Pear & Asian Pear Pyrus communis L.; Pyrus pyrifolia (Burm.) Nak Rosaceae

Species description Pear trees are deciduous with a tall, strongly upright to spreading form. The alternate leaves have a glossy texture and finely serrated margins. The white, perfect flowers (containing both male and female elements) are borne in terminal clusters. The flowers are primarily self-incompatible, meaning they require cross-pollination to set fruit. Pear fruit varies in shape from oblate to pyriform. Asian pears are more rounded in shape with crispy, aromatic flesh.

Natural and cultural history The pear genus most likely originated in the Tian Shan Mountains of western China; Nicolai Vavilov describes three main centers of diversity: China, Central Asia, and the Near East. Though the genus has more than twenty species, only a handful are edible and grown for their fruit, including European pears (P. communis), and Asian pears (P. pyrifolia), and minor species including P. ussuriensis, P. bretschneideri, P. pashia, and P. sinkiangensis. Asian pears were first cultivated in China 2,000 years ago and wild genotypes were preferentially selected for fruit as early as 3,300 years ago. In Greece, Homer writes in 1000 BCE that European pears are “gifts of the gods,” and grafting of named cultivars was documented in Greece 371-286 BCE.

Planting considerations and propagation techniques Pear trees grow from 30 to 60 feet in height, with a canopy breadth of 15 to 25 feet. Trees may live for 150+ years. They require 200-1500 chill hours for fruit set, depending on the variety and are best suited for growing in the central mountains of Arizona. Common pear varieties are cold hardy down to -25ºF, though early flowering varieties bloom one to three weeks before apple trees and are sensitive to late spring frosts. Pears mature in as few as 90 days, or as many as 200 days. Pear trees require full sunlight for fruit production. Pear flowers may be self-fertile, though most need to be cross-pollinated with at least two varieties present to produce fruit. Honeybees and native bees, including several species of solitary bees serve as effective pollinators. Pear trees grow on a wide range of soil types, but prefer well-drained soils. They grow best with a soil pH range of 6.2-6.8. Pear varieties are generally propagated through grafting. Pear cuttings are difficult to root but dormant hardwood cuttings can be rooted if treated with rooting hormone. Layering, by bending young branches into moist soil, can also be used for clonal propagation. Seeds must be stratified at 39ºF for 60 to 90 days before germination will occur; seedling pear rootstock are typically grown for grafting standard sized trees. Other species are utilized for rootstocks for Asian pears and for more difficult soils and climates. P. betulifolia is used in clay and poorly drained soils and is a common rootstock for Asian pears. P. ussuriensis is useful for high pH soils and is exceptionally cold hardy. Quince may be used as a dwarfing rootstock for European pears, though these are also susceptible to fire blight and not well anchored, and many pear varieties are incompatible with quince.

Water needs Pear trees require an inch per week to establish young trees, and in the growing season once they mature.

Care Pear trees are typically trained to a central leader with a pyramid canopy, though tall trees may be difficult to harvest. Dwarf trees are often grown on a trellis or espalier. European pears tend to have an upright growth habit with narrow angles between branches, and spreaders may be necessary in young trees for correct form. Fire blight (Erwinia amylovera) is a serious bacterial disease in most pear varieties, especially in warm, wet springs. Young shoots, blossoms and fruits are most affected—they turn black and wilt. Pear trees may also be affected by pear psylla (Cacopsylla pyricola), aphids, mites and powdery mildew. To treat these diseases, remove all the infected plant parts and destroy them. Do not compost any infected plant, as the disease can still be spread by the wind or through infected soil.

Harvesting and processing Ripe pears will be firm and sweet. Harvest ripe pears by hand with an upward, twisting motion. The fruits bruise easily and must be handled carefully. Asian pears damage most easily and should be picked into trays to cushion the fruit. Ripen pears at room temperature for the best quality. Pears are mostly consumed as fresh fruit, but may also be cooked, dried, juiced, or fermented into alcohol.

References and resources Bell, R.L. 2008. Pyrus spp. pear, pp. 733-745. Eds. Janick, J. and R.E. Paull. The Encyclopedia of Fruit and Nuts. CABI Publishing, Cambridge, MA. Morgan, J. 2015. The Book of Pears: The Definitive History and Guide to Over 500 Varieties. Chelsea Green Publishing, White River Junction, VT. Plants for a Future (PFAF). n.d. Pear – Pyrus communis L. www.pfaf.org/user/Plant.aspx?LatinName=Pyrus+communis Rieger, M. n.d. Pear – Pyrus communis, Pyrus pyfifolia. http://www.fruit-crops.com/pear-pyrus-communis-pyrus- pyfifolia/

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