The tree-seedling permitted to stand where the seed was planted extends the main or water-feeding roots downward, if the soil is favorable, to a depth of several feet. The writer has traced the tap-root of a Buckeye seedling one foot in height to a depth of five feet. In the deep gullies or washes in the loess soils of western Iowa we have seen roots of older trees that were two inches in diameter at a depth below the tree-crown of twenty feet. But the depth reached depends on the nature of the subsoil and the depth of the water-level. The branch or surface-feeding roots also reach farther than is usually suspected. As a rule, if conditions permit, the surface nitrogen-feeding roots extend beyond the spread of branches. The deep extension of the seedling-root that goes down where the seed is planted, and the speedy extension of surface-feeding roots, has led planters of groves and plantations of forest-trees in Europe and America to plant seeds where the trees are to stand.
In practice it has been found that seedlings not transplanted are much larger and thriftier when ten years old than the two- or three-year-old plants set out when the seeds were planted. If practicable, the budding and grafting of seedlings standing where the seed is planted would prove a great advantage. But in this case the roots that favor rapid and thrifty growth of the top are not as favorable for transplanting as those that have been transplanted.