The dream of every amateur gardener is to plant and grow dwarf apples and pears in their garden.
Dwarf trees, in comparison with vigorous ones, have a number of significant advantages: smaller tree size, placement of more trees in the same area, earlier onset of fruiting, higher productivity per unit area, larger fruit size and better quality, smaller root system , allowing the cultivation of such trees in low marshy areas with a high standing of groundwater.
Growing dwarf fruit trees, however, presents significant challenges. First, you need to have dwarf clonal rootstocks obtained by rooting cuttings or lignified and green cuttings, which takes at least two years. You can also graft on dwarf inserts, 15-20 cm long, previously grafted onto ordinary seed stocks, which also takes at least two years. Secondly, dwarf rootstocks and inserts have very fragile wood, and very often, after strong winds, the trees grafted on them break even in the nursery, which requires them to be bound to stakes. In addition, the winter hardiness of wood and roots of existing clonal rootstocks is not very high.
Is it possible to somehow get a bonsai from a young fruit tree, vigorous? It turns out you can. I first read about this in 1963 in the then newly published book "Reproduction of Garden Plants" by the American authors H.T. Hartman and D.E. Koestler. By the way, I consider this book to be the best book on this subject published to date. In the spring of 1964, I already laid down an experiment on such a transformation of 6 vigorous grafted trees (4 two-year-olds and 2 three-year-olds) and continued it until 1972.
What is the essence of such a transformation? At a height of 20-25 cm from the soil surface, a strictly horizontal annular bark incision is made on the tree trunk, and here, but already 10-15 cm higher than the first incision, a similar parallel bark incision is made. To better maintain horizontality, a cardboard template can be used, which is wound on a tree trunk before cutting the bark. From the upper annular incision to the lower, a vertical incision is made, thereby violating the integrity of the bark ring. On the ring, mark the top and bottom with a ballpoint pen, felt-tip pen or other writing object. Then carefully use a grafting knife to separate the bark from the wood along the entire perimeter of the ring, remove it and, turning it upside down, insert it into its original place. The ring should fit snugly against the wood.
To do this, it is tightly tied with twine, and the wounds are covered with a pitch or wrapped "with an interference" with strips of rubber (in this case, the pitch may not be used). To reduce transpiration, it is advisable to also wrap the wound with strips of plastic film. The following strapping technology can also be applied. Initially, fasten the ring with small small nails, and then, since when the bark ring is wrapped with twine or rubber, the bark is partially injured, it is advisable to first wrap the bark ring with strips of plastic film and only then wrap it with twine or rubber over it. The film and the tourniquet are applied so that they grip well both the upper and lower ends of the ring. Such an operation works best in early spring at the beginning of sap flow at the time of swelling of the kidneys. The operation is not so difficult and can be easily carried out by any amateur gardener with basic grafting skills.
As a result of such grafting, due to a change in the normal polarity of the bark ring, there is a difficulty in transporting the growth substance - auxin and photosynthetic products to the root, which leads to the effect of tree dwarfism.At the same time, the size of the crown and root is significantly reduced, the onset of fruiting is accelerated, the fruits are enlarged and the yield increases. But this eliminates the low winter hardiness and fragility inherent in clonal rootstocks.
However, such an operation can be fraught with some troubles. So, with a wide ring, the effect of dwarfism can be so strong that the root will simply starve and be unable to feed the crown. Usually, wild shoots grow on the trunk below the grafting site, which are not affected by the ring. These shoots also feed the roots with photosynthetic products. By regulating the number and size of these shoots, you can achieve normal root nutrition and normal crown growth. In the case of a narrow ring, it sometimes happens (usually after 2-3 years) that normal conductivity of the pathways is restored in the phloem of the bark of this ring, and the tree begins to grow strongly again.
When setting up my experiment, I used rings 10, 15 and 20 cm wide, using two trees for each ring. Indeed, already in the first year, by the end of the growing season, there was a sharp decrease in the growth of all shoots and the setting of fruit buds. On trees with a wide ring of bark, shoot growth was minimal. In the second year after the operation, all the experimental trees began to bear fruit, the size of the fruits on them was indeed somewhat larger. Starting from the first year, the growth of wild-growing shoots was observed on all trees below the grafting site, and above - the influx of different sizes. By the fifth year, one tree with a 10 cm wide bark ring, and by the seventh year, another tree with the same ring width began to give large increments, characteristic of vigorous trees, i.e. have lost the property of dwarfism.
One tree with a bark ring of 20 cm for two years had a depressed state and a very large influx above the graft site, its growth was minimal, and fruiting was very poor. Strong starvation of the root of this tree was clearly observed. After growing a significant number of shoots below the grafting site in this tree, most of them were left to feed the root. As a result, the tree straightened and began to grow and bear fruit normally, like other experimental trees. Until the end of the experiment in 1972, all trees that showed dwarfism, with a reasonable number of wild shoots, grew well and bore fruit. In 1972, during the uprooting of the garden, two of these trees were dug out to study the root system. It turned out that the size of the root system really decreased in comparison with that for vigorous trees.
For trees that have shown strong growth again, a second operation can be done, but not on the trunk, but on the skeletal branches of the crown. In addition, to prevent such a return to vigorous growth, it is advisable to work with a ring 20-25 cm wide.
