Why Are My Scaevola Leaves Curling?

Underwatering

Although scaevola is notably drought tolerant when grown in the ground in its native Australia, the situation is very different for container-grown plants in the UK. The restricted compost volume in hanging baskets and pots dries out rapidly in warm weather, and the plant's relatively thick, succulent-ish leaves curl inward and take on a dull appearance when water stress sets in. Flowering slows and stem tips may droop and wilt in severe cases.

Scaevola in a hanging basket on a warm, sunny day can exhaust the available moisture within hours, especially if the basket is in an exposed or windy position where evaporation is accelerated.

What to do

• Water thoroughly as soon as the top 2 cm of compost feel dry, ensuring water reaches the full depth of the basket or pot.
• In hot or windy weather, check hanging baskets twice a day and water in the morning and again in the evening if needed.
• Adding a water-retaining gel to the compost at planting time significantly reduces watering frequency by holding moisture in the root zone.
• Curled leaves usually recover within a couple of hours of thorough watering if the drought episode has been brief.

Spider mite infestation

Spider mites are a significant pest on scaevola, particularly in warm, dry summers or in sheltered positions where air humidity is low. They feed on the undersides of the thick leaves, causing the upper surface to develop fine silvery or bronze stippling. The affected leaves curl, look dusty or bleached, and fine silky webbing appears between the leaves and stems as the population builds. In severe infestations, the plant stops flowering and the foliage deteriorates rapidly.

What to do

• Examine the undersides of curling leaves for the tiny, barely visible reddish or yellowish mites and their webbing.
• Spray the plant with a strong jet of water, targeting the leaf undersides to physically dislodge the mites.
• Follow up with insecticidal soap or neem oil spray every five to seven days for four to six weeks, ensuring thorough coverage of all leaf surfaces.
• Increasing the humidity around the plant by misting regularly or placing a tray of water nearby inhibits further mite spread.

Overwatering and root rot

Despite its need for regular watering in containers, scaevola will not tolerate persistently waterlogged compost. When the roots cannot access oxygen in saturated compost, they rot, and the plant begins to look progressively worse even though the compost is wet. The leaves yellow, curl, and the stems lose their vitality. Containers without drainage holes, or baskets lined with materials that hold too much moisture, are common culprits.

What to do

• Ensure all containers and baskets have adequate drainage and never leave scaevola sitting in waterlogged saucers.
• Use a free-draining, peat-free compost blended with perlite rather than a heavy, moisture-retentive mix.
• Allow the compost to partially dry between waterings rather than keeping it constantly wet.
• If root rot is suspected, remove the plant, inspect the roots, trim away any dark and mushy material, and replant in fresh, well-drained compost.

Aphid infestation

Aphids occasionally colonise scaevola, clustering on the soft shoot tips and flower buds and feeding on the sap. Their presence causes the leaves near the shoot tips to pucker, distort, and curl, and the flower buds may fail to open normally. Heavy infestations leave behind honeydew, which can promote sooty mould on the leaves. Green or greyish aphids are the most common species encountered on scaevola.

What to do

• Pinch out and dispose of shoot tips with the densest aphid colonies.
• Spray the plant with insecticidal soap every four to five days for two to three weeks, ensuring coverage of shoot tips and leaf undersides.
• A jet of water from a hose dislodges most aphids from the plant quickly and is a useful first step before chemical control.

Nutrient deficiency

Scaevola in containers rapidly depletes the nutrients in potting compost, particularly when it is watering heavily in warm weather, as nutrients leach out with each watering. Without regular feeding, the leaves lose their deep green colour, may curl slightly, and flowering diminishes noticeably. Nitrogen deficiency (general pallor starting with older leaves) and potassium deficiency (leaf edges yellowing or browning then curling) are the most common nutritional problems.

What to do

• Feed scaevola in containers every one to two weeks throughout the growing season with a balanced liquid fertiliser or one formulated for flowering plants.
• Switch to a high-potassium feed (such as a tomato fertiliser) from midsummer to maintain flowering intensity rather than vegetative growth.
• If the compost is more than six to eight weeks old, consider repotting into fresh compost as the slow-release fertiliser incorporated at manufacture will be exhausted.

Frequently asked questions

Why are my scaevola leaves curling?

Scaevola leaves curl most often from underwatering or spider mite infestation. In hanging baskets and small containers, scaevola dries out rapidly in warm weather and the thick leaves curl inward when the plant is water-stressed. Spider mite causes stippling, bronzing, and curling of the leaves alongside fine webbing on the undersides.

How often should I water scaevola?

Scaevola in containers needs watering when the top 2 cm of compost feel dry. In a hanging basket in warm weather, this may mean daily watering. Despite being drought tolerant in the ground, container-grown scaevola has limited compost volume and dries out quickly, so consistent moisture is important for sustained flowering.

Why are my scaevola leaves turning yellow and curling?

Yellow curling leaves usually indicate overwatering, nutrient deficiency, or the approach of the end of the season. Check the compost: if it is persistently wet, overwatering is the likely cause. If the compost is moist but not waterlogged, feed with a balanced liquid fertiliser as the compost may be exhausted.

Does scaevola come back every year in the UK?

Scaevola is frost-tender and is grown as an annual in the UK. It will not survive outdoor winters in most of the country. Plants can be overwintered in a frost-free greenhouse or conservatory and will grow on into the following season, but most UK gardeners treat them as seasonal bedding.