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 regelii is a deciduous shrub or a small tree with widely spreading branches and long, slender spines; it can grow up to 10 metres tall[
The plant is harvested from the wild for local use as a food. It is used in semi-arid regions as a rootstock for the cultivated pear and also in reforestation projects. It is sometimes grown as an ornamental in gardens.
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[
W. Asia - Turkestan.
Dry stony slopes, rocks, sometimes in valleys on deeper moist soils, at elevations from 1,000 - 2,000 metres[
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Pyrus regelii is a very cold-hardy species, tolerating temperatures down to at least -15°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 very drought resistant[
] - this species is said to be the most drought tolerant member of the genus[
The leaves are remarkably variable in shape, ranging from ovate to being cut back to the midrib into three to seven narrow, linear lobes which are finely toothed [
Trees are used in the re-afforestation of arid areas[
Fruit - raw or cooked[
]. Very tart and sticky[
]. The pear-shaped fruit is about 30mm in diameter[
An extremely drought-resistant pear which may be widely used for the afforestation of arid regions with poor soils, where it can succeed on dry, stony slopes[
Of interest as a drought-resistant rootstock in grafting[
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.