Prunus nigra

Prunus nigra, the Canada plum, Canadian plum, or black plum, is a species of Prunus native to eastern North America.

Description

A very small tree. It grows up to 9 m tall. The trunk can be 25 cm across. The trunk is short and crooked and often divided into several branches. The leaves are broadly oval and 6-12 cm long. They have a long slender tip. The base is wedge shaped. There are rounded teeth along the edge. The flowers are white but turn pink. They are 15-25 mm across. They occur in small clusters. The fruit are 25-30 mm long. The skin is thick and red. The flesh is yellow and juicy and sour.

Edible Uses

The fruit can be eaten raw or cooked — fresh out of hand, in pies and preserves, or dried for later use. It is small, about 3cm in diameter, with a sour flavour and thick skin, and is not particularly palatable; however, the flavour improves considerably after the fruit has been touched by a few frosts. It contains one large seed. The seed contains prussic acid, and cases of children dying after eating the fruit without removing the stones have been recorded.

Traditional Uses

The fruit are eaten raw. They are also used in preserves. They are stewed and used in jelly, pies, sauces, fruit juices, marmalade and plum butter. They are dried and used like raisins.

Medicinal Uses

An infusion of the inner bark has been used to treat colds. An infusion of the bark has also been used to settle the stomach when it will not retain food. As with all members of the genus, the plant contains amygdalin and prunasin, which break down in water to form hydrocyanic acid (prussic acid). In small amounts this highly poisonous compound stimulates respiration, improves digestion, and produces a sense of well-being.

Known Hazards

Although no specific mention has been seen for this species, it belongs to a genus where most, if not all members of the genus produce hydrogen cyanide, a poison that gives almonds their characteristic flavour. This toxin is found mainly in the leaves and seed and is readily detected by its bitter taste. It is usually present in too small a quantity to do any harm but any very bitter seed or fruit should not be eaten. In small quantities, hydrogen cyanide has been shown to stimulate respiration and improve digestion, it is also claimed to be of benefit in the treatment of cancer. In excess, however, it can cause respiratory failure and even death.

Distribution

Temperate. It grows best in river valleys. It is often on lime soils.

Where It Grows

Argentina, Australia, Canada, North America, South America, USA,

Cultivation

Thrives in a well-drained moisture-retentive loamy soil, growing well on limestone. 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. Sometimes cultivated as a fruit tree in Canada and America, there are some named varieties that have been selected for their edible fruit. This species is closely related to P. americana. A bad companion for potatoes, the plum tree harbours aphids that can damage the potatoes. 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. Prunus americana var. nigra (Aiton) Waugh is a synonym of Prunus nigra Aiton. It may also be recorded as Prunus americana nigra. A sprouting standard sending up shoots from the base.

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, with protection from mice. Germination can be slow, sometimes taking 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. Half-ripe cuttings with a heel can be taken in July/August in a frame; softwood cuttings from vigorous plants in spring to early summer in a frame. Layering in spring is also an option.

Other Uses

A green dye can be obtained from the leaves, and a dark grey to green dye from the fruit. The inner bark has been used as an astringent colour fixative when dyeing with other plants. The wood is hard, moderately heavy, and close-grained, weighing 43lb per cubic foot, but the tree is too small to be used commercially.

Other Information

Fruit are sold in markets. It is cultivated.

Notes

There are about 200 Prunus species. Prunus nigra Desf. is a synonym of Armeniaca dasycarpa (Ehrh.) Borkh..

Synonyms

References (18)

• Beckstrom-Sternberg, Stephen M., and James A. Duke. "The Foodplant Database." http://probe.nalusda.gov:8300/cgi-bin/browse/foodplantdb.(ACEDB version 4.0 - data version July 1994)
• Facciola, S., 1998, Cornucopia 2: a Source Book of Edible Plants. Kampong Publications, p 203
• Farrar, J.L., 1995, Trees of the Northern United States and Canada. Iowa State University press/Ames p 384
• Fisk, J. R. & Hoover, E., 2015, Wild Fruits of Minnesota. A Field Guide. University of Minnesota p 28
• Grandtner, M. M., 2008, World Dictionary of Trees. Wood and Forest Science Department. Laval University, Quebec, Qc Canada. (Internet database http://www.wdt.qc.ca)

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