Gaultheria shallon

Synonyms: salal, Brossaea shallon (Pursh) Kuntze (1891), Gaultheria fruticosa Menzies (1828), Shallonium serrulatum Raf. (1818)

Gaultheria shallon (Gaultheria shallon Pursh) – a species of the genus Gaultheria in the family Ericaceae. The name was given by the Swedish (Finnish) naturalist Pehr Kalm in honor of his friend from Quebec, Jean-François Gauthier – the first explorer of Canada's flora. It was first described in 1813 by the German botanist Frederick Traugott Pursh in the book "Flora Americae Septentrionalis". The first plant was discovered by the traveler Archibald Menzies.

Its native range is the northwestern part of North America, where it makes up a major part of the understory in coniferous forests. The plant has been introduced to Europe and in some countries has become an invasive species (because it spreads well by root suckers). It grows in forests and woodlands, preferring moist rocky or sandy soils, often on coastal cliffs; in some areas it extends into mountains up to 1300 m. It tolerates poorly temperatures down to about −20 °C poorly, and also does not tolerate prolonged snow cover. It is an indicator plant of cool maritime mesothermal climates and acidic, nitrogen-poor soils.

It is an evergreen shrub or subshrub 60–200 (rarely 500) cm tall. It grows slowly, under favorable conditions up to 20 cm per year. Stems are sturdy, with fissured reddish-brown bark, often stiffly hairy; young shoots are green, glandular-pubescent. Underground shoots (stolons) are very developed; in 1994 a rhizome 218 m long with 292 separate stems covering an area of 29 m² was excavated.

Leaves alternate, leathery, oblong-ovate, less often oval to nearly rounded, usually 3–10 cm long. The leaf apex is usually slightly acute, the base rounded or cordate, margin finely serrate. The upper surface is dark green, glabrous and glossy, the underside paler with distinct veins, sometimes slightly hairy. Mean leaf lifespan is 2–4 years.

Flowers hermaphroditic, grouped 5–15 in leaf axils or at branch tips in one-sided pendant racemes 7–15 cm long, the axes glandular-pubescent, pinkish-red. Pedicels white. Bracts colored, hairy. Calyx glandular-pubescent, reddish, the limb longer than the tube, divided into triangular-lanceolate lobes. After the flower fades the calyx does not fall off but enlarges, forming a berry-like structure around the true fruit. Corolla glandular-pubescent, white or pale pink, urn-shaped, shallowly divided into 5 reflexed lobes, 8.5–12.5 mm long. Stamens 10, hairy, dilated downward and adnate to the base of the corolla tube. Anthers two-celled (dithecal), with the characteristic ericaceous pores through which pollen is released. Ovary 5-loculed and 5-ribbed (rarely four-parted), situated on a 10-lobed disk, with numerous ovules. Pistil with a cylindrical style and an entire capitate or obtuse stigma. Pollination is carried out by bees, flies and hummingbirds, or by self-pollination. Begins flowering from about 4 years of age, from March (May) to July.

Fruits are 5-locular capsules surrounded by a fleshy expanding calyx that colors reddish, lilac or blackish-blue, covered with fine pubescence, globose, 6–10 mm in diameter. Seeds numerous (20–80 or more per capsule), smooth or reticulate, brown, up to 1 mm in diameter. Fruits ripen from late July through September–October and persist on the plants until the following spring. Seeds are dispersed by frugivorous birds and mammals. It has been shown that seeds that have passed through an animal’s digestive tract (for example, a bear’s) germinate better than those simply released from the capsules. In natural conditions, especially under a dense canopy, the proportion of germinating seeds is small; the plant is adapted to vegetative reproduction by long-lived underground stolons.

Hybrids: Gaultheria ×wisleyensis Marchant ex D.J.Middleton

Hardiness zone: 5 (-23°C).

Location: prefers moderately acidic soils (pH 5.5–6.5), although it can grow on very acidic soils. Good drainage is required, as it does not tolerate waterlogging. Mature plants are drought-tolerant; unestablished plants require regular watering during summer months. Does not tolerate prolonged direct sunlight, best planted in partial shade.

Planting: carried out in spring. Fill the planting hole with peat or humus, coarse sand and conifer litter in a ratio of 2:1:3. On heavy clay or poor soils it is advisable to remove the top layer and fill the planting hole with a suitable mix. If the subsoil is alkaline, proceed similarly and regularly water the plant with acidified water to maintain optimal acidity. For this, dissolve 1 tsp citric or oxalic acid in 3 L of water or 1 tbsp 9% vinegar in 10 L of water.

Care: during dry periods moderate watering and foliar spraying are recommended.

Fertilization: apply in spring a complete mineral fertilizer for rhododendrons (20–30 g/m²)

Pruning: prune old dry branches in spring.

Propagation: the easiest method is by rhizome. By digging around mature bushes, cut off underground shoots with roots and aboveground shoots. Then divide the rhizome into as many divisions as possible with a young shoot or bud and roots. Plant them into a bed filled with acidic peat (or directly into pots). Take cuttings in June. Remove leaves from the lower part of the cutting (length 5–6 cm). Plant into a bed in a plastic-covered greenhouse. Roots form in 4–5 weeks. In August remove the greenhouse cover. Leave the plants to overwinter in the bed, first mulching it with peat and covering with spunbond. The next year they can be planted to a permanent site or potted for further growing. They can also be propagated by seed. After overwintering in the open ground seeds have already undergone stratification and can be sown immediately. Dry seeds need stratification for 3 months. It is best to mix them with moist moss, place in a glass jar, close the lid tightly and put in a refrigerator or under the freezer compartment at 2–4°C. Then sow the seeds in containers filled with Sphagnum peat, not covering them with soil. Seedlings appear in 2–3 weeks. At the stage of 4–5 true leaves they are pricked out 1–2 per pot and grown on for 2–3 years. After that they can be planted in their permanent location.

Diseases and pests: little susceptible to pests and diseases.

Uses: Gaultheria shallon shrubs are planted together with heathers and conifers or placed in tubs and window boxes to add bright spots to a grey winter garden. Also used as a groundcover, in rock gardens and for bouquet decoration (the leaves retain shine and grey-green color for a long time). The fruits are edible.