The genus Mahonia is not universally accepted. Many botanists prefer to treat it as part of Berberis - as per the Flora of N. America[]. However, although they are very closely related (and there are some intergeneric hybrids), from the point of view of the gardener they are quite distinct genera. We are therefore following the treatment in the Flora of China[] which treats them as distinct. There is, however, at least one major revision (of the Chinese genera) currently (2016) in preparation and we will review the position of Mahonia once we have seen that revision[].

Common Name: Oregon Grape

General Information

Mahonia nervosa is an evergreen shrub usually growing 10 - 80cm tall, occasionally reaching 200cm. Suckering from the base, the plant spreads to form a loose clump of several stems[]..
The plant is harvested from the wild for local use as a food and a medicine. It is sometimes grown as an ornamental, where it can be used to provide ground cover in shady situations.

Known Hazards

All parts of the plant contain the alkaloid berberine - this is most concentrated in the roots, stems and inner bark, and least concentrated in the fruits. In small quantities berberine has a range of effective medicinal applications but, in excess, can cause vomiting, lowered blood pressure, reduced heart rate, lethargy, and other ill-effects.
The fruit of most, if not all, members of this genus are more or less edible and can be eaten in quantity since the levels of berberine in the fruit are very low.

Botanical References

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Range

Western N. America - southern British Colombia, Washington, Oregon, California.

Habitat

Light dry woods and rocky ledges[, ]. Open or shaded woods, often in rocky areas; at elevations up to 1,800 metres[].

Properties

Edibility Rating
Medicinal Rating
Habit	Evergreen Shrub
Height	0.50 m
Growth Rate	Slow
Pollinators	Insects
Cultivation Status	Ornamental, Wild

Cultivation Details

An easily grown plant, it thrives in any good garden soil[, ] but also succeeds in poor dry ones. Another report says that it is best on a lime-free soil[]. Grows well in heavy clay soils. Prefers a sunny position[] but succeeds in heavy woodland shade[].
Hybridizes freely with other members of this genus.
Plants are growing and fruiting well at Wakehurst Place in Sussex, but they do not generally do well in Britain[].
Resistant to honey fungus[].
Some Berberis/Mahonia species (especially Berberis vulgaris) harbour the black stem-rust fungus (Puccinia graminis Persoon). This is a major disease of wheat and barley crops and can spread from infected barberries to the grain crop. The sale or transport of susceptible or untested species of Berberis is illegal in the United States and Canada[]. This species is resistant to infection by the fungus[].

Edible Uses

Fruit - raw or cooked[, , ]. An acid flavour but it is rather nice raw, especially when added to muesli or porridge[]. Unfortunately, there is relatively little flesh and a lot of seeds[]. Too acid for most tastes but they are very good in jams, jellies, pies etc[]. They can also be used to enhance the flavour of bland fruits or made into a refreshing lemon-flavoured drink[]. The fruit is about 8mm in diameter[].

Young tender leaves - cooked. Simmered in a small amount of water and eaten as a snack[].

Medicinal

The root is alterative and tonic[]. It improves the digestion and absorption and is recommended in the treatment of psoriasis, syphilis and impure blood conditions[, ]. A decoction of the peeled and chopped root bark has been used as a wash in treating arthritis and as an eyewash for red itchy eyes[].

The fruit is an excellent safe and gentle laxative[].

This is one of several species closely related to the Oregon Grape (Mahonia aquifolium) and with very similar medicinal uses[]. These uses are:-

Oregon grape was often used by several native North American Indian tribes to treat loss of appetite and debility[]. It is still a popular remedy in modern herbalism, being used mainly in the treatment of gastritis and general digestive weakness, to stimulate liver, kidney and gallbladder function and to reduce catarrhal problems[, , ]. Extensive trials have shown that a cream containing the root or stem extract is a safe and effective treatment for psoriasis and other skin conditions.

The root and root bark are alterative, antibacterial, antioxidant, blood tonic, cholagogue, diuretic, laxative and tonic[, , , ]. It improves the digestion and absorption and is taken internally in the treatment of psoriasis, syphilis, haemorrhages, stomach complaints and impure blood conditions[, , ].
Externally, it is used in the form of a cream to treat skin conditions such as psoriasis, whilst a decoction has been used as a gargle for treating sore throats and as a wash for blurry or bloodshot eyes[].
The roots are harvested in late autumn or early spring and dried for later use[].

The fruit is an excellent gentle and safe laxative[].

In Germany, several studies have indicated that Mahonia aquifolium exerts anti-psoriasis activities though inhibiting antiinflammation and hyperproliferation of keratinocytes, and that alkaloids may be responsible for the anti-psoriasis activity of this plant[].
Mahonia species have a long history of medicinal usage, with several members of the genus being commonly used in traditional medicine and also in modern herbalism. They are employed in the treatment of a wide range of conditions and have, in particular, been demonstrated to exert good efficacy in the clinical treatment of dysentery, internal and external haemorrhage, acne vulgaris and chronic pharyngitis amongst other diseases. Phytochemical research into this genus has resulted in the identification of more than 150 chemical constituents, amongst which alkaloids are predominant. The isolated compounds and crude extracts have been shown to exhibit a wide spectrum of in vitro and in vivo pharmacological effects, including antimicrobial, anti-inflammatory, hepatoprotective, antioxidant, antimutagenic and analgesic properties[]
Berberine, an alkaloid that is universally present in the rhizomes and stems of Mahonia species, has been shown to have a marked antibacterial effect[] and is also used as a bitter tonic[]. Since it is not appreciably absorbed by the body, it can be used orally in the treatment of various enteric infections, especially bacterial dysentery[].
Berberine has also shown antitumour activity[].
The plant should not be used with Glycyrrhiza species (Liquorice) because this nullifies the effects of the berberine[].

Agroforestry Uses:

Plants can be grown as a ground cover, spaced about 30cm apart each way[]. They are very slow to spread[] and so will need weeding for their first few years after planting[].

Other Uses

A yellow dye is obtained from the inner bark of the stem and roots[, , ].
Dark green, violet and dark blue-purple dyes are obtained from the fruit[].
A green dye is obtained from the leaves[].

Propagation

Seed - best sown as soon as it is ripe in a cold frame[]. It usually germinates in the spring[]. 'Green' seed (harvested when the embryo has fully developed but before the seed case has dried) should be sown as soon as it is harvested and germinates within 6 weeks[]. Stored seed should be sown as soon as possible in late winter or spring. 3 weeks cold stratification will improve its germination, which should take place in 3 - 6 months at 10°c. Prick out the seedlings when they are large enough to handle and grow them on in a cold frame for at least their first winter. Plant them out in late spring or early summer.
Division of suckers in spring[]. Whilst they can be placed direct into their permanent positions, better results are achieved if they are potted up and placed in a frame until established[].
Leaf cuttings in the autumn.