just leave a light bulb burning in the greenhouse. That will get them through.

It is a bit early to put things out yet, but it won’t be long at all, so get that greenhouse cleaned up, or that cold frame built. It will be a great long weekend project.





Market gardener, farmer, workshop leader, seed-saver, political candidate and mother, Michelle Smith has spent over 30 years coping with the challenges of our bioregion and in the process has built a store of practical and technical knowledge. The Inverness resident has served on the board of Seeds of Diversity Canada and represented Alternative Producers with the Federation of Agriculture but can do nothing about her hair. She is pictured with a head of Club Wheat, a seed that shares her approach to hairdressing.




Backyard food gardener Madeline Yakimchuk caught the food-security bug in the early ’90s through Cuba’s Urban Agriculture Department, taking her first permaculture course and planting her first garden. She can often be found discussing food security, nurturing a plant-based lifestyle or trying to give away vegetables. Professionally, she is GRYPHON media productions but sometimes uses la bruja in her volunteer work, most notably in managing the garden column, which begins life as a telephone interview.





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