The cultivated orchard fruits vary peculiarly in the manner of root-growth when grown on their own roots or grafted. With a given lot of apple-seedlings, if we graft enough for a nursery row of Soulard Crab and for another row of Ben Davis, we find on digging when two years old that the Soulard roots run down and are as difficult to dig as pear-trees. But the Ben Davis row we find easy to dig, as it has a great supply of fibrous surface-roots, and the deep extending ones are small but numerous. Indeed, with the same seedlings we find that the roots of all the varieties will maintain their usual characteristics of growth when on own roots.
Every nurseryman is familiar with the fact that when one hundred varieties are root-grafted or budded on the same lot of seedling stocks, each variety when dug will how its characteristic roots. The Red Astrachan roots will be fibrous, branching out near the surface, with few deep roots; while the Duchess, Fameuse, and Hibernal will show few fibrous roots, but several pronged coarse ones, one of which, or more, runs deep into the subsoil. This is also true of the pear and other fruits. If the same pear-seedlings are grafted in part with Bartlett and a part with Onondaga scions the two varieties can be separated in digging by inspection of the roots alone.
The influence of the stock upon the top in root-grafted trees is not so apparent; but in top-grafting on varied stocks that are well established the effect on growth and fruitage is often very striking.