CHAPTER VI.[ToC]
THE SITE FOR AN ORCHARD.
A MATTER OF IMPORTANCE, NOT OF MERE CONVENIENCE—LOW VALLEYS LEAST DESIRABLE—BASINS, EVEN IF ELEVATED, SUBJECT TO FROSTS—LOCAL DIFFERENCES OF TEMPERATURE, OFTEN FATAL TO TENDER VEGETATION—THE FROST LINE NOT DEPENDENT UPON MERE ELEVATION, BUT UPON RELATIVE ALTITUDE—MODERATE BLUFFS BESIDE VALLEYS, OR RIDGES IN A PRAIRIE, ARE BETTER THAN HIGH VALLEYS AMONG MOUNTAINS—DRIFT FORMATIONS, PRESENT INEQUALITIES OF SURFACE—FAVORABLE INFLUENCE OF THE WATER OF RIVERS AND LAKES UPON THE CLIMATE—INSULAR POSITIONS AND LACUSTRINE SITUATIONS HAVE A PECULIAR CLIMATE—FOGS—LATENT HEAT BECOMING SENSIBLE—METEOROLOGY WILL FURNISH AID TO THE ORCHARDIST—COLD STORMSAspect—PROTECTION FROM WINDS, ESPECIALLY A PRAIRIE QUESTION—EFFECTS OF AGITATION IN THE ATMOSPHERE—BELTS AND SCREENS OF TIMBER DESIRABLE—WINTER KILLING OFTEN DEPENDENT UPON THE CONDITIONS OF THE TREE—VARIETIES MOST SUBJECT TO THIS—LISTS—SOILS, PERMEABLE AND TENACIOUS—ADAPTATION OF SORTS TO SOILS—GEOLOGICAL FORMATIONS TO BE OBSERVED IN MAKING SELECTIONS.
Site.—The selection of a suitable site for an orchard is a matter of no small moment to him who would be a successful grower of fine fruits. Without, at this time, pausing to inquire into the characters of the soil, let us examine more particularly the aspect of the field to be appropriated to this important crop; for the orchard is a permanent investment, and so much depends upon the site, that we should make some sacrifice of our convenience, rather than commit any error in this particular. In the first place, then, let it be understood that the orchard should be well exposed to the sun and air. The least desirable positions for orchard planting are narrow valleys, particularly limestone valleys in a mountainous country, traversed by a small brook, or where the surface is spouty from springs or subjacent water. Even if such depressions are considerably elevated, but surrounded by higher and abrupt elevations, they will be found obnoxious to late and early frosts in spring and fall, especially the former, which are often disastrous in such situations, after the fruit-buds have expanded in these sheltered nooks. Every one at all conversant with meteorological observations made in a broken country, is aware of the different range of temperature that will be indicated by instruments suspended at different elevations.[19] When the cooling influence of radiation has lowered the temperature of the surface of the earth and of objects near it, the stratum of air in immediate contact will be chilled, and growing heavier, will flow down into the most depressed situations, and, accumulating there, will cause a difference of several degrees of temperature. This, when near the freezing point, will be of the greatest consequence to tender vegetation, which may be preserved in perfect safety at forty degrees, but will be destroyed at thirty degrees, or even at a higher point, in some cases.
The frost line becomes a very important subject of inquiry in the selection of an orchard site, and in some countries we find that its position may be definitely settled within a limited range of elevation; not that a certain level can be indicated, above which there will always be an immunity from frost, while all below will suffer, but we may approximate, in certain situations, so nearly as to indicate that certain sites are safe or unsafe.
Nor is it the absolute elevation alone that is to be taken into the account; in any given locality, we may assume that the higher the orchard is situated above the water levels, the safer it will be, and that the lowest depressions are the most unsafe or frosty. It is not always the mere elevation, but rather the relative elevation of the site, that renders it more desirable than another in the same region. There are many orchards that are situated upon a moderate bluff, with a rapid descent of only a few feet or yards, into a swale or valley of moderate extent; these we find to be uninjured, when another at a greater elevation, but in a depressed basin surrounded by higher lands, will be found to have suffered from the influence of frost. In the one case, the cold air could flow off rapidly into the adjoining depression, while in the other, the cold air from adjoining slopes would collect, and accumulate in the situations described.
In the great plateaus of the world, we often find immense tracts of land so nearly of the same level as scarcely to afford sufficient drainage for the surplus water; of course, we should expect to find, in such places, little variation of temperature arising from difference in elevation. But even in such situations, whether we examine the table-lands of our timbered regions, or the extended areas of the prairie country, we shall find that the drift formation which covers these vast tracts, has not been distributed evenly, but that there are successive rolls or swells frequently recurring, which give, in some instances, considerable variations of level. A bold ridge, of fifty feet or more in hight, rises abruptly from the level prairie, stretching along for miles, and affording admirable exposures for orchard sites. Such places are observed to be free from late and early frosts. In other places, there is an abrupt depression of the surface, answering the same purpose—drawing off the cold air. These may be very moderate in their extent, as the prairie sloughs, or they may be small vales, the courses of the minor streams, or of larger extent, the valleys of rivers, or the depressions of lakes. In these latter cases, the modifying influences of considerable bodies of water enter into the frost problem as an element of no mean value.