Alstroemeria, the Peruvian lily, produces some of the most vibrant cut flowers in the garden, with orchid-like blooms in shades of orange, pink, red, yellow, and white carried on stiff stems from late spring well into summer. The plant grows from frost-hardy rhizomes and is more robust than its delicate appearance suggests. When the narrow, lance-shaped leaves start to curl, the cause is almost always either sap-sucking pests or soil-moisture problems rather than disease. Catching the issue early is straightforward once you know what to look for, and most problems resolve quickly with the right treatment.
1. Spider mites
Spider mites are the single most common cause of leaf curl on alstroemeria in summer, especially during hot spells with low humidity. The tiny arachnids colonise the undersides of leaves, piercing cells to feed on sap. This causes a characteristic bronzed or silvery stippling across the upper leaf surface, alongside curling and distortion at leaf edges and tips. A fine webbing between leaves and stems confirms a heavy infestation. Mites reproduce extremely rapidly in warm, dry conditions, so a small problem can escalate to a severe infestation within two weeks.
What to look for
- Silvery, bronzed, or grey stippling on upper leaf surfaces
- Leaves curling inward and yellowing at tips and margins
- Fine webbing across leaf axils and between stems in heavy infestations
- Tiny moving dots on leaf undersides visible with a magnifying glass
- Symptoms worst in hot, dry weather and on plants near walls or fences
How to fix it
Increase humidity around the plant by misting in the early morning and keeping the soil consistently moist. Use a strong blast of water to knock mites off leaf undersides every day or two. Apply insecticidal soap or a diluted neem oil spray thoroughly to all leaf surfaces, including undersides, repeating every five to seven days for at least three applications. Introduce predatory mites such as Phytoseiulus persimilis as a biological control for serious infestations in greenhouses. Avoid broad-spectrum pesticides, which kill predatory insects and mites and often make the problem worse.
2. Thrips
Thrips are slender, fast-moving insects about 1 to 2 mm long that feed by rasping leaf and petal surfaces and sucking up the released sap. On alstroemeria they target both leaves and flowers, causing silvery streaking or flecking on leaves alongside curling, and leaving petals distorted and streaked. Western flower thrips are the most common species and they can transmit impatiens necrotic spot virus, which causes additional ring-spot and bronzing symptoms. Thrips populations peak in warm, dry conditions similar to mites.
What to look for
- Silvery or pale streaking along the length of leaves rather than uniform stippling
- Black or dark specks of thrips excrement on leaf surfaces
- Curling, distortion, and brown edges on leaves
- Flower petals silvery, streaked, or distorted, especially around the margins
- Tiny, fast-moving pale or dark insects visible when disturbed from flowers
How to fix it
Remove and destroy heavily infested leaves and flowers. Apply insecticidal soap or spinosad-based insecticide to leaf surfaces every five to seven days, covering all undersides. Use blue sticky traps to monitor and reduce adult populations. Introduce predatory insects such as Amblyseius cucumeris (a predatory mite that feeds on thrips larvae) as biological control. Keep surrounding weeds cleared, as many act as thrips reservoirs. In protected settings, use reflective mulch beneath plants to confuse thrips.
3. Drought stress
Alstroemeria grows from fleshy rhizomes that store moisture but are genuinely sensitive to soil dryness during active growth. When the soil dries out in summer, the plant redirects water from leaves to maintain the rhizomes and flowering stems, causing the narrow leaves to curl inward along their length and develop a dull, slightly grey-green cast. Newly planted alstroemeria and pot-grown plants are most vulnerable, as their rhizome systems have not yet spread to access deeper soil moisture reserves.
What to look for
- Leaves rolling inward lengthways to reduce transpiration surface
- Dull, slightly grey-green colour rather than fresh bright green
- Soil dry at depth when probed with a finger or skewer
- Symptoms worse on plants in containers or sandy soils
- Partial recovery after deep watering
How to fix it
Water deeply at the base of the plant, soaking the root zone thoroughly rather than little and often. Apply a 5 to 8 cm layer of organic mulch over the root zone to retain moisture and moderate soil temperature. Alstroemeria in containers needs water more frequently than border plants; check soil moisture every two to three days in summer. Avoid wetting the foliage when watering, as damp leaves increase disease risk. In very hot climates, alstroemeria may go dormant in summer; reduce watering during this rest period.
4. Botrytis (grey mold)
Botrytis cinerea, the grey mold fungus, affects alstroemeria in cool, humid or wet conditions, particularly in crowded plantings with poor air circulation. It enters through damaged or senescent tissue and causes a distinctive brown, water-soaked rot that spreads rapidly. Affected leaves curl, develop brown patches, and may collapse. The characteristic grey fluffy spore mass appears on badly infected tissue. Botrytis is most common in spring and autumn and in wet summers.
What to look for
- Brown, water-soaked patches on leaves that spread rapidly
- Leaves curling and collapsing around infected areas
- Grey, fluffy spore masses on infected tissue in humid conditions
- Infection entering through spent flowers, damaged stems, or dense canopy
- Problem worst in cool, damp, still weather
How to fix it
Remove all infected tissue promptly, cutting well below the visible infection point and disposing of material away from the garden. Improve air circulation by thinning out dense clumps and removing dead stems promptly. Avoid overhead watering, especially in the evening. Apply a copper-based or thiophanate-methyl fungicide as a preventive spray in conditions that favour botrytis. Keep the planting area clear of dead leaf litter, which harbours spores over winter.
