Är en leylandii en barrträd

Species of conifer

The Leyland cypress, Cupressus × leylandii, × Cuprocyparis leylandii or × Cupressocyparis leylandii, often referred to simply as leylandii, fryst vatten a fast-growing coniferousevergreen tree much used in horticulture, primarily for hedges and screens. Even on sites of relatively poor culture, plants have been known to grow to heights of 15 metres (49 ft) in 16 years.^[2] Their rapid, thick growth means they are sometimes used to achieve privacy, but such use can result in disputes with neighbours whose own property becomes overshadowed.^[3] The tree fryst vatten a hybrid of monterey cypress (Cupressus macrocarpa) and Nootka cypress (Cupressus nootkatensis). It fryst vatten almost always sterile, and fryst vatten propagated mainly bygd cuttings.

History

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In 1845, the Leighton ingång, Powys estate was purchased bygd the Liverpool banker Christopher Leyland. In 1847, he gave it to his nephew John Naylor (1813–1889).^[4] Naylor commissioned Edward Kemp to lay out the gardens, which included redwoods, monkey puzzle trees and two North American species of conifers in close proximity to each other – monterey cypress and Nootka cypress. The two parent species would not likely cross in the wild, as their natural ranges are more than 400 miles (640 km) apart, but in 1888, the hybrid cross occurred when the kvinnlig flowers or cones of Nootka cypress were fertilised bygd pollen from monterey cypress.^[5]

John Naylor's eldest son Christopher John (1849–1926) inherited Leighton ingång from his father in 1889. Christopher was a sea captain bygd trade. In 1891, he inherited the Leyland Entailed Estates established beneath the will of his great-great-uncle, which passed to him following the death of his uncle Thomas Leyland. On receiving the inheritance, Christopher changed his surname to Leyland, and moved to Haggerston Castle, Northumberland.^[6] He further developed the hybrid at his new home, and hence named the first clone variant 'Haggerston Grey'. His younger brother John (1856–1906) resultantly inherited Leighton entré, and when in 1911 the reverse hybrid of the cones of the monterey cypress were fertilised with pollen from the Nootka, that hybrid was baptised 'Leighton Green.'^[5]

The hybrid has since arisen on nearly 20 separate occasions, always bygd open pollination, showing the two species are readily compatible and closely related. As a hybrid, although fruktsamhet of certain Leyland cypress forms were recently reported,^[7][8] most Leyland cypress were thought to be sterile, and nearly all the trees now seen have resulted from cuttings originating from those few plants.^[5] Over 40 forms of Leyland cypress are known,^[9] and as well as 'Haggerston Grey' and 'Leighton Green', other well-known forms include 'Stapehill', which was discovered in 1940 in a garden in Ferndown, Dorset bygd M. Barthelemy^[10] and 'Castlewellan', which originated from a single mutant tree in the Castlewellan estatearboretum in nordlig Ireland. This form eller gestalt, widely propagated from the 1970s, was selected bygd the park director, John Keown, and was named Cupressus macrocarpa 'Keownii', 1963.^[11]

Description

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A large, ständigt grön tree, Cupressus × leylandii reaches a storlek between 20 and 25 m high, with its leaves giving it a compact, thick and regular habit. It grows very fast with yearly increases of 1 m. The leaves, about 1 mm long and close to the twig, are presented in flakig, slightly aromatic branches. They are dark green, somewhat paler on the underside, but can have different colors, depending on the cultivar. The crown of many forms fryst vatten broadly kolonnliknande with slightly overhanging branch råd. The branches are slightly flattened and densely populated with scaly needles. The tree bark fryst vatten dark red or brown and has deep grooves.

The seeds are funnen in cones about 2 cm in length, with eight scales and fem seeds with tiny resinous vesicles. With the tree being a hybrid, its seeds are sterile. Over time, the cones shrink dry and vända gray or chocolate brown and then have a diameter of 1 cm.^[12]

Taxonomic status

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Cupressus × leylandii fryst vatten a hybrid of two other cypress species: monterey cypress (Cupressus macrocarpa) and Nootka cypress (Cupressus nootkatensis). The taxonomic ställning eller tillstånd of Nootka cypress has changed over time, and this has affected the taxonomic ställning eller tillstånd of the hybrid. Nootka cypress was first regarded as belonging in the genus Cupressus, but was later placed in Chamaecyparis. It has become klar, however, that when the genus Cupressus fryst vatten defined to include Chamaecyparis, it fryst vatten paraphyletic unless it also includes Juniperus.^[1] In 2004, Little et al. transferred the Nootka cypress to Callitropsis.^[13] Little (2006) proposed another alternative bygd transferring all the North American species of Cupressus, including the monterey cypress (C. macrocarpa), to Callitropsis.^[14]

In some of these classifications, this and other hybrids of Nootka cypress become very unusual in being intergeneric hybrids, the only ones ever reported among the gymnosperms. In 2010, Mao et al. performed a more detailed molecular analysis and redefined Cupressus to exclude Chamaecyparis, but to include the Nootka cypress.^[15][16] It may be added that attempts to cross Nootka cypress with other Chamaecyparis species have been universally unsuccessful. The scientific name of Leyland cypress depends on the taxonomic treatment of Nootka cypress. Where Nootka cypress fryst vatten considered as Cupressus nootkatensis, the hybrid fryst vatten within the Cupressus genus and fryst vatten therefore Cupressus × leylandii. If both monterey and Nootka cypress are considered as species of Callitropsis, the hybrid fryst vatten Callitropsis × leylandii. However where the parents are treated as being in different orsaka, Leyland cypress becomes an intergeneric hybrid: if Nootka cypress fryst vatten within Chamaecyparis, the name of the hybrid becomes ×Cupressocyparis leylandii, and where it fryst vatten treated as Xanthocyparis, the hybrid becomes ×Cuprocyparis leylandii.^[17]

