Gaultheria shallon
(salal)

Preferred Common Name

• salal

Other Scientific Names

• Brossaea shallon (Pursh) Kuntze
• Shallonium serrulatum Raf.

International Common Names

• English: shallon

Local Common Names

• Germany: shallon-rebhuhnbeere; shallon-scheinbeere

EPPO code

• GAHSH (Gaultheria shallon)

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Ericales
•                         Family: Ericaceae
•                             Genus: Gaultheria
•                                 Species: Gaultheria shallon

The genus Gaultheria was first created by the German American botanist Pehr Kalm in his “Guide of Canada”, in homage to the French Canadian botanist Jean Françoise Gaultier.

The names shallon and salal are of Amerindian origin, probably from the Chinook language sallal, recorded during Lewis and Clack expedition as shelwel, shellwell (Oxford Dictionary, 2014).

G. shallon is a perennial, evergreen shrub with a growth form from sprawling to erect. G. shallon can reach 0.2-5 m tall, growing strongly from rhizomes. Leaves are evergreen, alternate, round to ovate, pointed, glossy green, with a leathery texture. The lower side of the leaf is rough and lighter green. Each leaf has a base rounded or cordate, margins finely serrulate (with the “teeth” fimbriate apically), apex mucronate/apiculate or aristate, surfaces glabrous, reaching 5-10 cm long (Flora of North America Editorial Committee, 2015). Young shoots are red. Mature bark and twigs of G. shallon are grayish-brown and smooth. The twigs change angles between each node, giving it a zigzag appearance. The flowers are hermaphroditic (have both male and female organs) and are pollinated by insects. The inflorescence consists of a bracteate raceme, one-sided, with 5 to 15 flowers at the ends of branches. Flowers are white to pale pink, urn-shaped and they appear in late spring and early summer. Each flower is composed of a deeply five-parted, glandular-haired calyx and an urn-shaped pink to white, glandular to hairy, five-lobed corolla, 7-10 mm long. Flowers mature to fleshy, reddish to blue, rough-surfaced, hairy, nearly spherical fruit 6-10 mm in diameter (Pojar and MacKinnon, 2004).

G. shallon was introduced to Britain from North America in 1828 by David Douglas, who intended the plant to be used as an ornamental (Pojar and Mackinnon, 2004). By 1914 it could be seen growing in the wild. After establishing in heathlands as a mild invasive species, its spread was traditionally controlled by cattle ranchers. Probably as a result of these practices and in view of its potential as forage, G. shallon was introduced into Ireland in 1961 (EPPO, 2014).

Further introductions in Europe are likely to be associated with releases from botanical gardens or collectors. In New Zealand is believed that G. shallon has been naturalized since 1946 (Webb et al., 1988). It was introduced into Tasmania, Australia in 1973 where it has also naturalized (Council of Heads of Australaisan Herbaria, 2014).

Soil drainage

• free
• seasonally waterlogged

Soil reaction

• acid
• neutral

Soil texture

• light
• medium

Special soil tolerances

• infertile
• shallow

Natural Dispersal

G. shallon is naturally dispersed over short distances through the production of rhizomes.

Vector Transmission

The berries are attractive to birds and are consumed and excreted into new areas facilitating its spread.

Intentional Introduction

G. shallon was introduced into the British Isles as forage and cattle cover in the early nineteenth century and again in mid twentieth century. It was also planted for game cover in woods and on heaths. It was also introduced into botanical gardens for ornamental purposes where it has since escaped.

Impact on Habitats

G. shallon is a strong competitor for nutrients. In nutrient poor sites it can outcompete trees or other shrubs by being the first species to reach and use the available nutrients (especially nitrogen), reducing other species growth (Prescott et al., 2003; Prescott and Sajedi, 2008). G. shallon can also influence the mineralization of nitrogen through the release of tannins (Prescott et al., 1996).

