Cold Frame Gardening 2: March

Jonathan moving cold frame
Jonathan moving cold frame

As the spring equinox draws near, the cold frame gardener finds it easy to stay busy. With greens, peas, and root crops already sprouted, it is a good time to look for holes in the rows of plants (often due to rodents) to re-sow. Be sure to keep the frames vented on sunny days and well watered. You can even remove the glazing entirely to catch any warm spring rains.

Now that your confidence in cold frames is swelling, you can begin to focus on your transplant seedlings. Assuming that you have already started your broccoli, lettuce, tomatoes, and other such delights, it is important to get these seedlings into containers in order to sustain the seedlings until transplant time. I tend to be short on space and will use small, 2 1/2″ pots with the option of re-potting into larger ones as needed. Though this is more work, I find it easier to keep a smaller area well protected and watered when the weather outdoors is still harsh.

Most seedlings need to be pricked out into pots about two weeks after germination, once true leaves have emerged and before the seedlings get too crowded and leggy. If (like me) you are without a greenhouse, your potted seedlings can get by with a cold frame that is well insulated with straw or leaves. A blanket and tarp also help reduce heat loss through the glazing on cold nights.

It is important to keep a watchful eye on the seedlings after they have been transplanted (bare rooted) into pots. Shading from direct sunlight is often necessary for the first few days. Lacking the buffer of a large soil mass, potted seedlings tend to be even more sensitive to extremes. Venting the cold frame is often necessary by mid-morning on sunny days in the 50’s. And all it takes is one frozen night to permanently shock a potted seedling’s root system.

Caring for seedlings in a cold frame in March is a delicate and demanding art. Guided only by a thermometer, observation, and intuition, the dedicated gardener must ensure that the seedlings survive and ultimately thrive through the extremes of temperamental Spring weather.

Why does the eager cold frame gardener bother to take on such a challenging task? Of course, there is the obvious explanation of early produce. What a shame to wait until July or even August for tomatoes when June and often May are already sunny and hot.

Another reason for all the labor that goes into extending the growing season is that it reduces the need for labor- intensive food preserving. Since the quality and nutritional value of fresh produce is incomparable, the cold frame gardener is doubly rewarded.

Moreover, cold frames reduce the temptation to purchase non-local produce whose real environmental cost is hidden. And any surplus from the cold frames can be bartered or sold to neighbors for a premium.

But there are other, less tangible benefits as well. I have found plants to be good reflections of our spiritual selves, with many parallels between caring for early seedlings and caring for one’s soul. Living in the somewhat protective environment of this community and this county, I often feel like a sheltered seedling. The warmth coaxes me to grow and evolve, but there is also the risk of being blasted by extreme conditions or negligent care. Like seedlings, we must trust in the coming season. When we are transplanted into the garden, and our roots are finally free to stretch deep into the Earth, our ripening fruit shall serve as signs of what is possible for the human species.

So by mid to late March you can begin to think about transplanting your hardier plants into cold frame protected garden soil where they ultimately belong. One of the main benefits of having individually potted seedlings is that there is virtually no transplant shock. Nevertheless, it is helpful to time the transplant during a period of mild weather and to warm the soil by moving the cold frames into place a few days prior to transplanting. You should hopefully be able to safely steal cold frames from the peas, root crops, and greens that you sowed last month.

Because my cold frames are precious real estate, I tend to pack them with plants that use extra compost and premium garden soil. When transplanting, I will crowd broccoli and cauliflower in staggered rows with 15″ spacing, even squeezing in some quick-growing lettuce in spare corners, to be harvested before their larger neighbors take over.

Less hardier crops like tomatoes, peppers, and basil will need to remain potted a month longer, until the cold frame housing your broccoli and lettuce frees up in April. The tomatoes especially may need quart-size pots before long to tide them over until then. More on the care of these warm weather crops and the maturing plants in your cold frames next month.