About Howea: the palm that outlasted every trend
Howea is a genus of just two species, both found only on Lord Howe Island in the Tasman Sea between Australia and New Zealand. Howea forsteriana, the kentia palm, is the plant you will find in hotel lobbies, period-property hallways, and upmarket conservatories across the UK. Howea belmoreana, the curly palm, has slightly shorter and more arching fronds but is otherwise very similar in its requirements and problems. Both entered cultivation in the Victorian era and quickly became the defining indoor plant of Edwardian grandeur, adorning the first-class cabins of ocean liners and the grand hotels of Europe. Unlike most Victorian plant fashions, the kentia never fell from favour, and for good reason: it is genuinely one of the most tolerant indoor palms ever grown, able to cope with lower light levels, cooler temperatures, and more neglect than almost any other palm species.
Howea are famously slow growing. A plant that fills a 25 cm pot elegantly has often been growing for a decade. This slowness is actually an advantage in an indoor setting because the plant will not outgrow its space quickly, but it does mean that damaged fronds are a real loss. They will not regenerate, and new fronds emerge slowly. Understanding why your howea's leaves are curling, and acting on it early, is the best way to protect those irreplaceable fronds.
The most serious cause: red spider mite
Red spider mite (Tetranychus urticae) is the number one pest of kentia palm in UK indoor conditions, and it is a chronic rather than a one-off problem. The mites are tiny, barely visible to the naked eye, and they colonise the undersides of leaflets where they are protected from casual inspection. As they feed, they pierce individual cells, causing fine bronze or silvery stippling on the upper leaf surface. In a moderate infestation the leaflet edges begin to curl slightly. In a heavy infestation fine webbing appears across the frond surface and the leaves take on an overall bronzed, dull appearance quite different from the healthy glossy green.
The core problem in UK homes and conservatories is central heating. Red spider mites thrive in warm, dry air, and the combination of a heated room through autumn, winter, and spring creates near-perfect conditions for population explosions. A single female can lay hundreds of eggs and populations can double in a week or two in the right conditions.
Get into the habit of inspecting the undersides of leaflets monthly from September through April. A magnifying glass helps. If you see tiny moving dots or early stippling, act immediately. Move the plant away from radiators and heat sources. Raise humidity around the plant with a pebble tray filled with water below the pot, by misting the foliage (though misting alone is not enough), or by grouping plants together to create a more humid microclimate. In a conservatory, the predatory mite Phytoseiulus persimilis is highly effective biological control that will seek out and consume spider mite colonies without harming the plant. For immediate knockdown indoors, insecticidal soap spray applied thoroughly to the undersides of all leaflets works well. Repeat every five to seven days for three to four weeks to break the mite life cycle, as eggs are not killed by most contact sprays.
The second major pest: scale insects
Scale insects are the other persistent pest of howea in UK conditions. Two types appear regularly. Soft brown scale (Coccus hesperidum) produces small oval, flat-to-domed brown shells along petioles and on the undersides of leaflets. Armoured or hard scale species are smaller and more difficult to dislodge. Both types weaken the plant by drawing sap, and both produce honeydew as a byproduct. Honeydew drips onto lower leaves and surfaces below the plant and quickly becomes colonised by sooty mould fungi, turning black. Leaves affected by a scale infestation may yellow and curl as the plant is weakened, and the attractive glossy foliage becomes streaked with black sticky deposits.
Scale infestations build slowly and often go unnoticed until they are well established. Inspect new plants carefully before bringing them near your kentia. Physical removal with a damp cloth or soft brush dipped in diluted washing-up liquid is effective for light infestations. Horticultural oil products smother both scales and eggs. Systemic insecticides applied as a drench can reach sap-sucking pests that contact sprays miss. Unlike red spider mite, scale does not cycle with the seasons in the same way, but populations do grow faster in the warm indoor conditions of a centrally heated home.
Other common causes of curling in howea
Fluoride toxicity. Kentia palm is sensitive to fluoride, which is present in most UK tap water, particularly in hard-water areas. Fluoride accumulates in the leaf tissue over time and causes the characteristic tip-browning that gradually works its way back along the leaflet, eventually causing the tips to curl and die. Switching to collected rainwater or filtered water and flushing the pot through thoroughly every few months to remove accumulated salts will slow or stop new damage, though existing brown tips will not recover.
