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Coming out of dormancy in the spring, a tree puts most of its energy into growth through all its upper parts. As summer wanes, energy is transferred to extending and strengthening the roots and to storing up a reserve to start new growth in the spring. Hence autumn feeding and spring feeding have different effects. On the whole, and especially for trees whose size is satisfactory, autumn feeding is best, from the September rains until hard frost. For trees whose size it is desired to force, or whose vigor was low last growing season, spring feeding is preferable, from mid-March to mid-June in temperate America. In the deep South and arid West, variations will be dictated by expectancies of heat and rainfall. Old trees are sometimes likened to freight trains for the momentum of their growth or decline. When a thriving old tree suffers hardship in its roots, such as disturbance by bulldozing, or successive years of drought, or a severe and snow less winter, the effects may not show up for some time, and then only gradually. The tree's stored up energy, like a freight's ponderous headway, keeps it "coasting." Signs of decline to watch for, apart from obvious die-back and deadwood aloft, are decreases in the length of annual twig growth, and in the size and greenness of the leaves. But after the occurrence of a hardship, it is better not to wait for trouble signs. Feed the tree and fend them off. Bulldozing has been mentioned as a threat to tree roots. Not only the blade and crushing treads are to be feared. The machine's mere weight can so impact the soil that it becomes impervious to air and moisture. And in grading, any overlay of soil more than three or four inches deep is likely to suffocate the sturdiest root systems. |
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