Why Are My Nicotiana Leaves Curling?

Aphid infestation

Aphids are the most common cause of leaf curling in nicotiana. They are particularly attracted to the soft new growth at shoot tips and the undersides of young leaves, where they form dense colonies and feed on the plant sap. The sticky surface of nicotiana leaves makes them especially hospitable to aphids, who are partially sheltered by the glandular hairs. Feeding causes the leaves to pucker, distort, and curl around the colony, and the plant's overall vigour declines noticeably in heavy infestations.

Nicotiana's stickiness also means aphids become coated in the plant's secretions, making them more difficult to see than on smoother-leaved plants. Parting curled leaves to check the interior of the curl is important for early detection.

What to do

• Knock aphids off shoot tips and curled leaves with a strong jet of water from a hose.
• Pinch out and dispose of shoot tips with the heaviest aphid concentrations.
• Spray with insecticidal soap every four to five days, ensuring thorough coverage of the undersides of leaves and within curled growth.
• Encourage natural predators: nicotiana's flowers attract beneficial insects including hoverflies whose larvae are voracious aphid predators.

Tobacco mosaic virus

Tobacco mosaic virus (TMV) is particularly relevant to nicotiana, as the plant is in the tobacco family and is a natural host. TMV causes an unmistakable irregular mosaic of dark and pale green or yellow patches on the leaves, accompanied by leaf distortion, puckering, and curling. The mottling is distinctly irregular and affects the whole leaf blade rather than following the pattern of pest feeding. The virus is transmitted by aphids and also, unusually, through contact with infected material including cigarette tobacco.

Smokers handling nicotiana plants can inadvertently transmit TMV from tobacco products to the plant. Washing hands before handling the plant prevents this.

What to do

• There is no cure for TMV. Remove and bin affected plants promptly to prevent spread to other susceptible plants nearby, including tomatoes, peppers, and other members of the Solanaceae family.
• Do not compost plants that show mosaic virus symptoms.
• Control aphid populations on surrounding plants to reduce the risk of virus transmission.
• Wash hands before handling nicotiana and any related plants, particularly if you have been handling tobacco products.

Drought stress

Nicotiana has large, soft leaves that lose moisture rapidly in warm, sunny weather. When the soil dries out between waterings, the leaves wilt and curl inward from the edges. Container-grown plants are particularly vulnerable: nicotiana in a pot on a sunny patio can dry out to the point of wilting within a single day of hot weather. The plants recover quickly from mild drought once watered but repeated stress weakens them and reduces flowering.

What to do

• Water thoroughly as soon as the top 2 to 3 cm of compost feel dry, ensuring water reaches the full depth of the root zone.
• In hot weather, check container plants daily. Mulch around border plants with 5 cm of garden compost to retain soil moisture.
• Wilted nicotiana usually recovers quickly once watered. If a plant does not recover within an hour or two, check for additional problems such as root damage or pest infestation.

Cold damage

Nicotiana is a frost-tender annual that should not be planted out until the risk of frost has passed, typically late May in most of the UK. Young transplants put out too early are frequently caught by late frosts or cold nights, causing the leaves to develop water-soaked patches, curl, turn dark, and collapse. Even without frost, cold winds in early summer can cause the leaf edges to curl and brown on tender young plants that have not been properly hardened off before planting.

What to do

• Harden off nicotiana transplants gradually over two weeks before planting out, starting with sheltered daytime outdoor exposure and gradually increasing duration and exposure.
• Plant out only after late May when night temperatures are reliably above 5 degrees Celsius.
• Cover young transplants with cloches or horticultural fleece if a cold snap is forecast in early summer.
• Cold-damaged plants that retain healthy stem bases often regenerate new growth from the base once temperatures improve.

Whitefly

Whitefly are another common pest of nicotiana, particularly in sheltered positions or on plants overwintered indoors. They congregate on the undersides of leaves, feeding on sap and producing honeydew that promotes sooty mould on the sticky leaf surface. Infested leaves pale, curl, and lose vigour. Disturbing an infested plant causes a cloud of tiny white insects to fly up briefly before resettling on the undersides of leaves.

What to do

• Use yellow sticky traps to monitor and catch adult whiteflies.
• Spray the undersides of leaves thoroughly with insecticidal soap or pyrethrin spray every five days for three to four weeks, as newly emerged adults from resistant pupae require multiple treatments.
• Wipe sooty mould from the sticky leaves with a damp cloth after treating to improve the plant's appearance and light absorption.

Frequently asked questions

Why are my nicotiana leaves curling?

Nicotiana leaves curl most often because of aphid infestation or tobacco mosaic virus. Aphids cluster on shoot tips and leaf undersides, causing the leaves to pucker and curl as they feed. Mosaic virus, transmitted by aphids, causes distinctive yellow and green mottling alongside distortion and curling.

How do I identify tobacco mosaic virus on nicotiana?

Tobacco mosaic virus causes an irregular yellow and green mosaic pattern on the leaves alongside puckering, curling, and distortion. The pattern is not confined to where pests are feeding and typically affects multiple leaves across the plant. There is no cure: affected plants should be removed and disposed of to prevent spread.

Why are nicotiana leaves curling and turning pale?

Pale curling leaves suggest aphid infestation, whitefly, or drought stress. Check the undersides of curled leaves for aphids or whitefly. If no pests are present and the plant is wilting, water stress is the cause.

Can nicotiana recover from aphid damage?

Yes, provided the infestation is controlled before the plant is too weakened. Knock aphids off with water, apply insecticidal soap spray, and allow the plant time to produce new healthy growth. Damaged leaves will not fully recover but the plant produces new foliage quickly in warm weather.