In spite of their wide geographic distribution, the various species in the genus Pyrus are intercrossable without major incompatibility barriers. Also, the high morphological diversity and the lack of distinguishing characters among the species have been reported. Therefore, the classification of species in this genus is problematic and often confusing, giving different populations designated as different species by some authors. It is likely that, when the genus is reviewed, there will be several changes to the nomenclature[
Pyrus dimorphophylla Makino
Pyrus kawakamii Hayata
Pyrus koehnei C.K.Schneid.
Pyrus mairei H.Lév.
Common Name: Callery Pear
Flowering tree a the Morton Arboretum, USA
Photograph by: Bruce Marlin
Pyrus calleryana is an unarmed, deciduous tree with a narrow, conical crown, it usually grows 5 - 8 metres tall, sometimes reaching 15 metres tall but sometimes only a shrub[
The tree is harvested from the wild for local use as a food and source of materials. It is widely used as a rootstock in China and is also often grown as an ornamental.
The cultivar 'Bradford', which produces sterile fruits, has been widely planted throughout the United States since the early 1900s, but recent cultivars, which have been bred to reduce the tendency of the tree to split in snow or high winds, have produced viable seeds. These seeds have been spread into the envoronment by fruit-eating animals, especially birds, and plants developing from these seeds have become established in various areas of eastern N. America. Pyrus calleryana often invades disturbed areas and can disrupt the establishment of middle to late successional species, sometimes forming dense thorny thickets that are impenetrable to humans[
The pollen can be bothersome to people with allergies[
Although no specific information has been seen for this plant, the seed of many species in the family Rosaceae are likely to contain cyanogenic glycosides. When injested, these compounds break down in the digestive tract to release cyanide. Used in small quantities in both traditional and conventional medicine, this exceedingly poisonous compound has been shown to stimulate respiration, improve digestion, and promote a sense of well-being[
]. It is also claimed by some to be of benefit in the treatment of cancer - though this claim has been largely refuted.
In larger concentrations, however, cyanide can cause gasping, weakness, excitement, pupil dilation, spasms, convulsions, coma and respiratory failure leading to death[
The levels of toxin can be detected by the level of bitterness:- sweet almonds, for example, contain only very low levels of it and are safe to eat in quantity, whilst bitter almonds (which are used as a flavouring in foods such as marzipan) contain much higher levels and should only be eaten in very small quantities. Great caution should be employed if the taste is moderately to very bitter[
E. Asia - southern and eastern China, central and southern Japan, northern Vietnam.
Thickets and streamsides; at elevations up to 1,500 metres[
]. Slopes, plains, mixed valley forests and thickets; at elevations from 100 - 1,800 metres[
|Other Uses Rating
|Cultivated, Ornamental, Wild
Pyrus calleryana is a very cold-hardy plant, tolerating temperatures down to around -40°c when dormant[
Prefers a good well-drained loam in full sun[
]. Grows well in heavy clay soils. Tolerates light shade but does not fruit so well in such a position. Tolerates atmospheric pollution, excessive moisture and a range of soil types if they are moderately fertile[
]. Established plants are drought tolerant[
]. Grows well on acid soils[
There are many named forms selected for their ornamental value[
]. The cultivar 'Bradford' is a dense, vigorous tree that is resistant to fireblight, though it has a tendency to split in snow or high winds[
Plants are moderate to fast growing[
Resists fireblight, collar rot, root aphis, pear psylla and root lesion nematodes[
]. This species is resistant to most important diseases and pests. For this reason, several different cultivars had been selected as street trees[
Trees have a short dormancy period and lose their leaves late in the season[
Fruit - raw or cooked[
]. Best used after it has been exposed to frost[
], since this will soften and sweeten the flesh[
]. The globose fruit is blackish-brown with pale dots about 10 - 25mm in diameter[
This species is widely used as a rootstock[
], especially for cultivars of Pyrus pyrifolia[
]. It is resistant to most important diseases and pests, and is said to induce earlier bearing[
The wood of this species is hard and close-grained, and is sometimes used for making furniture and stools[
Seed - best sown in a cold frame as soon as it is ripe in the autumn, it will then usually germinate in mid to late winter. Stored seed requires 8 - 10 weeks cold stratification at 1°c and should be sown as early in the year as possible[
]. Temperatures over 15 - 20°c induce a secondary dormancy in the seed[
]. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in light shade in a cold frame or greenhouse for their first year. Plant them out in late spring or early summer of the following year.