A Short Guide to Dwarfing Rootstocks

Image Gallery

Article Tools

Image Gallery

Print

E-mail

Comments

RSS

The Seasons of the Garden

Midsummer's merciless sun scorches down from the cloudless skies, and parched plants slowly lower their leaves as the earth bakes beneath them. When dusk descends and the first tentative fireflies flicker against the darkening horizon, water the soil to slake its thirst . . . and resolve that next year you'll make (and use!) much more moisture-holding mulch.

The rootstocks commonly used to create dwarf apple trees were developed, over a number of years, in England . . . first at the East Malling Research Station and later at the Merton Station (which explains why the prefixes M—or EM —and MM are used to designate the different varieties). These rootstocks can all reduce the tree size (but not the fruit size!) of a variety that's grafted or budded onto them . . . and they do so by simply limiting the amount of food that the tree gets. This same factor induces early bearing (often three or four years sooner than that of full-sized trees) by reducing the amount of vegetative growth. It seems that while there's leaf and limb growing to be done, the apple tree postpones setting fruit.

Depending on what rootstock you select and what apple variety you're budding, the eventual height of the tree can range from 6 to 25 feet. You should consider several factors in choosing one of the five rootstocks generally available: [1] the amount of land you can devote to apples and the number of trees you hope to have, [2] the nature and fertility of your soil, [3] the types of insects and diseases present, and [4] the vigor of the apple variety (or varieties) you want to grow. Here's a listing—arranged in order of dwarfing effect, from most to least—of a variety of popular rootstocks . . . and some of their advantages and disadvantages.

M-27 is really sort of a ringer: Although it's been under development for several years, it isn't yet available commercially. This superdwarfing rootstock produces container-sized apple trees that stand a minuscule 4 feet tall. Work is now being done on propagating the rootstock by tissue culture. When that's a reality, supplies should increase rapidly.

M-9 has the greatest dwarfing effect of any widely available rootstock. Trees grafted or budded onto it will usually grow to about 30% of their normal size, which means that the M-9 dwarf trees are between 6 and 10 feet tall at maturity. Apples will usually begin to bear in two or three years, and yield about 60 pounds of fruit when they're fully grown. You can cram these dwarfs pretty close, too . . . they're commonly grown on 10- or 12-foot centers. The rootstocks do have some drawbacks, though. For one thing, they tend to have a weak root system and to be somewhat brittle, so it's necessary to stake the trees to keep them from blowing over and perhaps snapping where they're grafted. (Many professionals bud these trees high—about 12 inches from the rootstock's original ground level—so they can be planted deeply for better anchoring.)

RSS | Comments | E-mail | Print