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 turcomanica is an unarmed, deciduous tree with a braod, irregular crown; it can grow 10 - 15 metres tall[
The plant is harvested from the wild for local use as a food. It is often grown in its native range for use as a rootstock for the cultivated pears.
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[
Central and western Asia - Kyrgyzstan, Tajikistan, Turkmenistan, Iran
Dry stony slopes, occasionally in valleys, on deep alluvial soils[
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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[
Fruit - raw or cooked. Sweet with a resinous taste[
]. The thick-skinned fruits are broadly pyriform, around 25mm wide and 20mm long[
Widely cultivated in central and western Asia, it is used as a rootstock for different pear cultivars. Numerous cultivars exist with different degrees of domestication[
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.