Shrub · Betulaceae
Hazelnut
Corylus avellana
Give it full sun, a pollen partner, and room to spread, and the hazel hangs its branches with nuts each fall.
Full sun
Every 7–14 days
USDA 4–8
12–20 ft · 3.7–6.1 m
Overview
The hazelnut is a hardy, multi-stemmed shrub in the birch family, its several trunks rising and branching from a low crown, native across Europe and into western Asia. Called cobnut or filbert, it carries two things worth a close look: clusters of round, hard-shelled nuts that ripen in autumn and slim suckering shoots that build it into a broad, leafy mass. Hardy from zone 4 to 8, its wood comes through cold winters that split lesser trees.
Before a single leaf unfurls, the bare branches hang with pale yellow catkins, long and dangling and loose enough to shiver in a breath of wind. That wind, not the bee, carries the pollen away, which is why one bush by itself rarely fills its shells. Most hazels are largely self-incompatible, so a second, compatible cultivar must stand nearby for the small female flowers to swell into nuts.
Up close, a well-grown hazel is a dense weave of upright stems clothed in broad leaves. Two things keep that form clean: choosing blight-resistant cultivars whose bark stays sound, and cutting back the slim suckers that keep pushing up from the base and roots. Stay after both and the branching framework holds its shape for decades.
Care
The short version: set it in full sun and deep, well-drained soil, place a compatible pollinizer nearby, water it through the first few years and dry spells, and prune in late winter while cutting out the suckers and any blight.
Light
Hazelnut fills the most shells in full sun, where the extra light ripens more wood and swells more kernels. It carries on in partial shade, but the clusters come in thinner from the shadier ground.
Water
Water it steadily through the first two or three years while the roots drive down, and again through dry spells while the green nuts are sizing in their husks. An established shrub takes drought fairly well, though even moisture always plumps the crop. Let the top half of the soil dry between waterings.
Soil
Plant it in deep, well-drained loam dark with organic matter, though hazel roots take to a wide range of ground, even thin rocky soil over stone. Keep the pH between 6.0 and 7.5, slightly acidic to slightly alkaline.
Temperature
The pale wood and buds are tough, riding out winter lows near -31°F (-35°C) and summer heat up to about 95°F (35°C). The soft point is a hard freeze during the late-winter bloom, which can brown the catkins and cost that year's nuts.
Humidity
Ordinary outdoor air, around 40% to 70%, is all the canopy asks, so there is no figure to chase. Open airflow between the branches counts for more, since it dries the leaves and keeps fungal trouble down.
Feeding
Feed it in early spring before bud break, guided by a soil or leaf test rather than by eye. A nitrogen-rich balanced fertilizer, given seasonally, keeps the shoots green and the nuts filling.
Pruning
Prune in late winter while dormant, when the bare stems show clearly, cutting out dead, weak, and crossing wood and thinning to open the center. Cut any blight cankers well below the visible stromata, and clear the slim basal suckers regularly to hold a tree form.
Repotting
Hazelnut is a long-lived landscape and orchard shrub that spreads its roots in the ground, not in a pot, so it is rarely repotted. A young one raised in a container is potted on before the roots circle the walls, the shoots stall, or water runs straight through the mix.
Size & spacing
A mature hazel builds to 12 to 20 feet (3.7 to 6 m) tall and throws its branches 8 to 15 feet (2.4 to 4.5 m) wide. Give it that much room from its neighbors so air moves through the leaves and the suckers stay in reach for cutting back.
When to plant
The hazelnut moves with the dormant season. New plants go in from late fall to early spring while the branches sleep bare, the pale wind-pollinated catkins open and dangle in late winter, and the ripe nuts brown and drop from late summer into early fall.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Late fall to early spring while dormant
- Harvest: Wind-pollinated catkins open late winter to early spring; nuts ripen and drop late summer to early fall
Hardiness
USDA hardiness zones: 4–8
Temperature: down to -34°C
Troubleshooting
Most hazelnut trouble writes itself onto the plant in one of three places: the bark of the wood, the fill of the nuts, or the crowd of slim shoots around the base. Look closely at those and you can catch a problem early. Match what you see below, then act while it still helps.
Branches dying back beneath rows of raised black bumps on the bark
Run a finger along the bark and you meet raised rows of black bumps set out in football-shaped ranks. That is eastern filbert blight, a fungus whose cankers wrap the wood and starve the branch over a few seasons. Cut the affected limb 2 to 3 feet below the lowest canker and burn or bin the wood, then set out resistant cultivars and clear the wild hazels nearby that keep the fungus alive.
Fix:
- Prune out infected limbs at least 2 to 3 ft below the lowest visible canker and destroy the wood
- Apply protectant fungicides during the spring bud-break infection period
- Replace highly susceptible plantings with resistant cultivars
Catkins hanging thick yet few nuts, or shells that crack open hollow
The pale catkins can dangle in generous numbers and the plant still sets almost no nuts, because hazelnut leans on the wind and can barely pollinate itself. A hard freeze across the late-winter bloom can also brown and finish the catkins or the tiny female flowers. Set a cultivar nearby whose pollen matches and whose bloom overlaps, and choose ground where late frosts land more softly.
