About Clianthus
Clianthus puniceus, known in New Zealand as kaka beak (after the native kaka parrot whose bill the flowers precisely resemble), is a scandent or sprawling semi-evergreen shrub from the family Fabaceae. It produces small, elegantly pinnate leaves and, in spring and early summer, pendant clusters of flowers so striking they stop visitors mid-sentence. The blooms are typically a brilliant, slightly waxy scarlet red, though pink and white forms exist, and they are shaped exactly like a parrot's beak or lobster's claw: long, arching, and hooked at the tip. There is nothing else quite like them in temperate horticulture.
Clianthus was enormously popular in Victorian and Edwardian conservatories, then fell out of fashion, and is now undergoing a well-deserved revival. The Maori considered it sacred. It is now endangered in the wild in New Zealand, where introduced browsing mammals have eliminated much of the natural population, which gives growing it a small conservation dimension as well as an aesthetic one. In UK gardens it is rated RHS H3, meaning it needs a sheltered south or west-facing wall in most areas, or conservatory conditions. In the mildest coastal and south-western parts of Britain and Ireland it can grow freely without wall protection.
When established and well placed, clianthus grows fast, covering a wall section in a few seasons. It is normally propagated from seed, which germinates readily, and is more often sold as seed packets than as named plants in UK nurseries. Prune lightly after flowering to keep the plant shapely and productive.
Why Clianthus Leaves Curl
Cold Damage and Frost
In the UK, cold is the primary reason clianthus leaves curl and the most important thing to understand about the plant. The RHS H3 rating means it can tolerate short periods down to around -5C in a sheltered spot, but the key word is sheltered. Even temperatures that would not trouble a hardier plant can damage clianthus when combined with a drying wind, and a proper frost will cause the pinnate leaflets to curl, wilt, and turn brown progressively from the tips inward. In severe cases the whole plant looks dead: blackened, limp, and collapsed.
The important thing to know is that clianthus very frequently regenerates vigorously from the base or from apparently dead stems after cold damage, even when it looks beyond saving. Do not cut the plant back until late spring, when new growth will confirm which stems have survived and which have not. Scratch the bark: green beneath the surface means the stem is alive. Hold off with the secateurs until you can see clearly what is dead and what is not.
Young plants are far more vulnerable than established, wall-trained specimens with some years of root development behind them. In the coldest UK winters, even mature south-wall plants can be killed outright rather than merely damaged. If you are in a colder part of the country and the plant is in a container, it is worth moving it under glass from November to March. If it is wall-trained, a double layer of horticultural fleece tied loosely around the framework on nights when frost is forecast gives useful protection without causing excessive moisture build-up.
Red Spider Mite
Red spider mite (Tetranychus urticae) is the most serious ongoing pest problem with clianthus, and warm, sheltered south-facing walls and conservatory conditions are almost ideal for it. The mites are tiny, less than a millimetre across, and live on the undersides of the leaflets where they are easy to miss. Their feeding causes a characteristic fine bronzing or stippling across the upper surface of affected leaves: the leaf looks dull, slightly dusty, and lacks its normal healthy sheen. As the infestation builds, affected leaves roll and curl inward. In severe cases a fine webbing appears across the leaf undersides and between leaflets.
The mites breed extremely rapidly in warm dry weather, so populations can go from barely detectable to severe in a matter of weeks during a hot June or July. The key to managing them is getting ahead of the problem rather than reacting to a full infestation.
Increase humidity around the plant: red spider mite dislikes moist conditions. Mist the foliage every few days, paying particular attention to the leaf undersides. Containers should stand on trays filled with damp pebbles. Remove and destroy any heavily affected growth to reduce the breeding population. For plants in conservatories, the biological control agent Phytoseiulus persimilis (a predatory mite that feeds exclusively on red spider mite) is highly effective and should ideally be introduced before populations become severe. For outdoor plants, insecticidal soap sprays applied to the leaf undersides can reduce populations significantly, though repeat applications are needed. Check the undersides of leaflets every week or two from May onwards, especially during warm dry spells, so you catch any outbreak early.
