This section is from the book "The Gardener's Monthly And Horticulturist V22", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
E. F. H., West Plains, Mo., writes: "In the March number of the Monthly, pp. 87, in answer to ' Inquirer,' Burlington Kansas, you say: ' So far as known, the buds of plants burst into leaf solely from the action of heat on the buds, and the temperature of the earth has nothing whatever to do with the act of foliation. Is this so, with regard to the flowering of our fruit trees? Will not root action, by feeding the bud cause the bud to grow and burst into flower independent of the temperature of the atmosphere, if the earth is sufficiently warm. If not, why mulch our trees to keep from early bloom. I have peach trees mulched and unmulched standing side by side: the unmulched are now (March 8,) in bloom, while the mulched show little indications of bloom for many days yet".
[We are glad to get letters like this. Such letters show an investigating spirit, which it would profit intelligent horticulture did it prevail more extensively. No practical gardener would doubt the proposition as presented to "Inquirer," nor do we suppose any teacher of vegetable physiology would question it. For those who have not been in either school it may be useful among many similar observations that might be quoted, to say that it is no unusual thing for gardeners in forcing grape vines, to have a branch of a grape vine run out from a house that is being forced, to one that is cold - that is from a forcing grapery to a cold grapery. The branch in the cold house will remain wholly dormant, while the one in the heat is in leaf and flower, and advancing on towards a fruiting state. Again cases are by no means uncommon where grape houses have the roots out of doors and the branches inside. The temperature of the earth may not be much above the freezing point, but the vines go on to leaf, and fruit just as well when the proper heat is applied to the branches as when the ground containing the roots is exposed to summer heat.
Indeed the writer of this once knew of an outside grape border, which was very narrow, perhaps not four feet wide, and about two or three feet above the surrounding level. The grape stems were drawn through a hole in a sixteen-inch stone wall to the house inside. There is every reason to believe that in that severe winter the ground in that border was frozen two or three feet thick, - but the grape vine pushed into leaf and flower on the application of heat with the most perfect indifference to the frozen roots, so far as any human eye could see. This is among the numerous evidences that the practical gardener might adduce.
The physiologist also has his separate field of reasoning. He sees a willow log, or for that matter many other kinds of log, cut off, lying on the bare ground, without any roots, and yet push buds into leaf, and grow when the warm weather comes, without any roots at all!
Then there are many facts which might be drawn from meteorological observations, which prove the same. For instance the past winter in Pennsylvania. There it has been one of the mildest winters, in a certain sense, on record. The earth has not been frozen much over an inch deep all winter; while as a general thing it is frozen from one to two feet the whole winter. Tree roots, instead of being for four months subjected to a temperature below the freezing point, have probably been favored with a temperature of 40° or 45°. Yet usually the willow trees before our window, as we write are quite green by the 21st of March, but on the 20th of the month are quite brown, - and no other trees have buds forwarder than they usually have, and the reason is that though the winter atmospheric temperature has not been low, neither has it been high. We have had scarcely any warm days. Indeed the atmosphere all winter has been decidedly cool if not frosty. In snort it is the atmosphere and not the soil that causes the development of the leaf.
Now as all this must be true, we come to our correspondent's special case. There is no doubt of his facts, for it is a matter of common observation, that an orchard in grass does not bloom so early by a few days as one on cleared ground. But we never heard before that it was because the " ground was warmer," but because the air was cooler. Just as we find a nice grassy field a much pleasauter place to walk over on a hot day than on a dry grassless road. The grass keeps the atmosphere cool as well as the earth.
It is quite likely if our correspondent would place a thermometer six inches or a foot under ground where the bulk of the roots are, in the mulched and the unmulched cases, he would find the thermometer much the same in both instances, - on the other hand if he place a thermometer on the trunks of trees "in grass" and trees in "cultivated" ground, and keep the record by a registering thermometer, he will find the atmospheric heat favor the clear ground trees.
The mere scientific or old-fashioned practical man may think we occupy too much space in " telling nothing new," but the inquiry of our correspondent, as well as of "Inquirer" in the first instance, shows that some of these things have to be gone over again and again, - and in this case, besides the strict scientific value of the question it is one of great practical importance. Ed. G. M].