Impact on Biodiversity

G. shallon can form dense thickets through the development of suckers from roots and rhizomes. As a result, G. shallon can rapidly take over large areas as the thickets can shade out any vegetation underneath and provide very little growing space for other species. This can decrease plant diversity in particular that of shade intolerant species.

• Invasive in its native range
• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Tolerant of shade
• Highly mobile locally
• Long lived
• Has high reproductive potential
• Has propagules that can remain viable for more than one year
• Reproduces asexually

• Conflict
• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Modification of nutrient regime
• Negatively impacts agriculture
• Negatively impacts forestry
• Reduced native biodiversity

• Allelopathic
• Competition - monopolizing resources
• Competition - shading
• Competition - smothering

• Highly likely to be transported internationally deliberately

Economic Value

In the Pacific Northwest, G. shallon is the heart of a local but important industry of cut flowers and therefore has some economic value. Wild G. shallon boughs are harvested and used as a floral green in floral arrangements (Ballard and Huntsinger, 2006).

Social Benefit

G. shallon berries were a large component of traditional North American diets due to their abundance and ease of harvest. Several tribes have used the berries as part of feasts, mixed with salmon eggs and the leaves as hunger suppressant (Pojar and MacKinnon, 2004). G. shallon can be sustainably harvested for a large number of years before the growth of the plant is reduced, as it is frugal in nutrient needs and regenerates quickly. G. shallon berries taste similar to, the bilberries (Vaccinium myrtillus), another member of the Ericaceae family. Fruits can be eaten raw, cooked or dried for later use (Grieve, 1971; Hedrick, 1972; Simmons, 1972; Facciola, 1998; Pojar and Mackinnon, 2004). Dried fruits are used as sweeteners and in jams, preservatives, or drinks (Facciola, 1998). The leaves can be used for making tea (Turner, 1979). Several traditional and natural dyes have been created from G. shallon. From the berries it is possible to obtain a dark purple dye and green-yellow dye from the infusion of the leaves (Moerman and Eierman, 1998). 

In traditional medicine, G. shallon has been used as an astringent, a poultice and a stomach tonic. The poultice consists of a mixture of the toasted, pulverized leaves. The plaster can be applied to cuts and insect bites and leaves can be chewed and applied to burns and sores. The stomach tonic is made from an infusion of the leaves and helps to reduce internal inflammation such as stomach ulcers, heart burn, treat diarrhea, period pain, coughs and tuberculosis (Moerman and Eierman, 1998).

Environmental Services

Environmental services within forest and wetland ecosystems provided by G. shallon in its native range include supporting services such as primary production, nutrient recycling and soil formation, regulating services such as carbon sequestration, erosion control and soil stability and hydrological stabilization. Mammals which may use the berries as food include the red squirrel (Sciurus vulgaris), Townsend's chipmunk (Neotamias townsendii), Douglas' squirrel (Tamiasciurus douglasii) and the black bear (Ursus americanus). In the UK cattle will also feed on the berries. In its native range the fruit are a good food source for birds such as the blue grouse (Dendragapus species) and the band-tailed pigeon (Patagioenas fasciata). In addition to this, in both its native and introduced range many species of songbirds feed on the fruit when available. Hummingbirds may also feed on the flowers.

G. shallon is also an important plant in gardening, especially in its native range and in many parts of North America. It is often used as a ground cover plant for a shady position under trees which spreads slowly by means of suckers (Brickell, 2010). G. shallon may also be used to make green fences for which seedlings should be spaced about 90 cm apart each way (Thomas, 1970). The reason for this is that G. shallon can grow very rapidly and densely. G. shallon is often used to “deer-proof” gardens as the foliage is very dense and usuaally not favored by deer. However, other thicket forming species may better serve in this role as reports exist of mule deer (Odocoileus hemionus), black-tailed deer (O. hemionus columbianus) elk (Cervus canadensis) and small mammals such as beaver (Castor species) feeding on foliage.