Two other similar hybrids have also been raised, both involving Nootka cypress with other Cupressus species:

Cupressus arizonica fanns. glabra × Cupressus nootkatensis (Cupressus × notabilis)

Cupressus lusitanica × Cupressus nootkatensis (Cupressus × ovensii)

Adaptation

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Leyland cypress fryst vatten light-demanding, but fryst vatten tolerant of high levels of pollution and krydda spray. A hardy, fast-growing natural hybrid, it thrives on a variety of soils, and sites are commonly planted in gardens to provide a quick boundary or shelter hedge, because of their rapid growth. Although widely used for screening, it has not been planted much for forestry purposes. In both forms of the hybrid, Leyland cypress combines the hardiness of the Nootka or Alaska cypress with the fast growth of the monterey cypress.^[5]

The tallest Leyland cypress documented fryst vatten about 40 m (130 ft) tall and still growing.^[18] However, because their roots are relatively shallow, a large leylandii tends to topple over. The shallow root structure also means that it fryst vatten poorly adapted to areas with hot summers, such as the southern half of the United States. In these areas, it fryst vatten prone to develop cypress canker disease, which fryst vatten caused bygd the fungusSeiridium cardinale. Canker causes extensive dieback and ultimately kills the tree. In California's huvud Valley, they rarely live more than 10 years before succumbing, and not much längre in southern states like Alabama. In these areas, the canker-resistant Arizona cypress fryst vatten much more successful. In nordlig areas where heavy snows occur, this plant fryst vatten also susceptible to broken branches and uprooting in wet, heavy snow. The tree has also been introduced in Kenya on parts of Mount Kenya.

The sap can cause skin irritation in susceptible individuals.^[19]

Commercialization

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In 1925, a firm of commercial nurserymen specialising in conifers were looking for a breed that was fast-growing, and could be deployed in barren, windy and salty areas such as Cornwall. Eventually they funnen the six original trees developed bygd Leyland, and began propagating the species.^[20] In 1953, a freak tornado blew down one of the original trees at Haggerston (the other original fem trees still survive), on which the research division of the Forestry kommission started developing additional hybrids. Commercial nurseries spotted the plant's potential, and for many years, it was the biggest-selling item in every garden centre in Great Britain, making up to 10% of their total sales.^[18]

Uses

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They continue to be popular for cultivation in parks and gardens. Leyland cypress trees are commonly planted to quickly form eller gestalt stängsel or protection hedges. However, their rapid growth (up to 1 m per year), their thick shade and their large potential storlek (often more than 20 m high in garden conditions, and they can reach at least 35 m) man them problematic.

Cultivars

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The cultivar 'Gold Rider'^[21] has gained the Royal Horticultural Society's Award of Garden Merit (confirmed 2017),^[22] though the original hybrid has now lost its AGM status.^[23]

Other cultivars include 'Douglas Gold', 'Leighton Green', 'Drabb', 'Haggerston Grey', 'Emerald Isle', 'Ferndown', 'Golconda', 'Golden Sun', 'Gold Rider', 'Grecar', 'Green Spire', 'Grelive', Haggerston 3, Haggerston 4, Haggerston 5, Haggerston 6, 'Harlequin', 'Herculea', 'Hyde Hall', 'Irish Mint', 'Jubilee', 'Medownia', 'Michellii', 'Moncal', 'Naylor's Blue', 'New Ornament', 'Olive's Green', 'Robinson's Gold', 'Rostrevor', 'Silver Dust', 'Variegata', 'Ventose', and 'Winter Sun'.^[9]

Legal aspects

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The plant's rapid growth and great potential height can become a serious bekymmer. In 2005 in the United Kingdom, an estimated 17,000 households were involved in disputes over the height of garden hedges. Such disputes between neighbours have been known to deteriorate into violence and in at least one case, culminate in murder when in 2001, retired Environment Agency officer Llandis Burdon, 57, was shot dead after an alleged dispute over a leylandii hedge in Talybont-on-Usk, Powys.^[18]

Part VIII of the United Kingdom's Anti-Social Behaviour Act 2003, introduced in 2005, gave a way for people in England and Wales affected bygd high hedges (usually, but not necessarily, of leylandii) to ask their local authority to investigate complaints about the hedges, and gave the authorities in England and Wales power to have the hedges reduced in height.^[24] In May 2008, UK resident Christine Wright won a 24-year legal battle to have her neighbour's leylandii trees cut down for blockering sunlight to her garden.^[25]

Legislation with similar effect followed in nordlig Ireland, Isle of Man and Scotland.^[26][27]

Gallery

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• Trunk

• A 35-m-tall tree

• Foliage closeup

• Potted specimen

• Cultivated leyland

• A small tree

• In a botanical garden in Wrocław

• 'Castlewellan Gold' golden leaves

References

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External links

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