How to Use Cold Frames As a Year-Round Gardening Tool
Springtime sees your friendly, think-ahead Planet Natural blogger putting his cold frame to heavy use. Now, in a time of year where frosts are still possible, many of our indoor vegetable starts are almost ready to go into the garden. They need to get use to being outdoors. Many of them can’t survive the night-time cold but can when protected inside a cold frame, maybe draped with a blanket on the coldest nights.
It’s also the time of year we’ve also run out of room under our indoor grow light and need a place to keep vegetable starts where they’ll get more sunshine than they would on a window sill. And we also want to get a head start on some of our long-season plants, like tomatoes, peppers or winter squash.
Can you see why we’re thinking a second, and maybe a third, cold frame might be a good—make that great—idea?
And don’t forget flowering plants. You can get a big jump growing pansies by starting them in pots inside a cold frame.
But cold frames aren’t just an amazing accessory to your spring-time gardening. They’re good for a number of uses all year ’round:
- Cold frames are a good place to store potted plants and cold-sensitive bulbs and root-cuttings (buried in sawdust or straw) during winters in areas where night-time temperatures aren’t consistently extreme (near and below zero).
- Cold frames are a good place to make late fall plantings of such cold hardy plants as broccoli, kale and spinach, which can be over winters in a cold frame—plant them right in the ground–and can even provide early spring and mid-winter harvests during warm spells. Fresh greens in February? Yeah!
- Cold frames are a great place to start vegetable seeds in pots ahead of gardening season.
- Cold frames are great for hardening off your vegetable starts as they provide warmth (even with the tops up), protect against excess wind, and offer warmer over-night temperatures.
- Cold frames are an ideal place to sow squash seed or set out tomato plants once there’s room. They’ll give these long season vegetables a warm, jump start. By the time they’re pushing up against the cold frame’s top, just leave the tops off.
- Cold frames are great places to plant greens in late summer and hold them well past the first frosts of fall … and maybe longer.
When locating a permanently-placed cold frame, make sure the soil drainage is good. This might require digging up the soil to a depth of two or three feet and putting in a six-inch layer of pea-gravel or small river rock to facilitate water conduction before laying down compost and soil. If you’re only using your cold frame for potted plants and starts, you can just dig up six inches of soil and add a gravel surface. The gravel or tile or stone will serve as a heat sink, carrying the day’s accumulated warmth into the night. We’ve seen a cold frame in which the gardener set concrete block in sideways, then filled the spaces with gravel to provide a heat-retaining surface.
Placing your permanent cold frame against the south or west-facing side of a building will also help it gather and retain heat. The building will also shelter your cold frame from the wind. Here are examples of permanent cold frames (brick!) incorporated into the sides of buildings. Our cold frame was against a white garage wall which gave the tomatoes we grew there an extra warm and sunny boost throughout the summer, just what they needed in short-season Montana.
Covering your raised garden bed with plastic or some other type of light-conducting shelter can turn it into a wonderful cold frame.
Cold frames that sit on top of the soil and are moveable can travel from place to place as you plant different, heat-loving vegetables. You can build a cold frame that’s transportable or construct a make-shift one of hay bales, which are especially good insulators, by placing them in a square or rectangle just big enough to support old window frames with glass or a shower door. They’re also available as kits and can even be made of convenient materials that make them lightweight and functional as tents.
You can turn your cold frame into a hot box by adding rotting manure or a layer of leaves or straw seasoned with microbe-rich compost beneath your soil layer. The heat generated by the decaying organic material will help hold plants over winter as well as give soil temperatures a boost in time for spring germination. One gardener we know reported great result using a layer of alfalfa pellets and some compost instead of straw or leaves (which tend to compact … chop them first).
Here’s a comprehensive guide to using cold frames—with building plans—from the University of Missouri. We’d really like to hear about your cold frame—how it’s built, where it’s located, how you use it.
