Low Tunnels Vs Cold Frames

Gardening doesn’t have to be just a summertime activity, even in colder climates. If you live in a very cold winter climate, you may be able to go a couple of months without your soil drying out. If you want, build your cold frame over an existing garden bed and plant directly into the soil, or build it on any level patch of ground and place flats of potting soil inside for starting summer seedlings. You will need to cover full grown kale with hoops of row cover or clear plastic sheets (mini hoop tunnels). In times of extreme cold, an insulated, reflective cover over the frames at night is helpful as long as it’s opened during the day to let in the sun.

Take care to align the tops of angled ends (A) with the tops of the beveled front (E) and back (C) to create a flat plane for your storm-door frame. If you are sowing directly into a portable cold frame, have it in place two weeks prior to seeding to warm the soil for germination. Our goal at Walden Labs is to be the ultimate resource for building self-reliance and resilience, and learning about the survival skills of our ancestors.

Automatic temperature-sensing vents are inexpensive, but Visser vents his cold frame manually. However, their guide recommends a wooden cold frame that is three feet wide and four feet deep — using untreated lumber if you’re planning to grow food. In a sunken cold frame, the ground insulates and the sun gives warmth, but you still need to eliminate pockets of cold air that can harm overwintering plants.

By placing a small 1 x 4 shelf between the cleats, I can fit another row of plants into the cold frame, increasing its storage capacity without unduly shading the plants below. In most regions, a cold frame can be used effectively to grow winter seedlings and crops, though if you live in a climate zone below USDA zone 6, you may need a more fortified version than the one I use ( here’s a good example on Mother Earth News ).

The same technique was used to attach the rear of the cold frame to the side panels. Taken together, these steps will help keep temperatures in the cold frame from dropping too much. Arrange your straw bales in a rectangular shape no more than one-bale-wide to avoid cold pockets in the center of the structure. We built the cold frame in the fall and filled it with layers of old hay, horse and chicken manure, compost from our compost pile, and an assortment of egg shells, coffee grounds and fruit and vegetable peelings. Depending on how cold your weather gets you may want your straw bale joints to overlap more.

Seedlings started off indoors can be weaned off the warmer, protected conditions of the windowsill in a cold frame, too. Straw has been our material of choice, although people use lumber, bricks, and many other materials to create cold frames. This was a problem for me as all of my beds properly positioned for a cold frame still had other plants growing in them at this time. On the other hand, if a cold snap hits with freezing temperatures lingering, the plants may freeze. You can also grow a winter crop of vegetables in a cold frame (visit Niki or Brenda’s blog for inspiration).

We discovered that we also had to add an ‘inner lid’ of chicken wire to keep the family chicken flock from consuming the tender greens in the cold frame. Now that you have your cut pieces of lumber that you either cut yourself or had cut at your lumberyard, you are ready to assemble your cold frame. Thirdly, the sun is your only heat source so if you have a really cold snap, you may want to cover your cold frame with heavy blankets to keep you plants from freezing.

Of course, if you have added a heating cable that will help some, but probably not enough heat to save your vegetables, so covering during really cold weather is still a good idea. Whether you are starting seeds in flats or sowing them directly into the soil, a portable cold frame provides the opportunity to get your plants going a few weeks early, and it eliminates the transplanting shock that many plants face because they will be better acclimated from the outset.

For those of you who have harvested and eaten a salad of fresh greens in February or have flowers blooming well past frost, you know the attraction of using cold frames. To store my low tunnels, I simply roll up my fabric or clear plastic covers and store them in the attic for next year, and pull up the PVC conduit hoops, laying them flat and out of the way beside my storage building. In moderate climates, a cold frame can allow you to grow some herbs and vegetables year round!

One simple way to provide shade in otherwise exposed conditions is to build a portable shade frame for placing over rows after seeds are sown or transplants are set out. Now, for step by step instructions for building a cold frame from scratch, or using old windows, followed by a how-to video for building a complete cold frame on wheels, see page 2. The ideal size for a cold frame is 3 by at least 6 feet, about 12 inches deep along the front sloping to 18 inches at the back.

The chickens or the compost pile get the trimmings and the cold frame gets the compost made from the garden and animal waste. Cold frames have been used for centuries to start cold-tolerant plants in the early spring, harden off seedlings before transplanting, shelter tender perennials and even overwinter plants and cuttings. Shades protect winter you know where your cold frame will go, prepare the bed it will sit upon. There are dozens of kits available to help you build a cold frame, but it is actually pretty basic in design. Design Sponge created this off the ground cold frame from old windows and scrap wood.

Banking straw around the sides of a cold frame also keeps the heat in. The temperature inside a cold frame can rise rapidly necessitating the lifting of the glass top a bit to ventilate. When you use your cold frame, as well as where you position it and how long you use it, are all based on your growing zone, what you plant and your gardening goals.

Note that you’ll want to measure the height of your raised bed and adjust the cold frame leg measurements as needed. You can get your seedlings outdoors early in April because the cold frame creates a micro-climate protecting your small plants from the cold. Watering should be done early enough in the day so that foliage dries before nightfall or before the frames are tightly closed. If you’ll be using the cold frame on a deck or patio , consider setting it atop a couple of layers of the rigid foam board insulation.

Half-way down the short sides of the cold frame, attach a spare piece of wood to the inside top edge, flush with the sloping surface of the side. Opening the frame occasionally in autumn and winter will help prevent damp, stagnant air building up – the perfect breeding ground for fungal diseases. 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. Cold frames are great places to plant greens in late summer and hold them well past the first frosts of fall … and maybe longer.

Excess Heat: Those 5-10 degrees can also mean trouble when temperatures start heating up. Don’t forget to open the lid of your cold frame on warm days to keep the plants from baking. It is important to note that butterflies will be more tolerant of an enclosed environment when they are raised indoors from caterpillars. It helps to have the cold frame in place at least two weeks prior to transplanting to warm the soil. The cold frame, which stays a bit warmer, is great for potted seedlings that need some time hardening off after being started indoors. Well, now I have heard of and know what a cold frame is. Not something you just grow up knowing about in Texas, I guess.