Prunus x sultana

Voss.

Rosaceae Edible: Fruit, Seeds Potential hazards — see below

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Summary

A deciduous tree. Hardy to UK zone 6. Hermaphroditic flowers pollinated by insects. Tolerates light sandy, medium loamy, and heavy clay soils with good drainage. Grows in mildly acidic, neutral, or basic soils. Adapts to semi-shade or full sun and prefers consistently moist conditions.

Description

Edible Uses

The fruit can be eaten raw or cooked. It is large with a maroon skin and yellow flesh, and contains a single large seed. The seed is also edible raw or cooked, but should not be eaten if it tastes too bitter — see toxicity notes.

Medicinal Uses

No specific research has been recorded for this species, but all members of the genus contain amygdalin and prunasin, compounds that break down in water to release hydrocyanic acid (prussic acid or cyanide). In small amounts this highly poisonous substance can stimulate respiration, aid digestion, and produce a sense of well-being.

Known Hazards

Bitter almonds contain some 40 times the trace levels of cyanide found in sweet almonds. Extract of bitter almond was once used medicinally, but even in small doses, its effects are severe or lethal, especially in children; the cyanide must be removed before consumption. The acute oral lethal dose of cyanide for adult humans is reported to be 0.5–3.5 mg/kg (0.2–1.6 mg/lb) of body weight (approximately 50 bitter almonds), so that for children consuming 5–10 bitter almonds may be fatal. Symptoms of eating such almonds include vertigo and other typical cyanide poisoning effects. Almonds may cause allergy or intolerance. Cross-reactivity is common with peach allergens (lipid transfer proteins) and tree nut allergens. Symptoms range from local signs and symptoms (e.g., oral allergy syndrome, contact urticaria) to systemic signs and symptoms including anaphylaxis (e.g., urticaria, angioedema, gastrointestinal and respiratory symptoms). Almonds are susceptible to aflatoxin-producing moulds. Aflatoxins are potent carcinogenic chemicals produced by moulds such as Aspergillus flavus and Aspergillus parasiticus. The mould contamination may occur from soil, previously infested almonds, and almond pests such as navel-orange worm. High levels of mould growth typically appear as grey to black filament-like growth. It is unsafe to eat mould-infected tree nuts. Some countries have strict limits on allowable levels of aflatoxin contamination of almonds and require adequate testing before the nuts can be marketed to their citizens. The European Union, for example, introduced a requirement since 2007 that all almond shipments to the EU be tested for aflatoxin. If aflatoxin does not meet the strict safety regulations, either the entire consignment must be reprocessed to eliminate the aflatoxin or it must be destroyed.

Distribution

It is a temperate plant.

Where It Grows

This name is unplaced.

Cultivation

Thrives in a well-drained moisture-retentive loamy soil. Prefers some lime in the soil but is likely to become chlorotic if too much lime is present. Succeeds in sun or partial shade though it fruits better in a sunny position. There are some named forms selected for their ornamental value. Most members of this genus are shallow-rooted and will produce suckers if the roots are damaged. Plants in this genus are notably susceptible to honey fungus.

Propagation

Seed requires 2–3 months of cold stratification and is best sown in a cold frame as soon as it is ripe. Stored seed should be sown in a cold frame as early in the year as possible. Protect seed from mice. Germination can be slow, sometimes taking up to 18 months. Prick seedlings into individual pots when large enough to handle, overwinter in a greenhouse or cold frame, then plant out in late spring or early summer the following year. Being a hybrid, it will not breed true from seed. Cuttings of half-ripe wood with a heel can be taken in July/August in a frame. Softwood cuttings from vigorous plants can be taken in spring to early summer in a frame. Layering can also be done in spring.