Why Are My Galtonia Leaves Curling?

Waterlogging

Waterlogging is the most common cause of galtonia decline in UK gardens. Galtonia is native to the moist meadows of the Drakensberg mountains in South Africa, where the soil is well-drained despite seasonal rainfall. In persistently waterlogged, anaerobic UK clay, the large bulbs deteriorate and the broad, strap-like leaves curl and yellow as the rotting bulb base fails to support the plant. Waterlogging during winter and early spring is particularly damaging. The large size of galtonia bulbs means they rot more slowly than smaller bulbs, but the damage is no less severe when it occurs.

What to do

• Plant galtonia in well-drained, fertile soil. In heavy clay, work generous amounts of coarse grit and garden compost into the planting area before planting at the recommended depth of 15 to 20 cm.
• Avoid low-lying positions where water collects in winter. A raised bed or sloped position that sheds excess water is ideal.
• In very wet gardens or impermeable clay, lift the bulbs in autumn and store dry until spring replanting, which eliminates the winter waterlogging risk entirely.

Narcissus fly

The large narcissus fly (Merodon equestris) attacks galtonia bulbs as well as narcissus and leucojum. The bumblebee-mimic adult fly lays eggs at the base of the dying leaves in late spring and early summer as the foliage collapses. The larva tunnels into the large bulb and feeds through summer, hollowing out the interior. In the following spring, the damaged bulb produces few, weak, curling leaves but no flower spike, or a stunted and distorted spike. When you dig up the bulb, it feels lighter than expected and the interior is partially or completely consumed. Galtonia's large, accessible bulb neck makes it quite susceptible.

What to do

• Cover the bulb area with fine insect mesh from late spring until midsummer, when adult narcissus flies are active. This prevents the flies from reaching the bulb necks to lay eggs.
• Firm the soil around the base of dying galtonia leaves as they collapse in early summer: this reduces fly access to the bulb necks and the soil surface.
• When dividing established clumps, inspect each bulb for signs of larval damage. Discard any that are soft, hollow, or significantly lighter than expected.

Bulb rot

Fungal bulb rot causes galtonia to produce curling, yellowing leaves or to fail to emerge in spring. The large bulbs deteriorate from the basal plate upward when fungal pathogens attack in wet conditions. Bulb rot is most common in waterlogged soil, in bulbs stored incorrectly before planting, or in bulbs purchased in poor condition. A soft, brown basal plate and unpleasant smell when the bulb is cut are the characteristic signs.

What to do

• Purchase firm, heavy galtonia bulbs and plant promptly in spring. Inspect all bulbs before planting and discard any that are soft, lightweight, or show brown discolouration at the base.
• Dust bulbs with sulphur powder before planting to reduce fungal rot risk.
• Improve drainage in the planting area: this is the most effective preventive measure.

Aphids

Aphids colonise galtonia leaves and flower stems in summer, causing the broad, strap-like leaves to curl as sap is extracted. The flower spike can be distorted if aphids concentrate on the emerging stem. Aphid infestations on galtonia are most common during warm, dry summer weather and can reduce the quality of the flowering display significantly in heavily infested plants.

What to do

• Check galtonia regularly through summer for aphid colonies, particularly on the undersides of the broad leaves and on the emerging flower stems.
• Apply a strong jet of water to knock aphids off the leaves, directing the spray at the undersides. Repeat every few days until the population collapses.
• Apply insecticidal soap spray to persistent or heavy infestations. Encourage ladybirds, lacewings, and hoverflies by providing habitat for beneficial insects in the garden.

Frost damage

Late spring frosts damage the emerging galtonia leaves, causing the tips and margins to curl and brown. Galtonia leaves emerge from late spring onwards and are vulnerable to any late frosts in April and May, though less so than very early-emerging bulbs. In gardens with late frost pockets, the emerging foliage may need some protection. Winter frost damage to bulbs left in the ground is the more serious risk in colder gardens.

What to do

• Cover emerging galtonia growth with horticultural fleece when sharp frost is forecast in spring. The leaves are large enough that covering is straightforward with a supported fleece tent over the emerging shoots.
• In colder gardens, delay planting until April or May when the worst of the frost risk has passed, or plant through a covering of loose organic mulch that provides some insulation.
• In gardens prone to severe winter frost, lift bulbs in October and store dry and frost-free for the winter rather than leaving them in the ground.

Frequently asked questions

Why are my galtonia leaves curling?

Galtonia leaves curl most often from waterlogging or narcissus fly damage. Waterlogging in poorly drained soil causes the large bulbs to deteriorate and the broad, strap-like leaves to curl and yellow. Narcissus fly larvae (Merodon equestris) tunnel into galtonia bulbs over summer and the following season's leaves emerge curled and weak as the hollowed-out bulb cannot support normal growth.

Is galtonia (summer hyacinth) hardy in the UK?

Galtonia candicans (summer hyacinth) is borderline hardy in the UK. It survives outdoors in well-drained soil in sheltered positions in southern England, particularly in the south and west. In colder gardens or heavy clay soils, the bulbs are vulnerable to frost damage over winter and may need lifting in autumn and storing frost-free until spring. A generous mulch of bark or straw applied in late autumn significantly improves outdoor survival rates in marginal areas.

When should I plant galtonia bulbs?

Plant galtonia bulbs in spring from March to May, at a depth of 15 to 20 cm in well-drained, fertile soil in a sunny position. The large bulbs need to be planted deeply to protect them from frost and to anchor the tall flower stems. Galtonia flowers in late summer, from July to September, filling the border season gap between the main summer-flowering perennials and autumn plants. Space bulbs at 20 to 30 cm apart.

Does galtonia need lifting in autumn?

Whether galtonia needs lifting in autumn depends on your garden's climate and soil. In mild areas of the south and west with free-draining soil, galtonia can remain in the ground year-round and gradually naturalises. In colder gardens, in heavy clay, or north of the Midlands, lift the bulbs in October after the leaves die back, allow to dry, and store in a cool, frost-free shed in dry compost or paper bags until April. Replant in spring when frost risk has passed.