OUR SUN-HEATED GREENHOUSE

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WINTERTIME LETTUCE

We come now to lettuce, which is very important to us because we use it so frequently in salad making, and go out of our way to have this tender fresh green for at least one meal every day.

Lettuce is a rather fussy cold weather plant. During a zero night the entire lettuce plant is frozen stiff. When the sun thaws out the plants, those with thin leaf stems continue green and alive and go on living normally. After several freezings, lettuce with thick leaf stems begins to rot. The leaf stems in Oak Leaf lettuce, for example, are relatively thin. The stems of Simpson lettuce also are thin; the leaf stems of Romaine are juicy. The Butterhead lettuces generally have moderately thick leaf stems.

As our experiments have proceeded we have found that Simpson, Oak Leaf, Green Boston, Buttercrunch, and other lettuces with particularly dry leaf spines have survived during our Maine winters. With one exception (the winter of 1975—76) we have succeeded in carrying some—at least—of our lettuce plants through every winter. Almost always they went into winter as half-grown plants or even as plants still in garden flats.

Our lettuce plants still in shallow garden flats were wiped out the winter of 1976-77, while those in beds survived. Weathermen counted ten distinct storm cycles from the middle of November 1976 to the end of February 1977. These storms followed one another closely, without a single thaw break. In the severest weather the curly endive and escarole were retarded but did not die. Their growth was checked but they were not killed by weeks and months of sub-zero frost.

ESCAROLE, A SURVIVOR

We would like to refer especially to a bed of broad-leafed Batavian escarole which we raised in a seed flat and then transferred to a garden flat. They were three inches high when moved into a greenhouse bed and covered with autumn leaves. All of these plants survived the same winter that killed the lettuce which was in flats.

As we pass this unusually persistent and prolonged winter season in review, we are pleased we went through it before we wrote this book. Despite its extreme severity we can report that we were able to carry a variety of vegetable greens through one sub-zero period after another with no thaw in between. Each sub-zero cycle proved to us that our basic assumption concerning the capacity of succulent green vegetation to outlast deep freeze is established beyond question.

OUR FRAGILE CELERY

At the other end of the equation is the recognition of the unquestioned fact that all growing things have their limits. Celery is more fragile than lettuce. Its leaf stems are thick and juicy. In the winter of 1976—77 we had a bed of celery plants which we had raised from seed, put into garden flats, and heeled into the greenhouse in the autumn of 1976. The celery plants took the transplanting well and went into the winter lightly mulched. We then entered into the toughest winter in memory. In the course of that winter this batch of celery was completely wiped out, but it survived for more than a month with outside temperatures down to seven degrees below zero ... and up to that time showed little frost damage.

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