Hakea (family Proteaceae) is one of the more specialist Australian shrubs you can grow in a mild UK garden. Unlike grevillea, which has become relatively mainstream in southern counties, hakea remains the preserve of enthusiasts who appreciate its striking foliage diversity (from rigid needle leaves to broad willow-shaped ones), its compact clusters of small white, pink, or red flowers in winter and spring, and the odd woody seed pods that stay on the plant for years. In the right position, species such as H. sericea, H. lissosperma, H. salicifolia, and H. microcarpa are genuinely rewarding. But hakea will not tolerate two particular errors, and curling leaves are almost always the sign of one of them.
Cause 1: Phosphorus toxicity from fertilisers
This is the most critical hazard for hakea, and it is worth understanding in detail because it runs so strongly against normal gardening instincts.
Hakea evolved on ancient Australian soils that are among the most phosphorus-depleted on the planet. To survive in those conditions, hakea (like all Proteaceae) developed cluster roots, also known as proteoid roots: dense mats of fine rootlets that release compounds to mobilise even the tiniest traces of phosphorus from the surrounding soil. These roots are extraordinarily efficient. When phosphorus is suddenly available in normal garden concentrations, they absorb it without restraint, and the plant has no mechanism to stop the excess entering its tissues. The result is phosphorus toxicity.
Symptoms appear within weeks of exposure and progress quickly. Leaves develop a distinctive dark bronze-green discolouration and curl inward. Shoot tips die back. New growth is stunted and discoloured. In a pot, where nutrients concentrate in a restricted root zone, the plant can collapse within a single growing season.
The products that cause this include almost everything in a typical garden shed: balanced NPK fertilisers, slow-release granules such as Osmocote, bone meal, blood fish and bone, rose feeds, tomato feeds, and most multi-purpose composts with added fertiliser. Standard garden compost, if applied repeatedly, contains enough phosphorus to cause problems over time.
The rule is absolute: never use any product containing phosphorus on hakea. Use only fertilisers specifically formulated for Proteaceae, Australian native plants, or South African plants. A small number of specialist UK nurseries stock these. In their absence, a very dilute seaweed extract in early spring provides potassium and trace elements without meaningful phosphorus. If you suspect toxicity has already occurred, flush the root zone thoroughly with plain water over several days to leach away what you can, stop all feeding immediately, and understand that a heavily dosed plant may not recover.
This is the single most common reason hakea dies in UK gardens. It overtakes even frost damage as a cause of plant loss, because well-meaning fertilisation is far more predictable than a hard winter.
Cause 2: Frost and cold damage
Hakea is generally rated RHS H3, meaning it will tolerate brief dips to around -5°C if given a sheltered position. In practice, this makes it a viable garden plant in mild coastal areas: the Isles of Scilly, Cornwall, sheltered parts of coastal Wales and southern Ireland, and warm south-facing walls in the south-east of England. In colder inland parts of the UK, it should be treated as a conservatory or cool greenhouse subject, or grown in containers that can be brought under glass before the first hard frost.
Cold damage shows first at the needle tips or leaf margins, which brown and curl inward. Cold drying winds do as much harm as hard frost, pulling moisture from the leaves faster than damaged or chilled roots can replace it. In severe weather, entire branches can die back from the tips toward the main stem.
Recovery is frequently possible. Do not cut back immediately after a freeze. Wait until mid-spring, then scratch the bark a few centimetres below the damaged area with a fingernail. Green and moist underneath means the stem is alive. Prune to just above the highest point of living wood, mulch the root zone to insulate against further cold, and be patient. Hakea is slow to break into new growth after a setback. Plants that appear dead sometimes push new growth from near the base, particularly if they were well-established before the cold event.
H. lissosperma, the mountain hakea, is reputedly hardier than most other species and is worth trying in slightly more exposed positions. It has the additional attraction of tolerating some lime in the soil, unlike most of its relatives.
Other causes to consider
Root rot in poorly drained soil. Hakea must have free-draining conditions. UK clay soils hold moisture through autumn and winter precisely when the plant is most vulnerable, and roots sitting in wet cold soil will rot. On heavy ground, significant grit amendment or a raised bed is not optional. Avoid mulching directly against the stem base, which traps moisture at the most vulnerable point.
Drought in containers. Container-grown hakea in a warm sheltered spot can exhaust the compost moisture in a single hot day in July or August. Curling leaves are the earliest signal. Water thoroughly until drainage runs freely from the base, check the compost daily in warm weather, and use a gritty low-nutrient mix rather than a moisture-retentive one.
