Corylus

corylus

( kor - ee - lus )

At-A-Glance Information

This genus of deciduous trees and shrubs need full sun to partial shade and regular water. They are commonly called Filbert or Hazelnut, and have round to oval toothed leaves. Flowers bloom in very early springtime, before leaves appear on branches. Fruits produced by these plants are called Hazelnuts, and are partially surrounded in a protective husk. Use these shrubs and trees as hedges, screens, or in woodland borders. They will draw pollinators and other wildlife into the garden.

corylus Species and Varietals

The genus Corylus includes 14 species, and is generally considered a member of the plant family Betulaceae, though some botanical systems place it under the proposed plant family Corylaceae. Corylus shrubs and trees grow best in USDA hardiness zones 4-9 or Sunset growing zones 2-9 and 14-20, but this varies depending on the species grown. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Corylus americana (American Hazel, American Hazelnut, American Filbert, Cobnut)
This species of deciduous shrubs is native to the eastern and central United States and southern-central Canada. These plants reach between 8 and 16 feet tall and spread out to between 10 and 15 feet. These are often multi-trunked, but can be pruned to be single-trunked and look more like small trees. These shrubs are spreaders, sending up suckers from underground rhizomes. Small mature nuts are edible, ready for harvesting in July through October. Full sun to partial shade is recommended, though production is better in full sun exposure. Best in USDA zones 4-9.

Corylus avellana (European Filbert, Common Hazelnut, Common Hazel)
This shrub reaches 10-15 feet tall and just as wide, and is commercially grown to harvest its nuts. These shrubs are classic hedgerow plants and have been used historically as live agricultural fencing. The species is generally seen between 10 and 26 feet tall, though individual specimens can reach upwards of 50 feet tall. European Filbert thrives in USDA hardiness zones 4-8. There are many varieties; some are listed below:

'Contorta'
(Harry Lauder's Walking Stick)
To 8-10 feet tall and wide. Branches are twisting and gnarled.

'Fuscorubra' ('Atropurpurea')
10-15 feet tall and wide, with reddish-purple foliage.

'Red Dragon'
New growth is red, fading to green. Contorted branches.

Corylus colurna (Turkish Hazel, Turkish Filbert, Byzantine Hazel, Constantinople Hazel, Tree Hazel)
This deciduous species is grown as a tree, and is native to southeastern Europe to western Asia. Turkish Hazel is best in USDA hardiness zones 4-7 or Sunset growing zones 2b-9 and 14-20, and reaches 40-50 feet with a pyramidal shape. This species can be grown as a single or multitrunked tree with flaking, mottled bark. The tree produces small edible nuts and is best in places that experience hot summers and cold winters. Drought-tolerant once established; makes a good urban tree.

Corylus cornuta (Western Hazelnut, Western Beaked Hazel, Beaked Hazelnut)
Leaves are roundish, toothed and hairy, turning bright yellow in fall. Mature shrubs can reach up to 13-25 feet tall when mature, but remain smaller in shade. It is typically multi-trunked. Nuts produced are small with flavorful kernels, and clothed in a leafy husk. Subspecies californica (Western Beaked Hazel) reaches 5-12 feet tall and wide.

Corylus maxima (Giant Filbert, Giant Hazel, Filbert)
Grown as either a shrub or tree, this species is native to southeastern Europe and grows well in USDA hardiness zones 4-8 or Sunset growing zones 2b-9 and 14-17. It is grown commercially for its nuts, reaching 12-15 feet tall and wide at maturity. A widely-grown ornamental form is 'Purpurea', which has deep purple leaves and catkins.

Caring for Corylus

Corylus shrubs and small trees are known for being relatively low-maintenance, and adapt well to a variety of garden settings. They prefer to be planted in a spot in the yard that gets full sun to partial shade, though they will produce more nuts and have better foliage color when exposed to at least 6 hours of direct sun each day. In warmer climates, make sure that they get some late afternoon shade. These trees like well-draining soil, and perform best in loamy soils. If soils are heavy or clayey, it is best to amend the planting site with plenty of organic material before installation. Ensure that enough space is left for these plants when selecting a site; they have a spread of between 10 and 20 feet wide, depending on the variety. If planting in a row, space plants between 15-20 feet apart to accommodate mature size and ensure proper air circulation. Plant so that the root ball is sitting just a bit above the soil level, and ensure that the root flare is exposed. Provide water regularly to new plantings for the first two to three years. Apply a thick layer (between 2-3 inches) of mulch around the base of the tree or shrub to increase soil moisture retention, insulate soil temperature and suppress weed growth. Mature trees are generally drought-tolerant but will need deep waterings during periods of extended drought.

Apply compost yearly around the base of the tree or shrub each year in springtime; avoid over-fertilizing these plants as it can lead to excessive foliage growth at the expense of flowering (and producing hazelnuts). Prune Corylus in late wintertime or early spring before new growth pushes out for the year. At this time, remove any crossing, broken, dead, or diseased branches. They can produce suckers towards the base of the plant; remove these during pruning time. This will prevent the plant from becoming too dense and to direct energy into nut production and canopy growth. Depending on the type and intended use, these plants can be grown as multi-stemmed shrubs or single-trunked trees. These trees and shrubs are long-lived, able to survive for between 20 and 100 years in the landscape before needing to be replaced.

Harvesting Hazelnuts
Hazelnuts, also known as Filberts, grow best in regions that have mild, moist winters and cool summers. Trees won't produce nuts until they are about four years old, and hit their peak production around seven years. Flowers will appear on trees in late wintertime to early springtime, and once flowers have been pollinated, nuts will begin to form. They will grow and mature over the summer months, and be ready for harvesting in October. Once nuts have been harvested, trees go dormant until the next springtime. Once nuts begin to drop, branches of trees can be shaken to loosen the nuts from their attachments, and nuts can be collected from the ground underneath. Remove all plant parts and shells and then soak them in a bowl of water.

Discard any nuts that float, and then inspect the remaining nuts for issues like insect-made holes or any mold. Begin drying nuts within 24 hours of harvesting by laying them out in a single layer, and stirring them around each day. They should be completely dry in between 2 and 4 weeks' time. Once they are dried sufficiently, their meat will be cream-colored and firm. Shelled nuts should be used within a few weeks, and can be stored in a refrigerator. They can also be frozen for up to a year. These nuts are great for eating as a snack on their own, made into nut butters, or added to baked goods or salads.

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