A deciduous tree native to Europe and Asia, turkish hazel, or Corylus colurna, is the largest species of hazel tree. It is often used in landscaping and is tolerant of pollution in urban areas.
I. Appearance and Characteristics
Corylus colurna, the Turkish hazel or Turkish filbert, is a deciduous tree native to southeast Europe and southwest Asia, from the Balkans through northern Turkey to northern Iran.
It is a large species of hazel, reaching 25 m (82 ft) tall, with a stout trunk up to 1.5 m (4 ft 11 in) in diameter; the crown is slender and conical in young trees, becoming broader with age. The bark is pale grey-buff, with a thick, corky texture.
The leaves are deciduous, rounded, 6–15 cm long and 5–13 cm across, softly hairy on both surfaces, and with a coarsely double-serrate to shallowly lobed margin. The main limbs are quite small in diameter in relationship to the straight trunk, and arise at almost a 90-degree angle. Making the tree quite durable to urban conditions and helps maintain a symmetrical crown which landscape architects love so much.
The flowers bloom in early spring before the leaves, and are unisexual, with single-sex catkins; the male pale yellow and 5–10 cm long, the female very small and largely concealed in the buds, with only the bright red 1–3 mm long styles visible. The flowers on female trees are not very visible. On male trees, however, the flowers are visible.
The fruit is a nut sometimes called “Turkish nuts” about 1–2 cm long, surrounded by a thick, softly spiny and bristly involucre (husk) 3 cm diameter, which encloses all but the tip of the nut; the nuts are borne in tight clusters of 3-8 together, with the involucres fused at the base. The fruit matures in September and is edible, with a taste that is very similar to common hazels.
They are occasionally gathered from the wild as well as from urban trees, but their small size (smaller than common hazel nuts) and very hard, thick nut shell (3 mm thick) makes them of little or no commercial value. Corylus colurna is however important in commercial hazelnut orchards, as it does not sucker, making it the ideal rootstock on which to graft the nut-bearing common hazel cultivars. The nut can only be found on female trees. Nut production is irregular and occurs every two to three years.
Corylus colurna has a medium growth rate. It is occasionally drought tolerant and alkaline soil tolerant. However, it prefers moist, well-drained soil, as well as full sun. Once established Corylus colurna is tolerant of heat, cold, and drought.
There are no serious pests or problems with Corylus colurna.
Corylus colurna is not easily transplantable and will need extra watering in summer after transplanting. It will take about two years after transplant for the tree to become established and survive on its own.
Corylus colurna has received the Royal Horticultural Society’s Award of Garden Merit.
II. How to Grow and Care
Turkish hazel is a robust and low-maintenance tree suitable for various landscapes. The plant thrives best in well-drained soils and can adapt to a wide range of pH levels. Special care points include ensuring it has enough space to accommodate its large stature and providing adequate water during its establishment period. Regular maintenance is minimal, making turkish hazel an easy plant to care for.
Sunlight
Turkish hazel thrives in full sun, flourishing with exposure to bright and direct light for a majority of the day. This optimal intensity contributes to vigorous growth and maximizes health capabilities, including the production of robust foliage and potential nut yield. However, turkish hazel also possesses a commendable tolerance for partial sun, adjusting relatively well to situations with lighter sun exposure.
While turkish hazel endures less than ideal levels of light, significant variances from full sun may result in reduced growth vigor and lower nut production. Adaptively, turkish hazel’s leaves may adjust to optimize light absorption under varying conditions. Recommended planting locations for turkish hazel are in outdoor environments where sunlight is abundant.
Watering
Adapted to the temperate climates of its native habitat, turkish hazel thrives with moderate moisture and displays a preference for well-drained soils. It is relatively drought-tolerant once established, needing minimal supplemental watering, roughly once every three weeks. This schedule reflects its resilience and ability to adapt to drier conditions. Typically grown outdoors due to its size and growth habit, turkish hazel benefits from mulching which helps retain soil moisture, particularly important during its active growing season.
Fertilizing
For Turkish hazel, spring fertilization with a balanced feed supports robust growth; in late summer, switch to high nitrogen to prepare for dormancy. Annually, 2-3 applications, incorporating 1 pound per inch of trunk diameter, are sufficient. Over-fertilization risks growth at the expense of nut production. In different growth stages, adjust quantity—less for young, more as turkish hazel matures. Always water deeply post-application to prevent root burn. Seasonal changes dictate less in fall, ceasing in winter. Mulching post-fertilization retains nutrients and moisture.
Propagation
The most common form of propagation for Corylus colurna is by seed. It is best sown as soon as it is harvested in autumn in a cold frame. The seed will germinate in late winter or spring. If starting with a stored seed, the seed should be pre-soaked in warm water for 48 hours and then given 2 weeks warm followed by 3 to 4 months cold stratification. This will allow the seed to germinate in 1 to 6 months if kept at 20 °C.
Once the seed is large enough to handle, pick the seedlings out into individual pots and grow them in a cold frame or sheltered place outdoors for their first winter. You can plant the seed into their permanent positions in late spring or early summer.
Transplanting
The optimal window for relocating turkish hazel is when nature awakens in late spring or as it unwinds into mid-fall. Choose a spot with well-drained soil and some sun protection. Gentle handling aids root preservation for Turkish hazel’s success.
III. Uses and Benefits
Besides its use as a single-stem rootstock for Corylus avellana, Corylus colurna is widely cultivated as an ornamental tree in Europe and North America. It is very tolerant of difficult growing conditions in urban situations, which in recent decades has increased its popularity in civic planting schemes. Turkish hazel makes a good shade tree since it produces very dense shade, and its narrow crown and ability to withstand air-pollution make it well suited for use as a street tree in urban areas. It makes a rather formal statement in the landscape due to the tight, consistently-shaped, narrow crown. It is well suited for areas which have restricted overhead.
Corylus colurna is also used in different sized parking lot islands and a variety of wide lawns. It is recommended for a buffer strip around parking lots or highways. Also it is used as a street tree, specimen tree, or in sidewalk cutouts. Other landscape uses for Corylus colurna are for fruit, difficult and dry sites, naturalistic areas, and street trees.