Corylus colurna

Corylus colurna, the Turkish hazel, is a deciduous tree native to Eurasia.

Distribution and habitat

It is native to southeast Europe and southwest Asia, from the Balkans through northern Turkey to northern Iran.

Description

It is a large species of hazel, reaching tall, exceptionally to Template:Cvt tall, with a stout trunk up to Template:Cvt in diameter, rarely to Template:Cvt. The crown is slender and conical in young trees, becoming broader and irregular with age. The bark is pale grey-buff, with a thick, corky texture. On young trees, the main limbs are quite small in diameter in relationship to the straight trunk, and arise at almost a 90-degree angle. This makes the tree suitable for urban conditions and helps maintain a symmetrical crown which is popular with landscape architects.

File:20140124Corylus colurna3.jpg

Twig in January with male (yellowish-brown) and female (red) catkins

The leaves are deciduous, rounded, long and Template:Cvt across, softly hairy on both surfaces, and with a coarsely double-serrate to shallowly lobed margin. The buds are ovoid, pale brown. The flowers are produced in late winter or early spring before the leaves; the species is monoecious, with the individual catkins single-sex, but both sexes on the same tree (and often on the same twig); the male catkins are conspicuous, pale yellow and 5–10 cm long, the female very small and inconspicuous, largely concealed in the buds, with only the bright red 1–3 mm long styles visible.

The fruit is a nut and may be known as the Turkish hazel nut, Turkish nut, or Constantinople nut. It is 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 to October and is edible, with a taste that is very similar to common hazel, but is smaller, and has a thicker nut shell. 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. Nut production is irregular and occurs every two to three years

Root

Corylus colurna has fibrous roots. The roots are not adventitious, meaning they do not form suckers. This makes C. colurna desirable for grafting on the rootstock over a single stemmed trees. This allows it to be grown in poorer and rocky soils.

Cultivation

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 C. colurna is tolerant of heat, cold, and drought.

There are no serious pests or problems with C. 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.

Propagation

The most common form of propagation 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 seedlings are large enough to handle, pick the seedlings out into individual pots and grow them on in a cold frame or sheltered place outdoors for their first winter. The seedlings can be planted into their permanent positions in late spring or early summer.

Uses

Besides its use as a single-stem rootstock for C. avellana, C. 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 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, or a specimen tree in parks. It makes a rather formal statement in the landscape due to the tight, consistently-shaped, narrow crown. Other landscape uses for C. colurna are for fruit, difficult and dry sites, and naturalistic areas.

Gallery

• Foliage and immature fruit
  Foliage and immature fruit
• Involucre with ripe nut
  Involucre with ripe nut
• Bristly involucre
  Bristly involucre
• A young Turkish hazel showing the narrow conical crown
  A young Turkish hazel showing the narrow conical crown
• Older specimens become broader, but often retain a good shape
  Older specimens become broader, but often retain a good shape

Related species

Similar species Corylus jacquemontii, once considered as a variety of Coryllus colurna, is found growing wild in the forests of Western Himalayan range in the north Indian state of Himachal Pradesh particularly in the temperate regions of districts of Kullu, Shimla, Kinnaur district and Chamba district.

External links

• Corylus colurna Template:Webarchive - information, genetic conservation units and related resources. European Forest Genetic Resources Programme (EUFORGEN)