One warning about cold frames … they can get hot when the sun’s shining! Be sure to ventilate your cold frames by lifting the lids and propping them open—or removing them all together—on sunny days. It’s an unpleasant surprise to come home from work at the end of the day and find your lettuce starts baked beneath the glass or plastic of your cold frame.
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One of nature's epic events is underway: Monarch butterflies' fall migration. Departing from all across the United States and Canada, the butterflies travel up to 2,500 miles to cluster at the same locations in Mexico or along the Pacific Coast where their great-grandparents spent the previous winter.
Millions of People Care About Monarchs<p>I will never forget the sights and sounds the first time I visited monarchs' overwintering sites in Mexico. Our guide pointed in the distance to what looked like hanging branches covered with dead leaves. But then I saw the leaves flash orange every so often, revealing what were actually thousands of tightly packed butterflies. The monarchs made their most striking sounds in the Sun, when they burst from the trees in massive fluttering plumes or landed on the ground in the tussle of mating.</p><p>Decades of educational outreach by teachers, researchers and hobbyists has cultivated a generation of monarch admirers who want to help preserve this phenomenon. This global network has helped restore not only monarchs' summer breeding habitat by planting milkweed, but also general pollinator habitat by planting nectaring flowers across North America.</p><p>Scientists have calculated that restoring the monarch population to a stable level of about 120 million butterflies will require <a href="https://doi.org/10.1111/icad.12198" target="_blank">planting 1.6 billion new milkweed stems</a>. And they need them fast. This is too large a target to achieve through grassroots efforts alone. A <a href="https://www.fws.gov/savethemonarch/CCAA.html" target="_blank" rel="noopener noreferrer">new plan</a>, announced in the spring of 2020, is designed to help fill the gap.</p>
Pros and Cons of Regulation<p>The top-down strategy for saving monarchs gained energy in 2014, when the U.S. Fish and Wildlife Service <a href="https://www.fws.gov/southeast/pdf/petition/monarch.pdf" target="_blank">proposed</a> listing them as threatened under the Endangered Species Act. A decision is expected in December 2020.</p><p>Listing a species as endangered or threatened <a href="https://www.fws.gov/endangered/esa-library/pdf/listing.pdf" target="_blank">triggers restrictions</a> on "taking" (hunting, collecting or killing), transporting or selling it, and on activities that negatively affect its habitat. Listing monarchs would impose restrictions on landowners in areas where monarchs are found, over vast swaths of land in the U.S.</p><p>In my opinion, this is not a reason to avoid a listing. However, a "threatened" listing might inadvertently threaten one of the best conservation tools that we have: public education.</p><p>It would severely restrict common practices, such as rearing monarchs in classrooms and back yards, as well as scientific research. Anyone who wants to take monarchs and milkweed for these purposes would have to apply for special permits. But these efforts have had a multigenerational educational impact, and they should be protected. Few public campaigns have been more successful at raising awareness of conservation issues.</p>
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="91165203d4ec0efc30e4632a00fdf57d"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/KilPRvjbMrA?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
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A Model for Collaboration<p>This agreement could be one of the few specific interventions that is big enough to allow researchers to quantify its impact on the size of the monarch population. Even if the agreement produces only 20% of its 2.3 million acre goal, this would still yield nearly half a million acres of new protected habitat. This would provide a powerful test of the role of declining breeding and nectaring habitat compared to other challenges to monarchs, such as climate change or pollution.</p><p>Scientists hope that data from this agreement will be made publicly available, like projects in the <a href="https://www.fws.gov/savethemonarch/MCD.html" target="_blank">Monarch Conservation Database</a>, which has tracked smaller on-the-ground conservation efforts since 2014. With this information we can continue to develop powerful new models with better accuracy for determining how different habitat factors, such as the number of milkweed stems or nectaring flowers on a landscape scale, affect the monarch population.</p><p>North America's monarch butterfly migration is one of the most awe-inspiring feats in the natural world. If this rescue plan succeeds, it could become a model for bridging different interests to achieve a common conservation goal.</p>
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