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[
Ficus pyrifolia Burm.f.
Pyrus serotina Rehder
Common Name: Sand Pear
The two fruits in the centre are the Ya pear (Pyrus bretschneideri), the two on the outside are different cultivars of Pyrus pyrifolia - Shinko on the left and Whangkeum on the right
Photograph by: Jjok
Pyrus pyrifolia is a deciduous tree that can grow 7 - 15 metres tall[
This species is often cultivated for its edible fruit, especially in China. Many varieties of pear cultivated in the regions of the Chang Jiang and Zhu Jiang rivers belong to this species[
]. The plant also has a range of medicinal uses and a useful wood.
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, northern Laos, northern Vietnam.
Warm rainy regions; at elevations from 100 - 1,400 metres[
]. Naturalized in low mountains and around villages in C. And S. Japan[
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Pyrus pyrifolia is a very cold-hardy species, tolerating temperatures down to at least -15Â°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[
A parent of the cultivated Asian pears[
Fruit - raw or cooked. Hard and gritty[
]. Firm crisp and juicy when fully ripe, they are eaten out of hand or used in fruit salads, pies or baked etc[
]. The subglobose fruit is brownish with pale dots; it can be 20 - 30mm in diameter[
]. Up to 5cm in another report[
]. The average yield from wild trees in the Himalayas is 83kg per year, though some trees yield up to 200kg[
]. The fruit contains about 4.9% sugars, 3.2% protein, 0.9% pectin[
The fruit is considered to be febrifuge, nervine, pectoral[
The leaves are astringent[
The bark is antiseptic[
The flowers are used in cosmetic preparations[
The wood is of good quality. It is used for making furniture[
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 1Â°c and should be sown as early in the year as possible[
]. Temperatures over 15 - 20Â°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.