The taxonomic history of Prunus is long and complicated, in part due to the economic value of its fruit crops and also the ease with which some species hybridize. Here, Prunus is circumscribed in its broad sense based on the argument that when viewed on a worldwide scale, the morphologic discontinuities among the segregate genera diminish and they overlap with one another. Included here are species that have at times been placed in the genera Amygdalus, Armeniaca, Cerasus, Laurocerasus, Padus, and Persica.
At the species level, Prunus has been the object of the usual combining and splitting common among taxonomists with different philosophies and opinions. In particular, over-reliance on the indument of various vegetative and floral parts has led to the naming of numerous species and infraspecific taxa. Similarly, too much has been made of fruit colour and palatability in naming taxa of Prunus. It is very likely that, as molecular and genetic data are analyzed and, more importantly, correlated with morphological data, circumscriptions will be redrawn and the number of Prunus species will be reduced[].

Common Name: Almond

General Information

Prunus dulcis is a deciduous shrub or a small tree with erect branches when young, becoming horizontally-spreading as it grows older; it can grow 4 - 8 metres tall[, , , ].
The almond is one of the most commonly consumed nuts on Earth. It is often cultivated in warmer regions of the temperate zone, especially in the United States, which now dominates world almond production with over 40% of the annual crop, all of it grown in or near the Central Valley of California.

Known Hazards

The plant (especially the seed and young shoots) contains cyanogenic glycosides, especially amygdalin and prunasin. 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 fruits and flowers of most members of this genus generally have low or very low concentrations of this toxin, though the seeds and young shoots can contain much higher levels.
The levels of toxin can be detected by the level of bitterness:- for example sweet tasting almond seeds are a major food crop and are often eaten in quantity, whilst bitter tasting almond seeds are used as a flavouring (in marzipan for example) but are not usually eaten on their own.
In general, it can be considered safe to eat any fruit or seed from species in this genus that either have a sweet flavour or are slightly bitter. Great caution should be taken, however, if the flavour is moderately to very bitter[].

Botanical References

, ,

Range

Europe - E. Mediterranean to C. Asia.

Habitat

Cultivated ground, thickets, hedges, rocky places near cultivation[]. Mountainous areas, favouring sunny slopes, woody shrubby formations, often forming rather large underbrush, in stony and fine earth rubble; at elevations from 800 - 1,600 metres[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	6.00 m
Pollinators	Insects
Self-fertile	Yes
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

The almond prefers a Mediterranean or a Continental climate, with a clear distinction between winter and spring, in milder maritime areas it can be induced into flower too early in the season and is then very liable to be damaged by frosts[].
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[, ].
The almond is often cultivated in the temperate zone for its edible seeds, there are many named varieties[, ].
The United States now dominates world almond production with over 40% of the annual crop, all of it grown in or near the Central Valley of California. The in-shell 'nuts' sold in stores are the pits of drupes with the leathery mesocarp removed[].
There are two basic forms of almonds, one with bitter seeds and one with 'sweet' seeds. The bitterness is caused by the presence of cyanogenic glycosides (see notes above). Although the bitter forms are used in making marzipan and as a food flavouring, the seeds themselves should not be eaten in anything other than small quantities. Even the sweet forms should not be eaten in very large quantities. (Approximately 900 of the sweet seeds at one time is considered to be a toxic dose for the average adult).
Trees are hardier when grown on a plum rootstock[]. Almond seedlings are the preferred rootstock when plants are grown on hot dry soils, peach rootstocks are better for heavier soils[].
Almond is among the earliest blossoming trees and one of the first signs of spring in areas where it is grown[].
There is likely to be a shortage of pollinating insects around when the tree is in flower so hand pollination may improve the crop.
Although partially self-fertile, better crops are obtained if at least 2 different cultivars are grown[].
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[].

Edible Uses

Seed - raw, cooked or dried and ground into a powder for use in confections etc[, ]. The whole seed can also be roasted, sprouted or used in cakes, confectionery and pastry[]. The sweet-flavoured forms have a delicious flavour but bitter forms should not be eaten in any quantity - see the notes above on toxicity. The seed is somewhat difficult to digest and so needs to be thoroughly masticated[]. It can be blended with water to make almond milk[].
The seed with its shell is around 27 - 34mm long, (14 - 26mm wide, 8 - 16,m thick[].

The seed contains up to 45% of an edible oil[, ]. It is used mainly as a food flavouring and in cooking[, ]. The oil has a high content of mono-unsaturated fatty acids, and is usable for many purposes[].

An edible gum is obtained from points of damage on the stems[].

Medicinal

As well as being a tasty addition to the diet, almonds are also beneficial to the overall health of the body, being used especially in the treatment of kidney stones, gallstones and constipation[]. Externally, the oil is applied to dry skins and is also often used as a carrier oil in aromatherapy[, ]. The seed is demulcent, emollient, laxative, nutritive and pectoral[, , ]. When used medicinally, the fixed oil from the seed is normally employed4].
The seed contains 'laetrile', a substance that has also been called vitamin B17[]. This has been claimed to have a positive effect in the treatment of cancer, but there does not at present seem to be much evidence to support this[]. The pure substance is almost harmless, but on hydrolysis it yields hydrocyanic acid, a very rapidly acting poison - it should thus be treated with caution[]. In small amounts this exceedingly poisonous compound is used medicinally since it stimulates respiration, improves digestion and gives a sense of well-being[].

The leaves are used in the treatment of diabetes[].

The plant contains the antitumour compound taxifolin[].

Other Uses

An oil expressed from the seeds is an excellent lubricant in delicate mechanisms such as watches[]. It is often used in soaps and cosmetics because it has a softening effect on the skin[, ].

A green dye can be obtained from the leaves[].
A dark grey to green dye can be obtained from the fruit[].
A yellow dye is obtained from the roots and leaves[].

The bruised leaves, when rubbed within any container, will remove strong odours such as garlic or cloves so long as any grease has first been fully cleaned off[].

A gum from the stems is used as an adhesive[].

The burnt shell yields a valuable absorbent for coal gas[].

The burnt pericarp is rich in potassium, it is used in soap making[].

The seed contains amygdallin, under the influence of water and in the presence of emulsion it can be hydrolized to produce benzaldehyde (the almond aroma, formula C6 H5 CHO) and prussic acid (the toxic principle)[].

The light brown wood is close and even-grained, moderately hard[].

Propagation

Seed - requires 2 - 3 months cold stratification and is best sown in a cold frame as soon as it is ripe[]. Sow stored seed in a cold frame as early in the year as possible[]. Protect the seed from mice etc. The seed can be rather slow, sometimes taking 18 months to germinate[]. Prick out the seedlings into individual pots when they are large enough to handle. Grow them on in a greenhouse or cold frame for their first winter and plant them out in late spring or early summer of the following year.
Cuttings of half-ripe wood with a heel, mid summer in a frame[, ]. Difficult.
Softwood cuttings from strongly growing plants in spring to early summer in a frame[].
Cuttings of mature wood, late autumn in a frame.
Layering in spring.