Grevillea (family Proteaceae, commonly called spider flower or silky oak) is one of the most spectacular flowering shrubs you can grow in a mild UK garden. The curved styles that give the flowers their spider-like appearance, the fine needle-like or deeply divided foliage, and the months of colour make it genuinely unlike anything in the average British border. But grevillea is not forgiving of two particular mistakes, and curling leaves are almost always the plant announcing one of them.
Cause 1: Cold damage and frost
This is the primary problem in the UK. Most grevilleas sold here carry an RHS hardiness rating of H3, meaning they can tolerate short periods down to around -5°C but need shelter to do so. G. rosmarinifolia and the widely grown G. 'Canberra Gem' both sit at H3. G. victoriae is tougher at H4 and will cope with harder winters, but it is less commonly stocked. G. robusta, the silky oak, is effectively a conservatory plant in most of the UK.
Frost damage shows first at the leaf tips, which turn brown and curl inward. In harder freezes the browning spreads toward the stem and whole branches can die back. Cold wet roots make things significantly worse: grevillea evolved in a climate with dry winters, so waterlogged soil during a frost is more damaging than the air temperature alone suggests. Heavy clay soils hold moisture around the roots in exactly the wrong conditions.
Recovery is possible if the main stems survived. Scratch the bark a few centimetres below the damaged point: green and moist underneath means the stem is alive. Do not cut back until mid-spring, as grevillea is slow to break dormancy and you risk removing wood that would have sprouted. Prune to just above the highest live bud, mulch the root zone, and be patient.
For prevention: plant grevillea against a south or west-facing wall in a sheltered position, particularly in the south-west of England, coastal Wales, or southern Ireland where it can eventually become a large shrub. In colder parts of the country, grow it in a large pot so it can come into an unheated greenhouse or cool conservatory before the first hard frost.
Cause 2: Phosphorus toxicity (the critical hazard)
This one catches out many experienced gardeners because the instinct to feed a struggling or newly planted shrub is well-meaning and usually correct. With grevillea, it can be fatal.
Grevillea belongs to Proteaceae, a family that evolved on some of the most nutrient-depleted soils on earth. Australian proteaceous plants have cluster roots adapted to scavenge phosphorus from soils where it is almost entirely absent. When phosphorus is abundant, those roots absorb it uncontrolled and the plant cannot handle the excess. The result is toxicity that progresses quickly: leaves turn a dark bronze-green, curl, and the plant begins to collapse. In a pot, where nutrients concentrate rapidly, this can happen within weeks of a single application of the wrong product.
The problem fertilisers include most balanced garden feeds (the standard NPK products), bone meal, blood fish and bone, tomato feeds, and most slow-release granules intended for general garden use. Even well-rotted compost from a typical garden heap contains enough phosphorus to cause problems in repeated applications.
The rule is absolute: never feed grevillea with any product that contains phosphorus. Look for fertilisers specifically formulated for Proteaceae, Australian natives, or South African plants. In the UK, a handful of specialist nurseries stock these. Alternatively, use a very dilute seaweed extract in spring, which provides trace elements and potassium without significant phosphorus.
If you suspect phosphorus toxicity has already occurred, flush the root zone with plain water repeatedly to leach out what you can, switch to a phosphorus-free product immediately, and accept that recovery will be slow if the plant has been dosed heavily.
Other causes to consider
Root rot in heavy soil. Grevillea needs genuinely free-draining conditions. In heavy UK clay, the roots sit wet through autumn and winter and begin to rot, which shows as leaf curl and general decline. When planting, mix in a generous quantity of horticultural grit and consider raising the planting level slightly. Avoid mulching directly against the stem.
Spider mite. In sheltered spots, against warm walls, or in glasshouse conditions, spider mite can colonise the fine foliage. Look for fine webbing on the undersides of leaves and a stippled, dusty appearance on the upper surface. Leaves curl and drop in a heavy infestation. Increase air circulation, mist the foliage regularly, and use a suitable pesticide if the infestation is severe.
