This species is closely related to Mahonia haematocarpa, differing mainly in having broadly ovate bracts up to 8mm long[]. It is also closely related to Mahonia nevinii[].
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: Texas Mahonia

General Information

Mahonia swaseyi is an evergreen shrub growing 100 - 200cm tall. Suckering from the base, the plant forms a dense cluster of stems with elongate primary and short or somewhat elongate axillary shoots[].
The plant is harvested from the wild for local use as a food and a medicine. It has been recommended as a potential fruit crop]183].

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

Southern N. America - Texas (Edwards Plateau)

Habitat

Besides rocky streams in Texas. Limestone ridges and canyons; at elevations from 150 - 600 metres[].

Properties

Edibility Rating
Medicinal Rating
Habit	Evergreen Shrub
Height	2.50 m
Pollinators	Bees
Cultivation Status	Wild

Cultivation Details

Mahonia swaseyi is native to the semi-arid, warm temperate zone in southern N. America and is not hardy in the colder areas of the temperate zone. It can tolerate occasional temperatures down to between -5 and -10°c[].
Unlike most members of the genus, this species requires a dry, perfectly drained position in full sun, a gritty slightly acid soil is best[]. It does well in a hot, dry position[] and grows best on a sunny south facing wall[]. It requires as sunny a position as possible[, ].
This plant has been recommended for improvement by selection and breeding as an edible fruit[].
Hybridizes in the wild with Mahonia trifoliolata[].
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 susceptible to infection by the fungus[].

Edible Uses

Fruit - raw but more usually cooked in preserves[]. Pleasantly acid, it can also be dried and used as raisins[]. Unfortunately, there is relatively little flesh and a lot of seeds[]. The fruit, which can be dry or juicy, is up to 15mm in diameter[, ].

The roasted seed is a coffee substitute[].

Medicinal

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 greenhouse[]. 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 the greenhouse for at least their first winter. Plant them out in late spring or early summer and consider giving them some protection from the cold for their next winter.
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.