Updated, Wednesday, January 20, 2016
The vast majority of fruit trees we grow consist of two trees-in-one — a fruit variety such as Gravenstein apple or Bing cherry, grafted on to a rootstock variety. The part of the tree above the graft union is known as the scion and the part below the graft union is known as the rootstock. Rootstocks determine several qualities of the fruit tree which sits above it, the most important of which is size. A super-dwarfing apple rootstock will produce an apple tree about 6′ high, for example, whereas a ‘standard sized’ rootstock can produce an apple tree 25′ high.
Generally, rootstock is the primary factor determining tree height, though other factors play a role – the vigor of the variety grafted on the rootstock, soil fertility, climate and irrigation practices. Pruning also has a great impact on size. When the tree has reached the height that you want, the easiest, most effective way to keep trees at that height is through summer pruning. Here’s how to guesstimate spacing between your fruit trees.
Here are the mainstay rootstock varieties we will have available at the 2016 propagation fair, with a smaller selection of other rootstock varieties available to meet specific requirements.
Dwarfing Apple Rootstock
Mature height 6-10 ft. A good all-purpose rootstock for the small garden. Resistant to Fire Blight and Crown Rot. It should be staked when young, especially in looser soils, and a permanent stake is useful. Best for a stand-alone tree with a single central leader. Not well suited to espalier.
Mature height 10-13 ft. The advantage of this rootstock is an early, heavy production of quality fruit. Generally it is free standing (does not require staking) but with heavy fruit set can lean in very windy areas. Also works well for an espaliered tree. Good in areas with frequent spring freezes, due to its delay in spring bud development. It has little tolerance of heavy, excessively acid, or unusually wet or dry soils.
Semi-dwarfing Apple rootstock
Mature height 12-16ft. One of the most desirable rootstocks when factors such as production efficiency, longevity, ease of propagation, hardiness, compatibility and disease resistance are considered. It has exceptional winter hardiness and good anchorage, but may require staking while young if in an open, windy area. It does well in most soils, especially deep, fertile soil versus light sandy or heavy clay. Good for high lead arsenic residue soils and old orchard sites with replant problems.
Semi-standard Apple Rootstock
Mature Height 18-22ft. with recommended 16-26ft. spacing. Excellent anchorage, with no staking required. Very drought tolerant and adapts to sandy and clay loam. Best Semi-Dwarf for heavy or poorly drained soils. Produces an early and prolific fruit crop.
Semi-Dwarfing Pear Rootstocks
Mature height 12-18 ft. In very recent years, Old Home Farmingdale 87 has emerged as the favored semi-dwarfing rootstock of choice among knowledgeable pear growers. The OHxF selections are compatible with most pear varieties and are known for their tolerance to blight and decline, and produce precocious (early-to-bear), well-anchored, very productive trees. Not vigorous enough for Asian Pears.
Mature height 15-20 ft. Resistant to fire blight, collar rot, woolly pear aphids and pear decline. Precocious, well-anchored, very productive trees. Does not sucker. Does well on a variety of soils.
Dwarfing and Semi-dwarfing Stone Fruit Rootstocks
(Plum, Prune, Apricot, Peach, Nectarine, Almond)
Slightly dwarfing, 10-15 ft. Moderately resistant to Phytophthora crown and root rot and oak root fungus, tolerates wet soils, root-knot nematode resistant. Should be staked the first couple of years as it tends to have fairly shallow roots when young and tends to lean. It does very well in wet soils and tolerates a variety of soil types.
St. Julian ‘A’
Slightly dwarfing. Plums, peaches and nectarines from 12-15ft. St. Julian is compatible with all varieties of Prunus trees. Drought tolerant, it will tolerate a wide variety of soils. Very productive and well-anchored it has a highly-regarded, popular, well-proven history in Oregon.
Standard Cherry Rootstock
Mazzard is especially suited for sweet cherry and tart cherry planted in wet and heavy soil types. Especially well anchored. Mazzard, the most popular cherry rootstock grown in America, is widely used through the PNW. 20-25′.