had been buried under ice and snow for more than three months
and I didn’t expect many survivors. Sometimes, close to 3
feet of snow interspersed with the solid strata of ice that
accumulated above them. Temperatures had spent a good deal
of time in the zero-and-below range. Despite the hard winter,
when I opened the cold frame in my backyard there was a cheery
green of life. There were a few casualties, but most of the
plants I’d placed in the device last fall were sending out
new tender leaves and ready to grow with spring’s strengthening
light. I saw future homegrown salads in the forecast.
A cold frame is like a miniature passive-solar greenhouse.
Its basic design is a frame with a transparent cover over
it that allows light to enter. The back side of the frame
is often higher than the front. The top slopes down toward
the front, allowing more light in and facilitating the runoff
of rain and melted snow.
Cold frames are generally dug into the earth, such that the
soil level inside becomes lower than the level outside. Compost
and other fertility enhancements are often added to enrich
the soil inside cold frames, which have no bottom and remain
open to the earth below. These semisubterranean structures
insulate plants from frosty temperatures, buffeting winds,
and frozen precipitants. The warmth of the soil and the heat
of the sun help moderate cold-frame temperatures. These “solar
boxes” can add productive weeks to the growing season.
The cold frame’s simplest, recycled-junk version is an old
wooden storm window with its glass intact, sitting atop a
frame of wood that has earth mounded up on all sides. I’ve
learned from trying such a design that this technological
minimalism can work amazingly well in adding to the veggie-growing
days of the year.
I started experimenting with cold frames more than 20 years
ago. I built my first one out of junk wood and made its transparent
cover out of plastic sheeting stretched across and stapled
to a wooden frame. Its dimensions were about 2 feet by 3 feet,
with a back wall that was about twice the height of the front.
I oriented it to face south, making the most of the low arc
of the winter sun. Along the cold frame’s back wall I stacked
plastic jugs of water painted black as a simple means to store
some of the sun’s heat. As the fall earth cooled, I planted
some lettuce seedlings inside and hoped for the best.
I found that the plants in the cold frame grew for a short
period in the late fall and then went dormant. They remained
green, but produced no new leaves during the short days and
cold of winter. It seemed that the low light levels didn’t
provide enough energy for growth. However, when the days lengthened
as the calendar proceeded toward spring, the plants started
growing again, and by the end of March a few small, tasty
heads of lettuce began to form. The lettuce that wintered
in my cold frame had grown better than it had in the previous
spring’s garden. I was soon sold on cold frames.
Last August I started a number of cold-hardy leafy vegetables
from seed, attempting to squeeze out a late fall harvest from
my backyard garden. As October approached Halloween, I began
to dig these plants out of the garden and transplant them
into my current cold frame (a commercially available type
constructed of quarter-inch double-walled plastic that I’ve
used for 15 years). The plants had at least a month to adapt
to their new environment before the cold and frozen precipitation
began to set in. Among the veggies I transplanted into my
cold frame were: Green Deer Tounge, Red Rollo and Green Salad
Bowl lettuce varieties; tatsoi (a compact Asian mustard);
mâche (also known as corn salad); cress and Red Russian kale.
Together these added up to a healthy, winter-hardy salad.
As the plants in the garden gave up their green to the frosty
forces of fall, the cold-frame dwellers lived on.
Last Thanksgiving, I picked a small but much-appreciated salad
from the cold frame. It was my last backyard salad of the
year. Mixed with sprouts of alfalfa, broccoli, radish, mustard,
mung bean, kale and fenugreek that I grew on the kitchen counter,
it was a particularly nutritious (and totally homegrown) ending
to the growing season. Soon temperatures dropped and the snow
began to pile up. My cold frame disappeared for weeks at a
time beneath drifts of white, which actually provided further
insulation while letting light filter down to the tender greens
below. As the light of day lengthened and the calendar moved
toward spring, the plants began to actively convert sunshine
On the 23rd of March I picked my first salad of 2003. It included
both the variety of greens and sprouts mentioned above, as
well as the first tender pickings of some additional varieties
of leafy vegetables I had started in pots in late February
on shelves in the windows of my house. At the start of April,
I transplanted some of these indoor plants to the cold frame,
filling in available space. I will soon transplant these cold-frame
veggies into the garden, freeing the space up for another
important garden function.
I start a number of vegetables indoors, including tomatoes
and chili peppers. These need to be eased into the outdoor
environment in order to avoid severe and possibly mortal injury.
My cold frame also functions as a short-term stop between
the indoors and the outdoors where such plants can be more
gradually “hardened off” to the temperatures, sunlight, wind
and other conditions of the outside world. Meanwhile, I continue
to pick leaves from my cold-frame veggies for some mighty-fine
Thanks to my cold frame, I was able to celebrate Earth Day
with a fresh salad of rich greens. Somehow, it seemed ever