Drought in containers. Container-grown grevillea in a sheltered sunny spot can exhaust its compost moisture in a single hot day in July or August. Leaves curl as the first sign of stress. Water thoroughly, making sure water drains freely from the base rather than sitting in a saucer. Check the compost daily in warm weather.
Alkaline soil. Grevillea prefers slightly acid to neutral conditions, around pH 5.5 to 6.5. On chalk or alkaline soils the plant cannot access iron and manganese, leading to yellowing between the leaf veins followed by curling and poor growth. On these soils, container growing with ericaceous compost mixed with extra grit is a more practical approach than fighting the ground chemistry.
Grevillea in UK gardens: worth the effort
In the right position, grevillea rewards its owners generously. The flowers are genuinely spectacular, particularly the deep red and pink forms of G. 'Canberra Gem' and G. rosmarinifolia, and they are exceptionally attractive to bumblebees over a long season. In the south-west of England, Wales, and southern Ireland, established plants can reach well over a metre and provide colour from late winter through to summer. The fine-textured foliage looks good year-round against a warm wall, and grevillea has a sculptural quality that few other flowering shrubs can match at similar size.
The three rules that cover almost every UK failure are: no phosphorus fertiliser under any circumstances, genuinely free-draining soil, and a sheltered position out of cold easterly winds. Get those right and grevillea is a more reliable garden plant than its reputation suggests.
Frequently asked questions
Is phosphorus fertiliser really that dangerous for grevillea?
Yes, it can kill the plant within a single season. Grevillea evolved on ancient Australian soils that are almost completely phosphorus-free, so the roots have no mechanism for excluding excess phosphorus. Any balanced garden fertiliser, compost with added nutrients, bone meal, or standard slow-release granules can push the plant into toxicity quickly. The leaves turn a dark bronze-green, curl, and the plant goes into rapid decline. Use only fertilisers labelled for Proteaceae, Australian natives, or specifically described as phosphorus-free.
Which grevilleas are hardy enough for UK gardens?
G. victoriae is the hardiest, carrying an RHS H4 rating, which means it will tolerate most UK winters including moderate hard frosts. G. rosmarinifolia and G. 'Canberra Gem' are both rated RHS H3, making them reliable in the south-west of England, coastal Wales, southern Ireland, and sheltered spots in the south-east, especially against a south or west-facing wall. G. robusta is better treated as a large conservatory plant in the UK except in the very mildest coastal gardens. For most UK gardeners starting out, G. 'Canberra Gem' is the safest bet.
Can grevillea recover from frost damage?
Often yes, if the main woody stems survived. Scratch the bark with a fingernail a few centimetres below the damaged section: green and moist underneath means the stem is alive. Wait until mid-spring before cutting back, as grevillea can be slow to show new growth. Prune to just above the highest point of live wood, and mulch the root zone to protect against further cold snaps. A plant that was killed to the base is unlikely to regenerate unless it was very young and the rootstock remains healthy.
Why are my container-grown grevillea leaves curling in summer?
In summer, the most common cause in a pot is drought stress. Grevillea roots fill a container quickly and the compost can dry out in a single hot day. Water thoroughly until it drains freely from the base, then check again after 24 hours. Use a peat-free, gritty, free-draining compost rather than a moisture-retentive one. If the compost has been refreshed recently with a standard multi-purpose mix, check whether that mix contained added fertiliser, as many do, and phosphorus toxicity can appear quickly in a contained root environment.
Does grevillea need acid soil?
It prefers slightly acid to neutral soil, roughly pH 5.5 to 6.5. On chalk or naturally alkaline soils it will struggle regardless of other care, showing yellowing between the leaf veins (chlorosis) and general poor growth. If your soil tests above pH 7, growing grevillea in a large pot filled with ericaceous compost mixed with extra grit is a more reliable approach than trying to acidify the ground.