Chinquapin hybrids from a tall growing tree. Nuts grow in racemes of burrs with as many as 10 burrs on one stem. Photo by C. Weschcke.
Apricot
If it were not that an apricot is a nut as well as a fruit, I should hesitate to include a description of my work with it. But the apricot seed has a rich kernel which, in many countries, for example, China, is used as a substitute for the almond to which it is closely related.
It was in 1933 that my aunt, Margaret Weschcke, told me of an apricot tree growing in a yard on the Mississippi River bluff in St. Paul and said to be bearing fruit. I was quite skeptical until I saw the tree and also saw fruit from it which had been preserved by the woman who owned it. Convinced of the hardiness of the tree, I was anxious to obtain scionwood but it was not until late that winter that I received permission to do so. It happened that a truck had broken off a large branch from the tree while delivering coal, and the owner very reasonably decided that taking a few twigs from it would not hurt it any more. I not only took the small branches that she was willing to sacrifice from her tree but also as many as possible from the branch which had been torn off, as its terminals were still in a fresh condition.
I grafted these scions on hybrid plum trees where they took hold readily, and in 1938, they began to bear prolifically. The apricots, which I have named Harriet, in honor of my mother, are a fine-flavored fruit, medium in size. Their cheeks are a mottled red with raised surfaces. Their pits are well-formed and fairly edible. Although the parent tree died the winter I took scions from it, my grafts have proved quite hardy, having received no injury when temperatures as low as 47° below zero have occurred. Since the parent tree died because its roots were severely frozen, it would seem that the top of the tree, in this case, was more hardy than the root system. This does occur sometimes, although it is unusual.
In developing the factor of hardiness further in this apricot variety, I have taken advantage of something I had observed about other fruit trees. When one combines parts of two trees by grafting, it is a simple thing to select a hardy root stock from the available plants, just as I selected hardy plum stock on which to graft my apricot scions. This is not always possible in choosing scionwood, however, since scionwood is usually selected for such reasons as the quality of its fruit. It may 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.