Meet the Asian Pears
Perhaps it's no surprise that Asian pears suffer an identity crisis. Are they apples or pears? Like apples, they ripen on the tree and have a crisp, firm texture, but they have juicy, white flesh with the flavor and fragrance of pears. Since their introduction to this country more than a century ago, these fruits -- primarily descendants of two Asian pear species, Pyrus pyrifolia and Pyrus ussuriensis -- have been commonly known as apple pears. They have also been called sand pears, Oriental or Chinese pears, sha li (Chinese for sand pear), and nashi (Japanese for pear).
Asian pears are deliciously sweet and low in acidity, and each variety has a distinctive bouquet. In China, Japan, and Korea, thousands of different varieties are cultivated, and even in this country, a few dozen varieties are commercially available. Among these are a cornucopia of flavors; some, like 'Yoinashi', are as smooth as butterscotch, while others, such as 'Seuri', have the subtleness of apricot. A few are spicy, including 'Shin Li', which has a hint of cinnamon.
The fruits may be smooth and thin-skinned, in colors ranging from moonlight yellow, and yellow-green, to caramel, or they may be russeted shades of these.
Because of Asian pears' increasing popularity, more varieties than ever are available to home gardeners. And that's good news, because Asian pears sold commercially are often picked before they are ripe. Unlike European pears, Asian pears must be tree-ripened for peak flavor and sweetness. Once picked, the fruits will not ripen further. By growing your own, you can decide when the fruit has reached peak flavor.
Although fruit flavor is a major factor when selecting varieties, consider also disease resistance and hardiness, which are determined in large part by the rootstock. As a rule, Asian pears do well in the same places as European pears. They grow in USDA Hardiness Zones 5 through 9, though some varieties, such as 'Seuri' and 'Ya Li', are hardy to zone 4. Typical chill requirements range from 300 to 600 hours (for trees to fruit and grow properly, they require a minimum number of hours with temperatures that fall below 45 degrees F. but remain above freezing). 'Hosui', 'Shinseiki', and 'Twentieth Century' are least chill sensitive and are best suited to warmer regions such as zone 9.
While most Asian pears are partially self-fruitful, they'll produce more and larger fruits with cross pollination. Plant more than one variety, or if space is limited, choose a tree that includes several grafted varieties. Although it's a European pear, 'Bartlett' is a good pollinator. Check with the nursery to confirm that the bloom periods coincide and pollen is compatible for the varieties you select.
Before making a decision on a variety, consider its susceptibility to fire blight and bacterial canker, bacterial diseases influenced primarily by weather and prevalent in regions with rainy, humid springs and summers.
Flavor varies depending on climate (summer warmth helps to sweeten flavor) and harvest time. Even water and soil conditions can affect flavor. Many growers agree that adding trace minerals, such as rock dust, to the soil results in better-tasting fruit.
Some varieties may also be better adapted than others to your growing area. In my zone 8 orchard with heavy clay soil, 'Hosui' has never fruited, while 'Shinko' and 'Shin Li' produce abundantly.
Paring Down the Choices
To help get you started, here's a rundown of popular varieties; all, except 'Chojuro', are well suited to home gardens. All produce round fruit and are Japanese varieties unless otherwise noted. Ripening dates are given for zone 8 and will vary from two to four weeks earlier in zone 9, and one to three weeks later in zones 5 to 7.
'Hosui', a rosy gold russeted medium to large fruit with tender, sweet white flesh, wins many taste surveys. Its rich flavor, brandy aroma, and low acidity are the reasons for its popularity. Fruit ripens early to mid-September and keeps up to two months. Susceptible to fire blight and bacterial canker.
'Kikusui' has delicate yellow-green skin with a delightful sweet-tart white flesh that's crisp and juicy. The very productive trees produce medium-sized fruits. Fruit ripens in early to mid-September and keeps very well, up to five months. Very susceptible to fire blight.
'Large Korean' produces enormous fruits (up to a pound) with bronze russeted skin and juicy, sweet white flesh with an unusual earthy flavor. The fruits, prized for both their size and flavor, are also sold as 'Dan Beh', 'Korean Giant', and 'Olympic'. Fruit ripens late, about mid-October, and keeps up to five months. Excellent resistance to fire blight.
