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The following classification will show the value of the more important trees for different kinds of planting. The species are arranged in the order of their merit for the particular object under consideration and the comments accompanying each tree are intended to bring out its special qualifications for that purpose.
Conditions for tree growth in one part of the country differ from those of another and these lists, especially applicable to the Eastern States, may not at all fit some other locality.
Quality of trees: Trees grown in a nursery are preferable for transplanting to trees grown in the forest. Nursery-grown trees possess a well-developed root system with numerous fibrous rootlets, a straight stem, a symmetrical crown, and a well-defined leader. Trees grown in neighboring nurseries are preferable to those grown at great distances, because they will be better adapted to local climatic and soil conditions. The short distances over which they must be transported also will entail less danger to the roots through drying. For lawn planting, the branches should reach low to the ground, while for street purposes the branches should start at about seven feet from the ground. For street planting, it is also important that the stem should be perfectly straight and about two inches in diameter. For woodland planting, the form of the tree is of minor consideration, though it is well to have the leader well defined here as well as in the other cases. See Fig. 95.
When and how to procure the trees: The trees should be selected in the nursery personally. Some persons prefer to seal the more valuable specimens with leaden seals. Fall is the best time to make the selection, because at that time one can have a wider choice of material. Selecting thus early will also prevent delay in delivery at the time when it is desired to plant.
When to plant: The best time to plant trees is early spring, just before growth begins, and after the frost is out of the ground. From the latter part of March to the early part of May is generally the planting period in the Eastern States.
Where one has to plant both coniferous and deciduous trees, it is best to get the deciduous in first, and then the conifers.
How to plant: The location of the trees with relation to each other should be carefully considered. On the lawn, they should be separated far enough to allow for the full spread of the tree. On streets, trees should be planted thirty to thirty-five feet apart and in case of the elm, forty to fifty feet. In woodlands, it is well to plant as close as six feet apart where small seedlings are used and about twelve feet apart in the case of trees an inch or more in diameter. An abundance of good soil (one to two cubic yards) is essential with each tree where the specimens used are an inch or two in diameter. A rich mellow loam, such as one finds on the surface of a well-tilled farm, is the ideal soil. Manure should never be placed in direct contact with the roots or stem of the tree.
Protection of the roots from drying is the chief precaution to be observed during the planting process, and for this reason a cloudy day is preferable to a sunny day for planting. In case of evergreens, the least exposure of the roots is liable to result disastrously, even more so than in case of deciduous trees. This is why evergreens are lifted from the nursery with a ball of soil around the roots. All bruised roots should be cut off before the tree is planted, and the crown of the tree of the deciduous species should be slightly trimmed in order to equalize the loss of roots by a corresponding decrease in leaf surface.
The tree should be set into the tree hole at the same depth that it stood in the nursery. Its roots, where there is no ball of soil around them, should be carefully spread out and good soil should be worked in carefully with the fingers among the fine rootlets. Every root fibre is thus brought into close contact with the soil. More good soil should be added (in layers) and firmly packed about the roots. The last layer should remain loose so that it may act as a mulch or as an absorbent of moisture. The tree should then be thoroughly watered.
After care: During the first season the tree should be watered and the soil around its base slightly loosened at least once a week, especially on hot summer days. Where trees are planted on streets, near the curb, they should also be fastened to stakes and protected with a wire guard six feet high. See Fig. 95. Wire netting of ½-inch mesh and 17 gauge is the most desirable material.
Suggestions for a home or school nursery: Schools, farms, and private estates may conveniently start a tree nursery on the premises and raise their own trees. Two-year seedling trees or four-year transplants are best suited for this purpose. These may be obtained from several reliable nurseries in various parts of the country that make a specialty of raising small trees for such purposes. The cost of such trees should be from three to fifteen dollars per thousand.
The little trees, which range from one to two feet in height, will be shipped in bundles. Immediately upon arrival, the bundles should be untied and the trees immersed in a pail containing water mixed with soil. The bundles should then be placed in the ground temporarily, until they can be set out in their proper places. In this process, the individual bundles should be slanted with their tops toward the south, and the spot chosen should be cool and shady. At no time should the roots of these plants be exposed, even for a moment, to sun and wind, and they should always be kept moist. The little trees may remain in this trench for two weeks without injury. They should then be planted out in rows, each row one foot apart for conifers and two feet for broadleaf trees. The individual trees should be set ten inches apart in the row. Careful weeding and watering is the necessary attention later on.