Aphids
Both blackfly and greenfly colonise the soft growing tips and young leaflets of clianthus in spring and early summer. Heavy aphid colonies cause the new growth to curl and distort as it develops, giving a crinkled, stunted appearance to the shoot tips. The damage is unsightly but rarely fatal. Squash colonies by hand, wash them off with a jet of water, or use an insecticidal soap spray. Natural predators including ladybirds, lacewings, and parasitic wasps will usually reduce outdoor populations over time if you give them the chance. Whitefly can cause similar problems in conservatory-grown plants.
Drought Stress
Clianthus needs consistent moisture during the growing season, particularly when wall-trained since the wall itself creates a rain shadow and the soil at the base of a sunny wall dries out faster than open ground. When the plant runs short of water, the pinnate leaves droop and the leaflets curl slightly inward as the plant attempts to reduce moisture loss. Water thoroughly rather than little and often, and apply a mulch of garden compost or well-rotted bark around the base to retain soil moisture and moderate temperature swings.
Waterlogging and Root Problems
Clianthus demands excellent drainage. It is native to free-draining volcanic soils in New Zealand and is intolerant of sitting in wet ground. Waterlogged roots turn brown and rot, and the first visible sign is often leaves that droop, yellow, and curl as the damaged roots fail to deliver water and nutrients to the foliage. If the soil at the base of the plant is consistently wet, improve drainage by incorporating grit or by raising the planting slightly. Clianthus also dislikes root disturbance: repotting or damaging the root system during planting or cultivation can cause a sudden wilting and curling of the foliage that resolves only once the plant re-establishes.
Wall Training
Because clianthus is a sprawling or scandent shrub rather than a self-clinging climber, it needs to be tied in against its support. Fix horizontal wires at 30-centimetre intervals to a south or west-facing wall, or attach a trellis. As new stems extend, tie them in loosely with soft twine, spreading them out to cover the wall evenly. Flat training improves airflow (which helps keep spider mite and fungal problems in check), maximises the warmth the plant receives from the wall, and shows the pendant flower clusters to best effect since they hang freely away from a flat-trained framework.
Frequently Asked Questions
Should I cut back clianthus after frost damage?
No, not immediately. Wait until late spring when new growth starts to emerge, then cut back only the stems that show no signs of life. Dead stems will be brittle and hollow; living stems will still be green or show green beneath the bark when scratched. Cutting back too early removes potentially viable material and can expose the plant to further cold.
How do I prevent red spider mite on clianthus?
Red spider mite thrives in warm, dry conditions, so increasing humidity around the plant is the most effective prevention. Mist the foliage regularly, especially the undersides of leaflets where mites breed. Standing containers on trays of damp pebbles helps. In a conservatory, introduce biological control (Phytoseiulus persimilis predatory mites) before populations build up. Inspect the undersides of leaflets every week or two from May onwards, as early intervention is far easier than controlling a heavy infestation.
How do I train clianthus against a wall?
Clianthus is a scandent or sprawling shrub rather than a true climber, so it needs to be tied in rather than left to self-cling. Fix horizontal wires or a trellis to a south or west-facing sheltered wall. As new stems extend, tie them in loosely with soft twine, fanning them out to cover the wall surface evenly. This improves airflow, reduces pest pressure, and maximises the floral display, since the pendant flower clusters hang beautifully away from a flat-trained plant.
Why are the tips of my clianthus leaflets turning brown and curling?
Browning and curling that starts at the leaflet tips and works inward is a classic sign of frost damage in clianthus. It can also be caused by very dry, cold winds even when the temperature does not drop below freezing, or by drought stress in summer. If the browning appears alongside fine bronzing on the upper leaf surface, red spider mite is a likely cause alongside or instead of cold.
Can clianthus survive outside in the UK?
Yes, in the right position. Clianthus puniceus is rated RHS H3, which means it can survive outside in milder parts of the UK when given a sheltered south or west-facing wall. In very mild coastal and south-western areas it can thrive without wall protection. In colder or more exposed areas it needs the extra warmth and shelter a substantial wall provides. In hard winters even well-established wall plants can be killed, but they often regenerate from the base the following spring.