Common Name: California Buckthorn

General Information

Frangula californica is a rounded to spreading shrub or small tree that can grow from 0.5 - 5 metres tall. A very variable plant, growth habit can range from a low, spreading shrub to an upright tree-like form, The leaves are usually persistent, but occasionally are deciduous[, ].
The plant is harvested from the wild for local use as a food and a medicine, It can be used in soil stabilization projects and is also grown as an ornamental, where it can be used as a hedge.
The plant is considered to be an invasive weed in Hawaii, where it has escaped from cultivation and become naturalized[].

Known Hazards

Species in this genus contain hydroxyanthracene derivatives which have a stimulant laxative effect upon the body, and many species are used traditionally as laxatives. In small doses, and for short periods, these can be safe and effective, but used over long periods they can weaken the body's natural ability to defecate and can have a range of long-lasting negative effects upon the body, including anaemia, malabsorption, haematuria and weight loss. Large single doses can cause severe purging.

Botanical References

,

Range

Western N. America - Oregon, California, Nevada, Arizona, New Mexico, Baja Norte

Habitat

Coastal sage scrub, desert scrub, chaparral, woodlands, forest edges, growing on dry, sandy or rocky slopes in ravines and on hillsides; at elevations up to 2,800 metres[].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	3.50 m
Pollinators	Insects
Cultivation Status	Ornamental, Wild

Cultivation Details

Frangula californica is a moderately cold-hardy plant, able to tolerate short periods with temperatures down to around -15°c when fully dormant. It grows best in areas with hot summers. In areas with cooler summers (even if the winters are mild), such as the maritime regions of the temperate zone, it often grows poorly, failing to properly ripen its wood and suffering frost damage over the winter[, ].
Grows well in full sun, succeeding also in light shade and doing well in the understorey of light woodland[]. Tolerant of a range of soils from sands to clays[]. Established plants are drought tolerant[]. Tolerant of occasional inundation of the soil[].
Plants usually commence flowering when around 3 - 5 years old from seed[]. Lifespan is believed to be in the region 100 - 200 years[].
Plants respond well to pruning and can be coppiced[].
Frangula californica is a very variable species, the Flora of N. America recognizes six subspecies that are more or less separated geographically, though intermediate forms do exist[].
The plant is reported to be a secondary host for the rust disease of velvet grass (Puccinia spp. or Holcus spp.)[].

Edible Uses

Fruit[]. A sweet flavour[, ]. The black, globose or slightly elongate fruit is around 10 - 15mm in diameter, containing 2 - 3 seeds[].

Medicinal

The bark has a laxative action and has been used in the treatment of constipation[, ]. It has strong purgative properties[]. The bark is also used as a kidney remedy and to treat influenza[].

A decoction of the leaves is used as a wash to treat dermatitis caused by contact with poison oak and poison ivy (Toxicodendron species). The leaves can be rubbud onto affected areas in the treatment of rheumatism or to heal infected sores and wounds[].

A piece of heated root, placed in the mouth, has been used as a treatment for toothache[].

Extracts of the plant have shown antimicrobial activity[].

Agroforestry Uses:

Within its native range, Frangula californica is a useful plant for erosion control on dry steep hillsides. Whilst it is best established from transplants, the plant's copious seed production, which is distributed by birds, can ultimately result in formation of good stands. Once established the plants show continuous vegetative regeneration from established root crowns. Regeneration also occurs after fire[, ].
The plant can be used as an informal hedge and also responds well to trimming[].

Other Uses

None known

Propagation

Seed - best sown in the autumn in a cold frame. Stored seed will require 1 - 2 months cold stratification at about 5° and should be sown as early in the year as possible in a cold frame or outdoor seedbed[]. Germination is usually good, at least 80% by late spring. Prick out the seedlings into individual pots when they are large enough to handle, and grow them on in the greenhouse or cold frame for their first winter. Plant them out in late spring or early summer of the following year.
Cuttings of half-ripe wood, mid summer in a frame[].
Cuttings of mature wood of the current year's growth, autumn in a frame.
Layering in early spring[].