The rootstock you choose for your new orchard will have a large impact on the performance of your trees, and the profitability of your investment. Apple growers have been using clonal rootstocks for more than 50 years, and much has been learned in that time. When researchers in England developed the Malling rootstock series, the tree size ranged from full-sized standard trees down to a fully dwarfed M27. For today's high density orchards, we prefer a tree size produced by the Malling 9, or M9 rootstock.

To add to the confusion, there are many different clones of M9 that have been selected over the years. EMLA 9 is from England, Pajam is from France, and Nic 29 is from Holland. In general, these rootstocks show more vigour than the original M9.

But rootstocks also affect other things about apple trees, including fruit size, disease susceptibility, maturity date, and winter hardiness to name a few. For example, we know that fruit produced on trees on M9 rootstock have larger apples than on M26 rootstock. But there are some major problems with M9 that have encouraged the search for a better rootstock.

M9 appears susceptible to winter injury, especially the commonly-grown strain NAKB337. This rootstock is highly susceptible to fire blight, and actually makes the tree itself more susceptible to fire blight infections. M9 is not a good choice in orchard replant situations, and in fact, may not have enough vigour for slow growing trees like Honeycrisp. So we are testing other rootstocks from around the world, looking for better performance.

Budagovsky 9, or B9, comes from Russia, and is very winter hardy, but has some disease issues. Researchers in New York are now releasing new rootstocks from their Cornell-Geneva breeding program which focuses on disease resistance and replant tolerance. At this point, there are now 3 Geneva rootstocks available: CG 16, CG30 and CG11, with more under development. Also, a series of rootstocks produced in Vineland are under test and it appears that V3, V5 and V6, are similar size to M9. V1 and V2 are similar size to M26, so may be useful where stronger growth is needed.

With so many rootstocks to choose from, a careful evaluation of research results and field experiences will be important to select the ideal one for your orchard. The rootstock must also be matched with the correct tree density to maximize yield efficiency. Growers need to work with their nursery suppliers to order trees well in advance of their planting year, so they can get the rootstock that will give them a performance edge in new orchards.