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Planting and Seeding Seasons

GENERAL CONSIDERATIONS. Comparative data based on the best reliable sources of information relative to planting seasons and lawnseeding seasons are so interesting and so valuable, as a basis of establishing definite relationships among varying sections of the United States, that the writer has been prompted to attempt a diagrammatic and a tabulated analysis of this important question (See Plate III). Considered from the standpoint of a plant the act of transplanting is a violent one and consists of stopping at once a large part of its vital activities, generally causing the loss of a considerable part of its root system. Therefore, transplanting should be accompanied by precautions to prevent too great loss of moisture by transpiration, and by measures to assist the plant in starting growth at the earliest possible date. Seeding differs from transplanting in that a seed is a ripened embryo which is a minute but complete dormant plant. As the process of germination includes the making of a vital connection between the young plant and the soil sufficient to enable the plant to produce green tissue and support itself, seedage must also be surrounded by precautions to insure proper conditions for germination. One of the most important factors in transplanting or seeding is the selection of the correct season, because upon the successful start of the operation depends the whole future of the plant. Plants grown in pots, or so root pruned that nearly all their roots may be moved with them, are, of course, in condition to be moved at all sorts of odd seasons, but this latter is the work of experts or trained gardeners and is not to be recommended to amateurs on account of the technical knowledge and skill required both during the planting operation and in the way of proper after-care and maintenance. This discussion is confined to transplanting dormant plants and to seeding of lawns, under the following headings: (a) Deciduous Trees, Shrubs, and Vines (b) Evergreen Plants Coniferous and Broad-leaved) (c) Herbaceous Perennials (d) Lawn Grasses Greenhouse plants and the propagation of plants by seeding, except as referring to lawn grasses, are not included because conditions vary so widely in the same locality. DECIDUOUS TREES, SHRUBS, AND VINES. The transplanting of deciduous trees, shrubs, and vines is commonly carried out during their dormant season. It is possible in the spring, however, to carry on planting of deciduous woody plants, at a time when the local plants are too far advanced to be moved, by the simple expedient of bringing plants from a storage cellar or from a more northerly nursery where they are still dormant. Again in the autumn, these same northerly grown plants may be used to start planting work before the local plants are matured and safe to move. Transplanting seasons are not so much governed by north and south latitude as they are by the condition of the plants, as explained in another paragraph under discussion of life-zones.

The beginning of the dormant period for woody deciduous plants comes in the autumn when their wood is matured and ripened and the leaves start to fall or to take on their autumn colouration. This occurs early in such plants as lilacs, lindens, flowering currants, and horsechestnuts, and it will usually be found to occur late in some of the plants which are said to be hard to move in the autumn, such as poplars and silver maples. From the beginning of the dormant period in the fall until the beginning of physiological activity in the spring, deciduous plants may be moved at any time that the ground is in proper condition and the temperature favourable. As a matter of practice, in the northern states this work is suspended entirely during a normal winter, for about four months, except where large plants are moved with a frozen ball of earth about their roots, because frozen ground and snow make the operation of transplanting smaller plants entirely impracticable. This period, longest in Maine and in the section surrounding Minneapolis, lessens as one goes farther south, until in Virginia and Georgia a continuous planting season extends without interruption through the dormant period.

It was early learned that the whole of North America could be conveniently divided into seven transcontinental belts or life-zones, based upon the length of the growing season, which has been defined IO as the period between the date in the spring when the normal mean daily temperature rises to 43 degrees Fahr., or above, and the date in the autumn when it falls to below that figure. (The reader should consult Bulletin No. 10 of the U. S. Department of Agriculture, Division of Biological Survey, entitled "Life Zones and Crop Zones." Part III of that Bulletin is especially interesting). These life-zones are, as noted above, adapted to plants requiring growing seasons of similar length and temperature range. Thus, if soil conditions, exposure, and amount of annual rainfall are alike in two distant portions of a zone plants which succeed in one portion may be expected to succeed in the other portion. They may in any event be tried out with considerable confidence when all the conditions are known to be the same, as described above.

It now seems evident, from recently gathered data, that these zones correspond very closely to belts of country which have similar planting seasons for dormant woody plants, at least throughout the humid regions east of the 100th parallel of latitude. By consulting the accompanying Plate II, which has been adapted from the one in the above-mentioned Bulletin, and also the chart (Plate III), which shows the reported length of planting seasons, it will be seen that the stations reporting fall into groups which lie in respective life-zones as shown on the map.