Mahonia japonica and Mahonia bealei are very similar plants and have often been confused in horticulture. Many seedlings that have been raised from cultivated plants are hybrids between the two species[].
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:

General Information

Mahonia japonica is an evergreen shrub with stiff, stout, sparsely branched stems; it can grow around 100cm tall[].
The plant is harvested from the wild for local use as a medicine. This species is cultivated extensively as an ornamental in Japan and sporadically also in the warmer parts of Europe and the United States[].

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

E. Asia - southern China, Taiwan

Habitat

Damp woodlands in upland areas[, ]. Forests, thickets; at elevations from 800 - 3,400 metres[]. Not found in a truly wild situation, this species is possibly only a cultigen.

Properties

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

Cultivation Details

Mahonia japonica is a very cold tolerant plant. When fully dormant, it can tolerate temperatures down to about -20°c, though the young growth in spring is much more sensitive and can be damaged by temperatures around 0°c[].
An easily grown shrub, it thrives in any good garden soil[] including heavy clays. Prefers a semi-shaded woodland position in a damp, slightly acid to neutral humus-rich soil[]. Plants can succeed under very heavy tree shade[]. Succeeds in poor soils when the leaves will often become bright red, especially if the plant is in full sun.
Plants are very tolerant of pruning and can be cut right back into old wood if they have outgrown their welcome[].
This species is closely related to Mahonia bealei[, ]. It hybridizes freely with other members of the genus.
The flowers have a delicious perfume[]. The form 'Hiemalis' bears larger flower spikes which are almost as strongly scented as Lily of the Valley (Convallaria majalis)[].
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[]. We have no data on susceptibility for this species[].

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[]. The ovoid fruit is about 9mm long[], it ripens in spring and crops can be quite good if the plant is in a sheltered position[]. The fruit is produced in large clusters and so is easy to harvest[].

Medicinal

The leaf is febrifuge and is used as a tonic in cases of cancer[].

The seed is febrifuge and tonic[].

The roots and stems are antirheumatic, antitussive, depurative, expectorant and febrifuge[, ]. A decoction is used in the treatment of bone-breaking fevers, dizziness and tinnitus, sore eyes, ulcers, toothaches, backache, sore throats, weak knees, jaundice, tuberculosis, haemoptysis, diarrhoea, dysentery and enteritis[, ].
The root and root bark are best harvested in the autumn[].


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[].

Other Uses

None known

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.