Plant problems

Why Are My Salal Leaves Curling?

Q: What is salal used for in floristry?

Salal (Gaultheria shallon) is one of the most widely used decorative foliage plants in the florist trade worldwide, sold under the trade names 'salal,' 'lemon leaf,' or 'box leaf' (though it is not related to lemon or box). The glossy, dark green, leathery, rounded to oval leaves, 5 to 10 cm long, are harvested primarily from wild stands in the Pacific Northwest of North America (principally Oregon, Washington, and British Columbia) where salal grows in extensive dense thickets in coastal coniferous forests. The wild harvesting of salal has become a significant commercial industry in the Pacific Northwest, providing income for many rural communities; in Oregon alone, tens of millions of stems are harvested and exported each year. Salal stems last 2 to 3 weeks in a vase or arrangement; the leaves are popular as a filler in bouquets and wreaths because they hold their shape and colour without wilting. UK florists use salal extensively; it is sold in bunches at flower markets. Growing your own salal as a cutting garden plant in the UK is feasible in acidic, shaded conditions; the plant produces abundant stems that can be harvested for arrangements, though cultivated stems are less dense and vigorous than those harvested from wild Pacific Northwest thickets.

Q: How do I grow salal in the UK?

Salal (Gaultheria shallon) grows well in UK conditions where the soil is acidic and the site is shaded or partially shaded; its natural habitat (under a dense conifer canopy in a moist Pacific coast climate) has significant similarities to shaded UK woodland gardens and the acidic soils of Scotland, Wales, and western England. Plant in acidic soil (pH 4.5 to 6.0) enriched with ericaceous compost or leaf mould; avoid lime and alkaline conditions. Salal tolerates dry shade better than most ericaceous plants once established, which makes it useful under rhododendrons and conifers where the soil tends to be dry. It spreads by underground suckers into a dense thicket over time; in some UK conditions it can become invasive in the same way that laurel does, particularly on acidic soils in mild, moist western areas. Space plants 1 to 1.5 metres apart and be prepared to manage the spread. Salal produces attractive white to pink, urn-shaped flowers in late spring followed by dark purple-black berries in late summer; the berries are edible and were an important food for Pacific Northwest indigenous peoples, eaten fresh, dried, or mixed with other foods. In the UK, salal is available from specialist nurseries supplying woodland and ericaceous plants.

Salal (Gaultheria shallon) is an evergreen shrub from the Pacific Northwest of North America, widely grown in UK woodland gardens for its attractive, glossy dark green foliage and valued by florists worldwide as decorative "lemon leaf" or "box leaf" filler. A member of the Ericaceae family, it requires acidic soil and tolerates dry shade better than most ericaceous plants once established. Vine weevil root damage in containers and drought stress are the most common reasons for leaf curl in UK cultivation.

Vine weevil

Vine weevil (Otiorhynchus sulcatus) is the most damaging pest of salal in UK containers and pots. The diagnostic sign is characteristic rounded notches bitten from the leaf margins by adult weevils in summer; the more serious damage comes from the white, C-shaped larvae that feed on the roots through autumn and winter, causing the plant to show sudden wilting and leaf curl in spring when root damage becomes severe enough to prevent water uptake. Container-grown salal is most at risk because the root system is confined and cannot grow away from the larvae; established ground-planted salal with an extensive spreading root system is better able to tolerate moderate vine weevil pressure.

What to do

Apply nematodes (Steinernema kraussei) to moist compost in late August to October and again in March; highly effective at soil temperatures above 5°C. Check the compost for white C-shaped larvae when repotting; remove by hand. Place yellow sticky traps near the plants to capture adults. Do not leave containers sitting on bare soil in summer; adults walk from the soil into container drainage holes.

Drought stress

Salal's thick, leathery leaves can tolerate dry conditions better than most ericaceous plants, but persistent drought causes the leaf margins to brown and curl inward, and the plant to show general decline. In its Pacific Northwest native range, salal can survive summer droughts because its root system is extensive and deep; in UK containers or in dry woodland soils with competition from tree roots, the plant is more vulnerable. The key requirement is that salal must be adequately established before it experiences drought; newly planted salal should be watered through the first two summers.

What to do

Water during prolonged dry spells in the first two to three years after planting. Apply a deep mulch of composted bark, pine needles, or leaf mould around the root zone to conserve moisture and maintain acidity. Water container-grown salal regularly in summer; check the compost moisture every two to three days. Once well established in the ground, salal is among the most drought-tolerant ericaceous plants and rarely needs irrigation in a typical UK climate.

Alkaline soil

Salal requires acidic soil (pH 4.5 to 6.0); in neutral or alkaline soils, iron and manganese deficiency causes interveinal chlorosis (yellowing between the leaf veins), leaf distortion, and poor growth. Lime from concrete, wall footings, or mortar in urban gardens frequently raises soil pH locally and can cause persistent lime-induced chlorosis on salal planted near buildings or paths. Salal is less acid-dependent than bilberry or bog rosemary, but it still fails in alkaline conditions.

What to do

Test the soil pH; the target is 4.5 to 6.0. Apply iron chelate (sequestered iron) to address an immediate deficiency. Work in ericaceous compost and composted bark at planting. Avoid liming anywhere near salal. In alkaline gardens, grow salal in raised beds or large containers of ericaceous compost, watered with rainwater.

Phytophthora root rot

Phytophthora cinnamomi and related species can affect salal in waterlogged or poorly drained conditions, causing progressive yellowing, leaf curl, and wilting from the outside of the plant inward. The roots are brown and mushy rather than white and fibrous. Salal in heavy clay soil or in depressions where water pools is most at risk; it prefers well-drained conditions despite needing moisture.

What to do

Improve drainage before planting by adding grit or raising the bed. Ensure containers have drainage holes and do not sit in standing water. Remove mushy roots if repotting and treat with a phosphonate-based drench (Fosetyl-aluminium) to reduce Phytophthora severity. Allow the soil to partially dry between waterings.

Frequently asked questions

Why are my salal leaves curling?

Salal (Gaultheria shallon) leaves curl most commonly because of vine weevil root damage, drought stress, or alkaline soil. Vine weevil larvae feed on the roots in autumn and winter; adult weevils notch rounded bites from the leaf margins in summer. Drought causes the leathery leaves to brown at the margins and curl inward. Alkaline soil above pH 6.5 causes interveinal chlorosis and leaf distortion.

What is salal used for in floristry?

Salal is one of the most widely used decorative foliage plants in the global florist trade, sold as "lemon leaf" or "box leaf." The glossy, dark green, leathery leaves are harvested from wild stands in the Pacific Northwest of North America (Oregon, Washington, British Columbia) and exported worldwide. Stems last 2 to 3 weeks in arrangements. UK florists use salal extensively as a filler in bouquets and wreaths.

How do I grow salal in the UK?

Plant in acidic soil (pH 4.5 to 6.0) in a shaded or partially shaded position; salal tolerates dry shade better than most ericaceous plants once established. It spreads by suckers into a dense thicket and can become invasive on acidic soils in western UK. Produces white to pink flowers in late spring and edible dark purple-black berries in late summer. Available from specialist woodland plant nurseries.

How do I control vine weevil on salal?

Apply nematodes (Steinernema kraussei) to moist compost in late August to October; this is the most effective control for vine weevil larvae. Repeat in March. Check for white C-shaped larvae when repotting; remove by hand. Yellow sticky traps capture adults. Do not leave containers on bare soil in summer; adults walk in through drainage holes.