A Short Guide to Dwarfing Rootstocks

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Apples budded to M-9 are susceptible to attack by nematodes, woolly aphids, and fireblight, so think twice about choosing this rootstock if any of these nasties are about. On the other hand, M-9 trees are resistant to collar rot, which means that they'll usually do reasonably well in wet or clayey soil. (Be sure to clear an area at least 2 feet in diameter when you plant one of these little fellers . . . mulch to keep weeds and grass from stealing all the food in the soil . . . and be prepared to irrigate M-9 trees during dry spells.)

M-26 is second to M-9 in dwarfing capacity. Trees on this rootstock usually grow about 40% of the standard height, producing dwarfs that range from 8 to 12 feet tall. The M-26 root system is stronger than that of M-9 (though staking is still necessary). The tree is hardier, too, and growth is more vigorous . . . especially in soils with poor fertility. M-26 is susceptible to collar rot, though (so don't plant it in wet or clayey soil), and fireblight and woolly aphids are also problems. It's best to place buds high, and to set out these dwarfs on a 10' X 18' grid

M-7A (the letter "A" indicates that this is a virusfree sibling of the original M-7) is a semi-dwarfing rootstock . . . producing sturdy, winter-hardy trees that are about 50% of standard size. These productive, early-bearing, 12- to 15-foot beauties should each produce over 100 pounds of fruit a year at maturity. Apples on M7A do well in most soils, even in clay. The rootstock is susceptible to suckering, but that tendency can be defeated if you bud high and plant deep. M-7A's aren't very drought-resistant and are susceptible to woolly aphids. They should be planted on a 12' X 20' grid.

MM-106 produces trees that are about 60% of normal size (usually 12 to 18 feet tall). This early-bearing, drought-tolerant rootstock is excellent for the naturally smaller, slow-growing spur apple varieties. M-106 trees are productive, root better than M-7A trees, and do not sucker. They are vulnerable to collar rot, though . . . so —once again—keep them away from wet or clayey soils. And if you're cursed with early autumn frosts, keep in mind that M-106 trees harden off late and are thus susceptible to freeze damage. Space these semidwarfs on a 14' X 22' grid.

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