5. Aphids
Several aphid species colonise alstroemeria, clustering on young shoot tips, stems, and flower buds where they feed on sap. Heavy infestations weaken the plant and cause distortion and curling of young leaves. Aphids also excrete honeydew onto lower leaves, promoting sooty mold growth. The peach-potato aphid and rose aphid are common culprits. Infestations build up quickly in spring when the plant is producing its fastest growth.
What to look for
- Clusters of soft-bodied insects on stem tips, buds, and leaf undersides
- Young leaves curled, distorted, or sticky to the touch
- Honeydew deposits causing leaves to feel tacky
- Black sooty mold growing on honeydew-covered leaf surfaces
- Ants tending colonies on stems, which protect aphids from predators
How to fix it
Pinch or rub out small colonies by hand. Blast heavier infestations off with a firm water jet. Apply insecticidal soap, focusing on stem tips and leaf undersides. Encourage natural predators such as ladybirds, lacewings, and parasitic wasps by avoiding broad-spectrum pesticides. Control ants around the plant if they are disrupting natural biological control. A single application of imidacloprid-based systemic insecticide controls severe infestations but avoid using it on plants in flower to protect pollinators.
6. Root rot
Alstroemeria rhizomes are susceptible to Pythium and Fusarium root rot when grown in waterlogged or poorly drained soil. Infected rhizomes turn soft and brown, lose their ability to take up water and nutrients, and the plant shows classic wilt and curl symptoms even when the soil is wet. Root rot is most common in heavy clay soils, poorly drained borders, and container plants left standing in saucers of water. Conversely, it can also occur in very dry soils that are then overwatered after a dry spell, creating anaerobic conditions.
What to look for
- Leaves curling and yellowing despite consistently moist soil
- Plant wilting even when watered, with no improvement
- Brown, mushy, or foul-smelling roots and rhizomes when dug up
- Problem worse on plants in low-lying or compacted areas
- Lower leaves yellowing and collapsing before upper leaves
How to fix it
Dig up the clump and inspect the rhizomes. Cut away any rotten, soft, or discoloured sections with a clean knife and dust the cut surfaces with sulfur powder or a copper-based fungicide. Allow cut rhizomes to dry for a few hours before replanting. Improve drainage by incorporating grit and organic matter into the planting hole. Replant in a fresh location with better drainage, or into a container with a well-draining loam-based compost. Do not replant in the same infected soil for at least two seasons.
Quick diagnosis checklist
| Symptoms | Most likely cause | First action |
|---|---|---|
| Bronze stippling, webbing, worst in heat | Spider mites | Water jet + insecticidal soap every 5 days |
| Silver streaks, black specks, distorted flowers | Thrips | Remove infested tissue, spinosad spray |
| Lengthways roll, grey-green, dry soil | Drought stress | Deep water + mulch |
| Brown water-soaked patches, grey fluff, cool/wet | Botrytis | Remove infected tissue, improve air circulation |
| Sticky leaves, clusters on shoot tips, ants present | Aphids | Water jet + insecticidal soap |
| Wilt in wet soil, brown roots when dug | Root rot | Dig, trim rotten rhizomes, replant in better drainage |
Frequently asked questions
Why are my alstroemeria leaves curling?
Alstroemeria leaves most often curl because of spider mite infestation in hot, dry weather or thrips feeding on leaf surfaces. Both pests cause characteristic silvery or bronzed speckling alongside the curl. Check the undersides of leaves with a magnifying glass for mites and run a white tissue along a leaf to detect thrips.
How do I get rid of spider mites on alstroemeria?
Increase humidity around the plant and keep the soil consistently moist, as mites thrive in dry conditions. Spray leaves thoroughly with a strong water jet to dislodge mites, covering all undersides. Apply insecticidal soap or neem oil every five to seven days for at least three applications. In severe infestations, miticide products containing abamectin or bifenazate are effective. Avoid broad-spectrum pesticides that kill predatory mites.
Should I cut back alstroemeria when leaves curl?
Yes, if the curling is caused by pests or disease, removing affected stems at soil level encourages fresh growth. Alstroemeria produces new stems continuously from its rhizomes, so cutting back damaged growth does not reduce the plant's overall vigour. This is also the best approach after summer dormancy in hot climates.
Can alstroemeria leaves curl from too much water?
Yes. Waterlogged soil suffocates alstroemeria rhizomes and causes root rot, which leads to yellowing, curling leaves and wilting even when the soil feels wet. The curling from root rot looks similar to drought stress. Check the roots if the soil is consistently wet and the plant still looks stressed, and improve drainage before replanting in fresh soil.
Why do alstroemeria leaves twist and curl?
A distinctive twisting curl where alstroemeria leaves appear to spiral or grow upside-down is actually normal. Alstroemeria leaves are resupinate, meaning they twist 180 degrees as they mature. This is not a problem. Abnormal curling caused by pests or stress looks different: it is irregular, often accompanied by discolouration, and affects the leaf edges or tips rather than the whole blade.