This section is from the book "The Gardener's Monthly And Horticulturist V21", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
This term in common practice is only made use of in those cases, where the temperature of the soil in which the plants grow, is artificially raised above that which we find naturally in it, and there seems to prevail a general idea, that such an artificial elevation of temperature is only necessary in a few special instances. How erroneous this idea however is, may be seen in the fact that the mean temperature of that part of the soil in which plants grow, is universally somewhat higher than the air surrounding them. It is however not the special degree of bottom heat, which plants require so much at certain periods, but a correct and corresponding proportion of the temperature of the soil, to that of the atmosphere and the intensity of light. It is therefore to be presumed, that we might and perhaps ought, to give more heat to the roots of plants, we cultivate here in America, than is necessary to the same in Europe, as we have more light and sunshine, than they have there. Both forcing, and the cultivation of tropical plants and fruit are therefore greatly facilitated, and it is the more to be wondered at, that our people, even the rich, buy and eat that poor stuff sold in our markets, as pineapples, bananas, guavasr etc, and that forced strawberries are yet too expensive for both producer and consumer, since we have not learned to grow them except in pots, and therefore figure on some tables as a mere show.
Graperies and fruit houses might be got up cheaper and be managed at less expense then they are, and made to produce better peaches, apricots, plums, and above all cherries, out of their season, of a quality and at prices, both unknown even to the wealthy in this country.
We still read in the, perhaps too numerous and expensive books on horticultural and agricultural subjects a good deal of nonsense regarding the soil, which this or that plant is said to prefer or actually demand for its well-being; whilst for more than forty years ago it has been proved, that it is not the chemical or min-eralogical composition, but the combination of moisture and temperature of the soil which constitutes the principal condition of vegetation. It may be considered an axiom in horticulture, that all plants require the soil as well as the atmosphere in which they grow, to correspond in temperature with that of the country of which they are natives. It is for the want of sufficient bottom heat, that some grape vines do not set their fruit well; that tropical palms and other plants, where it is impracticable to heat the soil in which they grow, soon become unhealthy and that some get covered with a black mould, as orange trees, myrtles, eupatorium, veronicas and many others, which we meet with in our so-called conservatories, but which are not cultivated in them, living barely through the Winter until planted out, when our Summer, with the heated soil comes to their relief.
To what extent the soil to the depth of about one foot is heated, in the different parts of the world we can only form an unsatisfactory idea, since so few actual measurements have been made, and as yet none at all have been made in the United States; though we have an agricultural department in our government, with a full complement of well-paid employes.
We know, however, that seeds of tropical plants will not germinate even, unless the soil is permanently heated to at least 75° F. That whilst in Nova Zembla the soil was not warmed above 34 1/2° F. with Ranunculus nivalis and Oxy-ria reniformis in bloom, and in Takutzsk, wheat, rye, cabbage, turnips, radishes and potatoes were cultivated, though the soil never thawed to more than about three feet, and in the garden of the Royal Horticultural Society, London, the heat of the soil varied between 37° and 66° during a twelvemonth, Sir John Hershel in a bulb garden, at the Cape of Good Hope, observed it to be 159°. In Egypt it is from 133° to 144°, and according to Humboldt, in the tropics from 126° to 134°, in some places 140°. In Chili 113° to 118°. Bermuda 142o. And in France 118° to 122° even as high as 127°. The Orange tree is only found in perfection where the heat in the soil rises to 85° and never falls below 58°.
The real difficulty with regard to bottom heat has been, not so much the necessity of it, but the manner of obtaining and applying it. Tanks have proved too damp, pipes too dry, dung and bark constantly subject to excess and defect. But as long as we cultivate our plants in pots only, which are surrounded by a sufficiently high temperature of the atmosphere, one will have little difficulty in supplying the necessary heat to the roots; but as long as our present means and mode of heating do not give to the plants the necessary, and, according to circumstances, carefully to be regulated bottom heat, together with the requisite moisture, our in-door gardening will remain an undeveloped and unsatisfactory proceeding. It is therefore not to be wondered at that so little interest is shown in it by our wealthy people. Let gardeners, rather than learn how to grow orchids or to milk a cow, learn to understand and apply the principles and explanations of science, to the routine of horticultural practice, and it cannot fail that the intelligent will take a more lively and active interest in that beautiful art, which seems now to have dwindled down to the mere production of a few kinds of flowers, about as easily produced as weeds.
[We commend strongly the main point of Mr. Poppey's communication, which is that too few gardeners take an intelligent interest in their profession. We know the general answer to be that there is little inducement; that gardeners are too poorly paid, and therefore they abandon the field to mere laborers who seem to monopolize the term "gardener." It is true that many worthy men do not find the place for which they are eminently fitted, and that miserable fellows occupy positions better men should fill; but this is no more true of horticulture than of many, nay of all other professions. It does not hurt any gardener to know someihing of the more intelligent subjects connected with his profession. There is a pleasure in knowledge for its own sake, independently of any money that may accrue from it possession; and the intelligent gardener has at least an equal chance in the race for good positions as the dolt. There are continually places; well paid places, open for intelligent persons; and though the wrong person often gets into the right place, we know that it is not always so. - Ed. G. M].