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: Japanese Plum

General Information

Prunus japonica nakai is an evergreen shrub that can grow 100 - 150cm tall[].
The plant is harvested from the wild for local use as a food and a medicine. It is sometimes grown as an ornamental in gardens.

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

E. Asia - northern China, Korea

Habitat

Open country and roadsides[]. Sunny mountain slopes at elevations of 100 - 200 metres[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	1.00 m
Pollinators	Insects
Cultivation Status	Ornamental, Wild

Cultivation Details

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[, ].
A very ornamental plant[], but it is subject to die-back[]. Plants in this genus are notably susceptible to honey fungus[].
This sub-species has larger plum-like fruits up to 50mm in diameter[].
Closely related to Prunus glandulosa[, ].
Most members of this genus are shallow-rooted and will produce suckers if the roots are damaged[].

Edible Uses

Fruit - raw or cooked. A sweet agreeable flavour, they make a good pie[]. A very good size, it can be up to 50mm in diameter with one large seed[].

Seed - raw or cooked. Do not eat the seed if it is too bitter - see the notes above on toxicity.

Medicinal

The kernels are aperient, carminative, demulcent, deobstruent, diuretic, lenitive and ophthalmic[, , , , ]. Their use lowers the blood pressure[]. A decoction is used in the treatment of sluggish colon, constipation, oedema and inadequate elimination of urine[].
The pits of this sub-species are aphrodisiac for both sexes[].
The root is used in the treatment of constipation, children's fever, pinworms and teeth ailments[].
All members of the genus contain amygdalin and prunasin, substances which break down in water to form hydrocyanic acid (cyanide or prussic acid). In small amounts this exceedingly poisonous compound stimulates respiration, improves digestion and gives a sense of well-being[].

Other Uses

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

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[, ].
Softwood cuttings from strongly growing plants in spring to early summer in a frame[].
Layering in spring.