Apples do not reproduce true to seed; if you plant a seed from a good apple the tree it produces will bear apples, but they may taste much different than the one the seed came from, and usually taste terrible, like grass or cotton. The only way to get a tree identical to the one the apple came from is to clone it by grafting, where a piece is taken from that tree and grafted onto another tree's roots. These roots are called the "rootstock" or "understock".
For centuries rootstocks were grown from common apple seeds from eating apples. They can make a very vigorous tree with deep roots that are adaptable to poor soils and drought. But since each seed is a different variety, the performance of the rootstocks can also be variable, some doing well and others poorly. So over the years apple varieties were identified that produced seeds that bear pretty close to type, where the seeds produce almost the same tree every time that has uniform, vigorous, well-adapted roots. Bittenfelder and Grahams Jubilee were the variety used in Europe and Antonovka favored in Russia for 500 years because it withstood the harsh winters. These two varieties are still favored for growing rootstocks from seed and produce a long-lived tree, 100 years or more. Seedling rootstocks have the added benefit of being considered virus-free.
However clonal rootstocks have been also used for centuries, varieties valued because they produce a smaller tree, which is called "dwarfing" or "size-controlling". These rootstocks must be propagated vegetatively through mound layering or stoolbeds, where the tree is cut back severely causing it to send up suckers, which are then rooted in sawdust. Because they are propagated vegetatively there is the possibility of passing on viruses from parent to offspring, and so the best suppliers carry stock that has been cleaned up by virus-indexing and field-tested often for viruses (virus certified). The dwarfing effect of clonal rootstocks is measured against a tree on seedling rootstock, which is considered 100% and can be between 8-10 meters tall.
Tropic conditions have a dwarfing effect on apple trees, and size control is not often an issue. Apples are grafted onto both seedling and clonal rootstock and easily kept to three meters tall by culture methods such as inducing heavy cropping. Some clonal rootstocks have the added benefit of being resistant to wooly aphid, an underground pest in some locations. There are are some very dwarfing rootstocks that produce a tree 1.5 to 2 meters tall, but they are very delicate, drought susceptible, and poorly anchored and not recommended for the tropics.
The rootstocks we offer are:
-M111 EMLA A slightly-dwarfing clonal rootstock that produces a tree 80% the size of a seedling tree (but this may vary widely depending on the variety, crop load, and culture method). It is particularly adapted to drought conditions and is very well-anchored. It imparts some slight early-bearing characteristics and is adaptable to worn out, sandy, or clay soils, but not as much as seedling rootstocks are. It has been used successfully in the tropics for years and will start bearing in 3 to 5 years, much earlier however with tropic varieties like Anna.
The "EMLA" designation at the end means it has been virus-indexed and all our suppliers are virus certified. It has a tendency to form aerial burr knots, visible on the trunk in the photo on the left, where it tries to form roots above the ground, causing rough patches of stubble on the trunk. Because of this it should be planted deep, the graft union just above the ground, as the burr knots give insect pests a place to hide. It is resistant to wooly aphid, an underground pest that causes nodules on the roots that slowly starve the tree.
-Seedling Our seedling rootstocks are on Antonovka, Grahams Jubilee, or Bittenfelder, all equally as good for producing a healthy, vigorous, long-lived tree. They produce the most drought-tolerant and adaptable tree, tolerating heavy clay or light sandy soils, and soils with fertility problems. It is well-anchored and can live a long time. With some varieties bearing can be delayed for 4-6 years, but Anna, Dorsett Golden, and Shell of Alabama will bear the second year even on seedling rootstock. You will notice a difference in the root structure when compared to a dwarfing rootstock like M111; the roots on the M111 look like strands on a mop, where on seedling rootstock they resemble ropes or cables, much more wild and tough-looking. They can go down 10 meters in good soil, but will not go very deep in heavy clay soils.
Photos: P18 clonal rootstocks, Winesap tree on seedling rootstock at Cantebury Shaker Village in New Hampshire, Red Topaz on Bud. 9 dwarfing rootstock, M111 rootstock tree, Antonovka seedling rootstock ready for grafting
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