'Seuri' has dark orange skin and delicious, crisp, fine white flesh with hints of apricot. The fruits of this Chinese variety are large, round, and sweet. It is a low-chill, early blooming variety that should be pollinated by 'Ya Li', another early bloomer. Fruit ripens late September to early October and keeps about one month. Trees are susceptible to fire blight skin with russet overtones and wonderful sweet yellow-white flesh that is richly flavored and subtly fruity. Fruit flavor is excellent, especially in hot climates. This variety is very productive and needs heavy thinning to produce large fruits. Fruit ripens in late September to early October and keeps two to three months. Very good resistance to fire blight.
'Shin Li' has medium smooth, yellowish green skin with russet spots. The firm white flesh is extremely flavorful and has a sweet and spicy, cinnamon-like aroma. The very productive trees yield large fruits like slightly flattened spheres. Fruit ripens in early to mid-October and keeps three to four months. Very susceptible to fire blight.
'Shinseiki' has smooth, moonlight yellow skin and delicately sweet, firm-textured juicy white flesh. The medium to large, faintly aromatic fruit is also sold as 'New Century'. Fruit ripens in late August and keeps three to five months. Moderate resistance to fire blight.
'Twentieth Century', also known as 'Nijisseiki', has thin, bright yellow-green skin with juicy-crisp white flesh. The mildly aromatic, very sweet fruit with a touch of tartness is the most widely grown variety worldwide. It is vigorous and reliably produces medium-sized fruits. Fruit ripens in late August and keeps three to five months. Susceptible to fire blight.
'Ya Li' is a popular pear-shaped Chinese variety with tender green skin and mildly tart flesh. This early-blooming variety requires another early bloomer (such as 'Seuri') for pollination. The trees are vigorous, productive, and hardy. Fruit ripens in early September and keeps up to five months. Moderately susceptible to fire blight.
'Yoinashi' is a golden brown-skinned variety with outstanding juicy, off-white flesh with crops of medium to large fruits. Fruit ripens in mid- to late September and keeps up to three months. Trees appear to resist bacterial canker but are very susceptible to fire blight.
Gardeners are also likely to encounter 'Chojuro', an older variety with astringent orange russeted skin and full-bodied, drier yellow-white flesh. Although it's still widely sold, it is now considered inferior. Under ideal conditions, which are difficult to pin down, trees yield good crops of medium-sized fruit that can vary in texture (smooth to grainy) and taste (rum-flavored to bitter) with each season. Fruit ripens mid- to late September and keeps up to five months but bruises easily. Moderate resistance to fire blight.
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.
Diseases and Pests
Several bacterial diseases can affect Asian pear trees. The two most common are fire blight (Erwinia amylovora) and bacterial canker (Pseudomonas syringae). The diseases look similar and are easy to spot: the infected branch or twig will look singed with scorched leaves remaining attached. Wet weather promotes both diseases, with fire blight thriving in warm temperatures and bacterial canker in cool ones.
If you live in a disease-prone region, select resistant varieties. Note, however, that disease resistance varies by region, soil conditions, and climate. If your tree is affected, prune infected branches 12 to 15 inches below the infection, and sterilize tools with alcohol or bleach between each cut.
A dormant oil spray will destroy many overwintering insects and even some diseases, but codling moth (Carpocapsa pomonella) requires more control. Careful fruit thinning helps, but the easiest and most effective control I've found is an annual release of parasitic trichogramma wasps. I release them when I see the first moths fluttering in mid-April, and again two to four weeks later. Releasing 5,000 wasps each time is sufficient for two to three trees. Before our release program, up to 30 percent of the fruit suffered codling moth damage. Now less than 5 percent is affected.
Expect a healthy young tree to produce 5 to 15 pounds of fruit, a 5-year-old tree 30 to 50 pounds, and a mature tree, from 100 to 400 pounds. Wait to harvest fruit until its background color has changed but the fruit is still firm, then begin tasting it for peak flavor. If the fruit is picked too soon, the sugars won't develop fully. However, don't wait until the fruit is soft, or it will be overripe and spongy. Never pull fruit off the tree; wait until it lifts off effortlessly. The tender skin also bruises easily, so handle fruit gently.
Asian pears keep up to two weeks at room temperature, and many varieties will retain their quality for up to five months in a cool, humid environment (about 34 degrees F.). The fruits also freeze and dry well. I prefer, however, to enjoy the crisp, juicy fruits in the cool of the morning -- right from the tree.
Kris Wetherbee has more than 100 trees of nine varieties of Asian pears in her Oakland, Oregon orchard. Photography by Michael MacCaskey.