Gardening Articles: Edibles :: Fruit & Nut Trees
Meet the Asian Pears (page 3 of 4)
by Kris Wetherbee
The Right Rootstock
Rootstock plays a key role in a pear tree's productivity, longevity, and hardiness. Incompatibility of rootstock and variety can result in poor growth and declining crops. Pyrus betulifolia is most widely used because it is long-lived, versatile, vigorous, and it tends to produce abundant crops and large fruits and resists fire blight. However, it is less tolerant of alkaline soils and extreme cold.
In cold-winter regions, choose P. ussuriensis, which is less vigorous but hardy to -40 degrees F. In zone 9, the best choice is P. calleryana, which resists fire blight, oak root fungus, and crown rot, but it is subject to pear decline.
Planting and Care
Late winter or early spring is the best time to plant bare-root trees. Choose a site with full sun and well-drained soil, ideally with a pH of 6 to 6.5. When mature, a typical 12-foot tree will have a span of 12 to 15 feet, so space trees 12 to 15 feet apart, making sure that the graft union -- which looks like a scar or knob near the base of the trunk -- remains 2 to 4 inches above the soil.
Water requirements vary depending on soil conditions and climate, but in all cases, trees need adequate irrigation to produce good-sized fruits. In many areas, summer rainfall is sufficient for mature trees, but young trees will need deep watering once a week. Trees 5 years and older can get by with less frequent watering. In my dry summer region of the Pacific Northwest (zone 8), each tree receives about 100 gallons of water every 7 to 10 days. A thick layer of organic mulch around each tree helps to retain soil moisture.
In early spring, apply a mulch of compost, and every three to five years dress with rock dust (for trace minerals). Go easy on the nitrogen. A good guideline is the 2-foot rule: If your trees are growing more than 2 feet per year, they are receiving too much nitrogen. This can result in diminished fruit flavor, susceptibility to bacterial diseases on young trees, and winter damage from tender growth.
Thinning and Pruning
Trees usually produce fruit the second or third year after planting. Fruit is borne on spurs, 1- to 3-inch nubby twigs, on 2- to 6-year-old branches. Soon after pollination, trees will set many fruiting clusters, sometimes with five to eight fruits. Thinning is essential for larger, more flavorful fruits and to prevent bearing in alternate years, reduce insect damage (two fruits touching provide an excellent area for codling moths to lay their eggs), and keep branches from breaking. Thin when the fruits reach cherry size; in Oregon, that's sometime in June. Depending on the intensity of fruit set, leave one fruit per cluster or every 6 inches.
Asian pear trees can be pruned in any of three methods: open center (vase), modified central leader, or espalier trellis. Prune lightly the first couple of years, just enough to shape the tree. Do heaviest pruning when the trees are dormant but after the danger of a hard freeze has passed. Always remove any dead, broken, diseased, or crossed branches. Remove all rootstock suckers or low-growing branches, and pinch the main stems to keep the height manageable. Some growers head them at 8 feet; others, who aren't averse to using a ladder, limit them to 15 feet.