Hazel

Лещина – род деревьев и деревянистых кустарников из семейства Березовые (Betulaceae). Название рода происходит от греческого слова «korys», которое переводится как «шлем» или «чехол» (плоды находятся в шлемовидной обертке.

Members of the genus are distributed across the temperate latitudes of the forest zone of East Asia, Europe and North America. In nature they form the understorey in coniferous, broad-leaved and mixed forests; in clearings they expand into dense thickets. Many species are cultivated as nut-bearing plants.

They are fast-growing deciduous shrubs or trees 4-10 m in height. Annual increment can reach 1.5 m. The most active shoot growth occurs in early spring.

Life span 100-150 years. Root system superficial. Crown oval, rounded, pyramidal. Buds scaly, oblong-ovoid, hairy. Branches long, rod-like. Bark of young shoots brown, later becoming light gray.

Leaves simple, round or broadly ovate, often asymmetric, large, up to 20 cm long, toothed, irregularly double-serrated, with large lobate teeth; at the base unevenly ovate, apex acute, glabrous, pubescent along the veins (8-12 veins). In shape they resemble the body of a bream, which is how the plant got its Russian name. Leaf color varies from dark green to light green; there are also cultivars with purple leaves, darker on the upper side; in autumn they turn yellow or red. Leaves unfurl 3-4 weeks after the beginning of flowering.

The plant is monoecious and wind-pollinated. It flowers at about +12°C. Flowers are unisexual. Male flowers are inconspicuous, dense cylindrical catkins that grow on short shoots, develop in autumn, overwinter and open in early spring before the leaves appear. This moment is taken as the starting point in the phenological calendar of plant flowering. Flowers are sessile, solitary, located in the axils of scale-bracts, without a perianth, with two scales. Stamens number four, sometimes forked, as in Corylus avellana ( which can make them appear as eight. Anthers have a tuft of hairs at the tip. Female flowers are gathered in bud-like inflorescences and sit in the axils of bracts two together and have a weakly developed perianth. The ovary is two-celled, inferior, with one ovule in each cell; the style is short with two stigmas, like two red threads, protruding in spring from the bud.

Fruits are single-seeded nuts with a woody involucre. The nuts are surrounded by a tubular, notched covering – the involucre (plyuska), which originated from the bract and two bracteoles or stipules of the female flower. The seed has thick oily cotyledons, without endosperm. The cotyledons remain in the ground during seed germination.

Nuts ripen in September-October.

Species: According to the Royal Botanic Gardens, Kew the genus comprises 17 species:

• Corylus americana – American hazel
• Corylus avellana – Common hazel or cobnut
• Corylus chinensis – Chinese hazel
• Corylus colchica – Colchic hazel
• Corylus colurna – Tree hazel
• Corylus ×colurnoides – Лещина медвежеобразная (hybrid of Corylus colurna and Corylus avellana)
• Corylus cornuta – Beaked (horned) hazel
• Corylus fargesii – Farges's hazel
• Corylus ferox – Ferocious hazel or Himalayan hazel
• Corylus heterophylla – Variable-leaved hazel or Asian hazel
• Corylus jacquemontii – Jacquemont's hazel
• Corylus maxima – Large hazel or Lombardy hazel (fruits called filbert)
• Corylus potaninii – Potanin's hazel
• Corylus sieboldiana – Siebold's hazel
• Corylus wangii
• Corylus wulingensis
• Corylus yunnanensis – Yunnan hazel

According to some sources the genus comprises 20 species:

• Corylus Mandshurica - Manchurian hazel
• Corylus pontica - Pontic hazel
• Corylus thibetica Batalin – Tibetan hazel

Hardiness zone: 5a

Location: Shade-tolerant, but prefers sunny and open sites. With insufficient light leaves are positioned horizontally so as not to shade one another. Does not like cold heavy or overly dry soil. Soil should be moderately moist and rich in nutrients. Groundwater should lie at a depth no shallower than 1 m from the surface.

Planting: Best planted in autumn. Recommended planting scheme – 6x6 m. The root collar must not be covered with soil. The plant is mycorrhizal (requires fungi that coexist with the roots); when planting it is recommended to add a bottom layer of forest litter to a depth of 15 cm. On acidic soils liming is recommended.

Pruning: In the first spring after planting prune above the 5th-6th buds to encourage lateral shoots and root suckers. Plants are usually grown in a bush form; to achieve this remove all excess suckers. To increase yield one can also use a pyramidal, espalier (palmette) or high-stem form. When pruning do not touch young branches that bear male and female flowers. After 20-30 years the trunk requires rejuvenation – complete cutting and covering with fertile soil.

Care: In the second year after planting it is recommended to fertilize the plants with manure or compost. Mineral fertilizers are applied in autumn when male flowers are forming, and also in spring when female flowers are in bloom.

Pests: More than 200 pests have been recorded on hazel; the most common of them are squirrels, the "orehovka" (nut pest), large and medium spotted woodpeckers, the nut weevil, the hazel leafroller, and the bud mite.

Diseases: anthracnose, gray mould and fruit rot.

Propagation: propagated mainly by sowing ripe and selected seeds. It can also be propagated by root suckers or by cleft grafting. Splice grafting and budding are not used. With vegetative propagation it begins to bear fruit in 3-5 years after planting; by seed – in 8-10 years.

Uses: in landscape design used as solitary specimens. Many species are used for creating hedges. It looks excellent in alley plantings. Grown as a food crop. Nuts are used in the confectionery and dairy industries; they are also consumed fresh and dried, and used for oil production.