happen that the top part of a tree is limited in its climatic scope
because of its inability to withstand precipitate or otherwise
unfavorable temperatures. Having observed that certain grafted varieties
of fruit trees, such as the Wealthy apple, for instance, have gradually
come to be planted much farther north than they originally were, I
reasoned that this was because only the hardiest of them survived and
these hardy ones therefore became the mother blocks for future grafting.
This was an inescapable procedure which acted as a method of bud
selection. I therefore assumed that by a careful choice of the hardiest
among surviving twigs of the most recent graft of the Harriet apricot,
when particularly severe winter weather had caused some injury, I could
induce extra-hardiness in future grafts.

I also believe that I have added to the hardiness factor of the apricot
by making frequent grafts. It is my theory that the root stock is able
to exert some influence over the top other than mere maintenance of
life. By frequently uniting a hardy stock with a less hardy top, I think
that the individuality of the top part may be somewhat broken down and
the extra characteristic of hardiness added to it. After the fifth
re-graft of this apricot made in eight years, I am convinced by its
appearance and behavior that it is capable of becoming a reliable
apricot for the region around St. Paul. Today the apricot still exists
grafted on plum at my nursery at River Falls, Wisconsin, and the
weakness of the tree seems to be in the union between the top and the
plum stock. If this union were not so corky and large and succulent it
might be less injured by our winters; therefore it is quite apparent
that the plum is not a congenial stock for an apricot, at least it does
not produce a satisfactory union. I am now making tests with this same
variety by grafting it on more hardy apricot seedling stock such as the
Prof. N. E. Hansen of Brookings, South Dakota, introduces.