Drought stress. A kentia in an undersized pot, or one that has been left too long between waterings, will show leaflet curl along the length of the leaflet fairly quickly. The compost will be bone dry, and the pot will feel very light when lifted. Water thoroughly, allow to drain completely, and the plant usually recovers within a day or two.
Overwatering. This kills more kentia palms in the UK than any pest or disease. The roots rot in constantly saturated compost and the plant loses its ability to take up water even when the pot is wet. The fronds yellow and eventually collapse. The compost smells sour. Recovery is possible if caught early by removing the plant from its pot, trimming away any blackened roots, repotting into fresh gritty compost, and holding back on watering. Prevent it from the start by choosing a loam-based compost with added grit rather than peat-based multi-purpose mix, by never leaving the pot sitting in water, and by allowing the top few centimetres of compost to dry before watering again.
Low light. Howea tolerates very low light better than almost any other palm, but in the extremely dark conditions of a UK home in the depths of winter, new fronds can emerge weak, with leaflets that are narrower than normal and that lose the characteristic wide arching form. This is rarely severe enough to cause curling on its own, but it can compound other stresses.
Frequently asked questions
How do I tell red spider mite from scale insects on my kentia palm?
Red spider mite damage shows up on the upper leaf surface as fine bronze or silvery stippling, caused by the mites piercing individual cells on the underside. In heavy infestations you will also see very fine webbing stretched across the fronds. Scale insects, by contrast, are visible as small oval or dome-shaped bumps on petioles and leaf undersides. They also produce honeydew that drips onto lower leaves and turns black with sooty mould. If the foliage looks dusty and bronzed with webbing, suspect mites. If you see sticky residue and black sooty patches, suspect scale.
Is my kentia palm being overwatered or underwatered?
These two problems look similar at first but differ in important ways. Drought stress causes the leaflets to curl along their length quite quickly, the compost pulls away from the sides of the pot, and the pot feels very light when lifted. Overwatering causes the fronds to yellow and eventually collapse, the compost smells sour or musty, and the root ball stays soggy days after watering. Push a finger 5 cm into the compost. If it is bone dry, water thoroughly and allow to drain. If it is still wet from the last watering, hold off and improve drainage. When in doubt, underwatering is far easier to recover from than root rot caused by overwatering.
Why are the leaf tips of my kentia palm going brown and curling?
Tip browning that works its way back along the leaflet is the classic sign of fluoride toxicity in howea. UK tap water, especially in hard-water areas, contains enough fluoride to cause this over time. Switching to collected rainwater or filtered water makes a significant difference. Flush the pot through thoroughly every few months to wash out accumulated salts. Low humidity from central heating can also cause tip scorch that looks similar, so raising humidity around the plant with a pebble tray or grouped plants will help alongside the watering change.
Can my kentia palm recover from a severe red spider mite attack?
Yes, provided the infestation is caught before every frond is severely damaged. Remove the worst-affected fronds cleanly at the base. Treat with insecticidal soap or neem-based spray, covering the undersides of every leaflet thoroughly. Repeat every five to seven days for three to four weeks to break the mite life cycle. Introduce biological control with Phytoseiulus persimilis if you are in a conservatory. Move the plant away from radiators, raise humidity, and inspect monthly going forward. Kentia are slow growing so badly scorched fronds will not regenerate, but the plant will push new growth once the pest pressure is removed.
What is the best watering regime for a kentia palm in the UK?
Allow the top 3 to 4 cm of compost to dry out between waterings. In summer this typically means watering once every ten to fourteen days; in winter, when growth slows and evaporation drops, once every three to four weeks is often enough. Always water thoroughly, letting excess drain freely from the base, and never leave the pot sitting in a saucer of water. Use rainwater or filtered water to avoid fluoride build-up. A good-quality loam-based compost with added grit drains more reliably than peat-based multi-purpose mixes, which hold too much moisture for howea roots.