Rootstock

Most fruit trees, if left to their own devices, will grow to be quite large. For instance, pear and apple trees grow to be about 40 feet tall, and require an additional 40 feet of space around them. They take up a lot of space, and they require a ladder to prune or harvest them.

The way that apple and pear trees are made to grow smaller is by using different rootstocks. Since apples and pear seeds are not like their parents, sticks called scions from a parent tree are grafted onto different rootstock to control their size. Some rootstocks will dwarf a tree down to only 6 feet tall! Apple rootstock sizes are usually classified as standard (taller than 15 ft), semidwarf (up to 14 feet), and dwarf (less than 9 ft).

In addition to not getting so tall, the trees do not get as wide and require as much space. Therefore, in an area required for a 40 ft tree, one could plant nine dwarf trees or five semi dwarf trees.

Besides looking at how tall a tree might get when planning on buying a tree on rootstock, take into account the rootstock needs. Some rootstock prefer one kind of soil over another, prefer a specific range of pH soils, require more water, or thrive better at different temperatures. Some rootstock are even more disease resistant than others.

Other benefits to size controlling rootstock also take less time to mature than standard root stock. Since they are smaller, they require less equipment such as tall ladders and pole trimmers. Their small size also means that the care of one tree can be done in less time. And, since apples and pears are not self pollinating, other trees that can pollinate to bear fruit are closer, making pollination more likely to happen.

My two custom grafted apple trees were done onto M9. Out of what the Home Orchard Society offered when I ordered these trees, I felt this would reach the most ideal height for what I wanted. For an actual orchard, they would probably be too tall, but we wanted a little bit of shade on our house, so we opted for something a bit bigger.

For more information regarding size controlling rootstock, including other kinds of fruit, please read the Washington State University’s free paper titled Fruit Handbook for Western Washington.