Red spider mite. In the warm sheltered conditions where hakea does best, particularly against south walls and in conservatories, red spider mite can establish on the foliage. Look for fine webbing on leaf undersides, a dusty stippled appearance on the upper surface, and bronzing. In heavy infestations the leaves curl and drop. Increase air circulation, mist the foliage in the evening during dry spells, and use a suitable pesticide if the infestation is significant.
Hakea in UK gardens
Hakea is genuinely a specialist's plant in the UK, more so than grevillea. Its rewards are different: less about masses of colour and more about the architectural interest of needle foliage forms, the curious woody pods, and the delicate flowers that appear in winter when little else is happening in a mild garden. In areas where the climate allows it to become a good-sized specimen, hakea is a striking companion to other Proteaceae. H. sericea and H. lissosperma with their white winter flowers and rigid needle leaves suit a gravel or paved setting. H. salicifolia with its broader foliage looks more at home in a mixed border against a warm wall.
The no-phosphorus rule applies equally to every other member of the family: grevillea, banksia, protea, leucadendron, and leucospermum all share the same cluster-root physiology and the same vulnerability. If you grow a Proteaceae collection, treat the entire area as a phosphorus-exclusion zone. A single misdirected feed that washes toward a neighbouring plant can cause damage well beyond the intended target.
The three rules that prevent most UK hakea failures are: no phosphorus fertiliser of any kind, genuinely free-draining soil, and a warm sheltered position away from hard frost and cold easterly winds. In the right spot, with the right care, hakea is a more reliable and more interesting plant than most UK gardeners realise.
Frequently asked questions
Is phosphorus fertiliser really dangerous enough to kill hakea?
Yes, and it can happen faster than you expect. Hakea evolved on ancient Australian soils where phosphorus is nearly absent, and the plant has developed cluster roots (proteoid roots) that are exceptionally efficient at absorbing what little exists. When phosphorus is suddenly abundant from a standard garden fertiliser, bone meal, blood fish and bone, or slow-release granules, those roots absorb it without restraint. Toxicity builds rapidly: leaves bronze and curl, shoot tips die back, and a plant that looked healthy in spring can be in serious decline by summer. The only safe approach is to use nothing that contains phosphorus. Fertilisers specifically formulated for Proteaceae or Australian native plants are the correct choice.
How hardy is hakea compared with grevillea in UK gardens?
Most hakeas are broadly similar to grevillea in hardiness, sitting at around RHS H3, which means they need shelter and will struggle in hard winters below about -5°C. H. sericea and H. salicifolia fall into this range and do well against warm south-facing walls in the south-west of England, coastal Wales, and southern Ireland. H. lissosperma is reputedly somewhat hardier than many other species and is worth trying in more exposed positions. By contrast, G. victoriae reaches H4 and is genuinely more tolerant of cold than any commonly grown hakea, so if outright cold hardiness is the priority, grevillea has a small but meaningful advantage. Hakea's appeal lies more in its unusual foliage forms and winter flowering than in toughness.
Can hakea recover after frost damage?
Often yes, provided the main woody stems survived. Scratch the bark a few centimetres below the damaged section with a fingernail: green and moist underneath means that stem is still alive. Resist cutting back until mid-spring, as hakea can be slow to push new growth and it is easy to remove wood that would have sprouted given more time. Prune to just above the highest live point, mulch around the base, and protect from further frosts while the plant recovers. Plants cut to the ground by a severe winter occasionally send up new shoots from near the base, particularly if the rootstock was well established before the freeze.
Why are my hakea leaves curling when the plant is in a pot?
Container hakeas face two specific risks: drought and accidental phosphorus exposure. In warm weather, the compost in a large pot can dry out completely in a day or two, and the first sign is leaf curl. Water thoroughly until it runs freely from the base. More critically, check what compost was used. Many standard potting mixes and multi-purpose composts contain added fertiliser with phosphorus, which can push hakea into toxicity within weeks of repotting. Use a gritty, low-nutrient compost and feed only with a phosphorus-free product formulated for Proteaceae. Never feed with a general-purpose balanced fertiliser.
Does the no-phosphorus rule apply to other Proteaceae in the garden?
Yes, it applies equally across the entire family. Grevillea, banksia, protea, leucadendron, leucospermum, and all other Proteaceae share the same cluster-root physiology and the same vulnerability to phosphorus overload. If you grow a mixed Proteaceae collection, as many specialist enthusiasts do, the rule is simple: no standard garden fertilisers, no bone meal, no blood fish and bone, no general slow-release granules anywhere near any of them. A single misdirected application that washes toward the root zone of a neighbouring plant can cause damage. Use only products clearly labelled as suitable for Proteaceae or Australian and South African native plants throughout the planting area.