Most retail nurseries and garden stores are now advertising a good selection of bareroot fruit trees. With visions of juicy red cherries, crisp, sweet apples and mouth watering plums, many gardeners choose trees based solely on the fruit they will produce. Rootstocks, however, are equally important.
A fruit tree is really made up of two varieties: the top variety produces the fruit we eat, and the bottom variety, called the rootstock, is mostly underground. The rootstock determines, among other things, the vigor and size of the top variety as well as the tolerance to various soil conditions, root anchorage, and how soon the tree will come into bearing. Selecting the right rootstock for specific spacing and conditions is just as important as finding the right top variety to produce the fruit.
Dwarf to semi-dwarf rootstocks are highly recommended for both backyard and commercial orchard planting. Trees on very dwarfing root-stocks are much easier to maintain and care for due to their smaller size. Fruit can be thinned and harvested mostly from ground level, and pest management is easier and less expensive when the total tree volume is smaller. A high-density mini-orchard can fit into limited areas, such as patios and courtyards, or can be narrowly espaliered along a fence line.
Some trees can even be grown in large pots or containers. Although they can be started in a smaller pot, trees grafted on the smallest rootstocks (e.g., apple trees on M 27 rootstock) will thrive permanently in a 25-gallon pot or half barrel. These trees can be very fruitful for their size and add an attractive artistic element to your landscape design. Small trees grown in containers can be more easily moved under cover during wet periods to avoid infection by rain-borne diseases such as apple scab, anthracnose, peach leaf curl and brown rot.
Training and support for trees is a factor in rootstock selection, since rootstocks with smaller, less vigorously growing roots need permanent support to keep the trees upright and maintain their fruit load. Also, some top varieties have a highly vigorous growth habit, while others are less vigorous. Even on a very dwarfing rootstock, a tree with highly vigorous habit will result in a larger tree at maturity than a less vigorous variety on the same rootstock. The combination of top and rootstock should be vigorous enough to provide good long-term fruit production, but not too vigorous to manage effectively. Optimum spacing for trees is determined by the size of mature trees, the major consideration in rootstock selection.
The rootstock variety determines how large the mature tree will be, not the size of the fruit. Therefore, when selecting trees to plant, it is important to know the specific rootstock variety as well as the top (fruit) variety. Just because the label says "semi-dwarf" doesn't mean the tree will be small. Invest your money in trees grafted on the right certified rootstock one that is suited to the space available and your solid conditions.
Additional information on rootstocks for pears, plums, prunes, cherries and peaches can be found in WSU's Fruit Handbook for Western Washington (EB 0937). Cost is $6.50 plus tax, shipping and handling. You can order a copy by dialing 800-723-1763 or logging onto http://pubs.wsu.edu.