This section is from the book "The Gardener's Monthly And Horticulturist V23", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
I have tried dipping in cold water and sprinkling, and generally with unfavorable results - perhaps from not managing it right - from the fact that plants out of doors will pass through a pretty severe frost unharmed when clouds or fog obscure the sun's rays in the morning. I have taken a hint, and several times have saved frozen plants in my greenhouse by building a fire of half-rotten wood, damp brush, etc, in an open vessel, so as to fill the house with smoke and steam. I think it is the generally received opinion that, like the Irishman who "was not hurt by falling, but by stopping so quick," it is not so much the freezing as the sudden thawing which destroys them. But I am inclined to think there may be some peculiar action of the sun's rays (perhaps the chemical rays), which does the mischief. I have observed that the very first rays that strike a frosted plant seem to kill it at once, while in some experiments in thawing by smoke and steam some plants have been thawed quite rapidly by the fire, and came out all right.
This is also further confirmed by a somewhat novel method adopted by a lady near here during the late cold turn. The earth in a pot of Smilax was frozen quite hard at the top, and a calla was frozen so that the leaves were bent down, and as soon as she could heat a little water in the tea-kettle, it was applied to the soil around the plants in a boiling state, and the calla leaves straightened up, while the water was being poured on, and both plants came out comparatively uninjured.
And just here comes in appropriately a word about the "freezing of trees and plants in winter." I do not feel quite satisfied to accept the editor's theory that trees cannot freeze solid without being destroyed thereby. I would like to have him test this in a New England forest on a cold winter day by trying an axe on some of the trees, and also note the explosions often produced by the cracking of limbs in a sudden freeze - like that produced by ice in a sudden and severe freeze after a thaw. One of our citizens, who has been in the "Christmas tree" business for several years, says that the weather was so cold in Maine in the early part of December, 1880, that the balsam fir trees could not be handled without breaking in pieces, and he was obliged to give up the job. This sounds to me very much like freezing solid. Is it not just possible that trees are so protected by their bark from the direct action of the sun's rays that the frost comes out as it does from plants in leaf during a fog, as in cloudy weather?
Last December, I found one morning one of my houses with mixed plants, mostly geraniums, some Smilax and heliotropes, frozen, so that the ground was hard in many pots; and as we had watered late in the evening, the water froze on the leaves in some plants over an eighth of an inch. We started the fire slowly, raising no higher than 45° that day, watching all the time to see the leaves wilt and droop, but they kept their place, and do so yet; they only have a brownish cast. I had frozen plants before, and lost them; and marveled about what could have produced this better result, until I read the article in the Gardener's Monthly, from W. F. Bassett, to keep off the sunlight. We had no sunlight at that time for three days, and I conclude that this was one of the agents that saved my plants.
It is an old popular idea that shading plants after being frozen tends to lessen the injury. I have great doubts of its correctness. Some twenty years ago when houses were built on what is called the ascending plan, whereby they could be more uniformly heated by flues throughout, I had some nine or ten houses so constructed that were so elevated about five feet in one hundred. This elevation was a little too much, for it was found that the heat was greater at the high end than at the end where the furnace was placed. Sometime during the winter the thermometer fell to 10° below zero, with the wind blowing a hurricane which blew down the chimneys and in a great measure destroyed the heating power of the flues, and as a consequence the contents of nearly every house we had was frozen, but that portion which was lowest, although the furnace end, was most severely. The frost tapering in degree as the houses ascended, so that the plants at the high end were hardly injured at all. My foreman was a great believer in the shading theory, while I was not, but believing it would do no harm I agreed that one-half of the houses should be shaded by shutters while the other was left exposed to the full sunshine. The results were the same, as near as could be, in both cases.
Where the plants had been severely frozen they were killed outright, lessening in a degree as it reached the high end of the houses. How far plants will stand frost in a greenhouse of course much depends on what they are and the degree of temperature at which they have been grown; but this marked example which I have related, and others of similar character which have come in the course of my experience have convinced me that just in the ratio of the degree of frost, coupled of course with the condition of the plant, will be the injury done, no matter what means are taken to remedy the evil. Scarlet fever or diphtheria strikes the household. The doctor comes and prescribes - some recover - some die, though the treatment has been the same. The same results follow when no doctor has been called - some recover - some die. The reason is obvious, as in the matter of frozen plants, the disease has been more intense in some cases than the others, or the patient has had more strength of constitution to bear it.