Fix:
- Plant at least one cultivar that sheds compatible pollen and overlaps bloom with the main variety
- Site plants where late frosts are less severe
Slim upright shoots crowding the base and roots into a thicket
Slim vertical shoots push up around the trunk and trace the roots, because Corylus avellana suckers freely and, left standing, they knit into a dense thicket. Cut or pull the young shoots while they are still soft, coming back to the task a few times through the season. A pass with the mower or cultivator around the drip line slices the spreading shoots off at ground level.
Fix:
- Cut or pull suckers while young, several times per growing season
- Mow or cultivate around the drip line to sever spreading shoots
Toxicity
For a home with pets and children, the hazelnut carries no poison: it is not toxic. No part of the shrub, leaf or twig or kernel, is listed as harmful, and the ripe nuts are a familiar food. The only real cares are a whole nut lodging in a throat and the upset its heavy fat can bring a dog.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Not a leaf or a scrap of shell on the hazelnut is poisonous to a cat, so a curious nibble leaves it unharmed.
Dogs None
The green parts of the plant are safe for a dog. The hard, round nuts are the catch, since a whole one can lodge in a small dog's throat and the heavy fat inside can upset the stomach or, in quantity, feed a bout of pancreatitis.
Horses Safe
Neither the leaves nor the nuts of hazelnut hold anything that poisons a horse.
Rabbits Safe
The leaves and slender twigs carry no toxins for rabbits, though the rich, oily kernels sit wrong in their diet and are best kept out of reach.
Livestock Safe
Cattle, goats, and sheep can crop the grass around a hazelnut with no toxic effect.
Birds Safe
No part of the plant harms birds, and many wild ones work at the hard shells to reach the ripe kernels inside.
People Safe
The plump ripe kernels are a well-known food, safe to eat raw or roasted, but for anyone with a tree-nut allergy.
Whole nuts are a choking and gastrointestinal obstruction hazard and are high in fat, so large quantities can cause stomach upset and, in dogs, raise the risk of pancreatitis.
Varieties
Named hazels are chosen for blight resistance, for the size and fill of their kernels, or for the shape of their stems. These are the ones worth knowing by name.
Jefferson
A blight-resistant OSU release grown far and wide for its large, plump, high-quality kernels.
Yamhill
A compact, early-maturing OSU cultivar that carries strong resistance to eastern filbert blight.
Barcelona
A traditional Oregon commercial cultivar that falls readily to eastern filbert blight.
Contorta
The ornamental Harry Lauder's Walking Stick, grown for stems that twist and coil into corkscrews for winter interest.
Companions
Plant near
Compatible pollinizer hazelnut cultivar: Supplies overlapping, cross-compatible pollen needed for nut set
Clover or other legume ground cover: Living mulch that fixes nitrogen and suppresses weeds in the orchard floor
Keep apart
Wild or abandoned hazel (Corylus) plants: Act as a reservoir of eastern filbert blight inoculum that infects nearby plantings
How to propagate
The hazelnut roots and grows from several methods, from pinning down a low branch until it takes root to lifting the slim suckers it throws up on its own. The choice depends on whether you want an exact copy of a cultivar or are happy with a seedling.
LayeringModerate
Late winter to early spring · 1 to 2 years to rooted, separable plants
Mound and simple layering root a low shoot to clone a cultivar on its own roots. Pin or heap soil over the low shoots in late winter to early spring, and beneath the mound they grow their own roots over the next 1 to 2 years before you cut them free as new plants.
DivisionEasy
Dormant season, late fall to early spring · 1 season
The slim rooted suckers the shrub throws up make the simplest stock. Lift those rooted basal suckers from an established clump during the dormant season, late fall to early spring, replant them, and they settle in within a single season.
GraftingDemanding
Late winter on dormant rootstock · 1 to 2 years
Grafting binds a named cultivar to a selected rootstock and asks for a steady hand at the knife. Work in late winter on dormant rootstock, and the healing union needs 1 to 2 years to grow into a reliable, productive plant.
SeedModerate
Sow outdoors in fall or stratify cold and moist for 2 to 3 months · Several years to bearing
The round nuts sprout easily enough but won't reproduce the parent, since seedlings don't come true to cultivar. Sow the seed outdoors in fall or chill it cold and moist for 2 to 3 months first, then wait through several years of growth before the plant begins to bear.
Myths
A single hazelnut bush will reliably crop on its own.
Even hung with catkins, a single Corylus avellana rides on the wind and can barely pollinate itself, so one bush usually sets little or no fruit. A separate compatible pollinizer cultivar nearby is what fills the shells with a real crop of nuts.
Hazelnut plants are poisonous to cats and dogs.
The plant is absent from the ASPCA toxic list, and neither its leaves nor its nuts will poison a pet. The real risks are a whole nut lodging in the throat and stomach upset from the heavy fat, not poisoning.