Callitropsis × leylandii
Cupressus × leylandii
Native to (or naturalized in) Oregon:
- Evergreen conifer, to 60-70 ft (18-21 m) tall, 8-15 ft (2.5-4.5 m) wide, columnar to pyramidal form. Leaves scale-like, opposite leaf pairs alternating to form 4 longitudinal rows, individual leaves 1.5-3 mm long, green to bluish-green above and below, arranged in flat sprays on long slender branches. Although fruits rarely, cones are round and about 1.5-2.0 cm wide; it does produce viable seeds.
- Sun. Adaptable and fast growing; can be grown as a hedge (10-15 ft). Grown commercially as a Christmas tree in some areas.
- Hardy to USDA Zone 6
- Long thought to be an intergeneric hybrid of Cupressus macrocarpa (Monterey Cypress) × Chamaecyparis nootkatensis (Alaska Cedar), which occurred many times. (A history of the Leyland Cypress can be found at http://www.leylandii.com/history.html). More recently some consider both of these species to be in the genus Callitropsis, hence Callitropsis macrocarpa and Callitropsis nootkatensis, and therefore the Leyland Cypress would be an interspecific hybrid and named Callitropsis × leylandii. However as of 2019 the accepted name in the ITIS (Integrated Taxonomic Information System) is Cuprocyparis leylandii. But in the USDA's GRIN Leyland Cypress it is listed as × Hesperotropsis leylandii. Apparently this latter designation is based on a paper by Garland and Moore, Taxon 61(3):667-670, June 2012. In any case, ×Cupressocyparis leylandii apparently is no longer an accepted name.
Many cultivars have been selected, including:
- ‘Castlewellan’ (syn.‘Castlewellan Gold’) - vigorous grower, but slower than ×C. leylandii, dense crown, conical to columnar, summer foliage golden yellow in cool regions to greenish yellow in warm climates. Popular. Of seedling origin in 1962 at Castlewellan, North Ireland.
- Emerald Isle® (syn. ‘Moncal’) - foliage bright green, in flat sprays, dense, a Monrovia introduction in 1992, originally from Britain.
- ‘Golconda’ - yellow-gold foliage persists year round, compact pyramid form, fast growing, originally from Briton.
- ‘Gold Nugget’ - bright golden yellow foliage, compact and erect form.
- ‘Gold Rider’ - yellow-golden foliage, in winter yellow with green tips, open, considered one of the best "golden" cultivars. Originated as a branch sport in Holland in the 1980s.
- ‘Naylor's Blue’ - foliage soft to deep blue-green, feather-like (plumose), considered one of the bluest selections, somewhat open form, youngest branches round in cross-section, rarely produces cones. Originated in Leighton Hall, Wales in 1911.
- ‘Robinson's Gold’ - foliage varies from bright gold-yellow to lemon-green, fast growing. Found as a seedling by George Robinson in 1962 in Belfast, North Ireland.
- ‘Silver Dust’ - foliage green with scattered cream-white splashes and streaks, sprays flat. Originated as a branch sport at the U.S. Arboretum, Washington, D.C.
- leylandii: after C.J. Leyland, an English sea captain, who in 1888 reportedly collected seeds from an Alaska Cedar growing on an estate, Leighton Hall, and grew out some of the first hybrids (6 seedlings) and again in 1911 (2 seedlings).
- Oregon State Univ. campus: SE corner Richardson Hall (Emerald Isle™); also a hedge on the east side of the surplus property building at 644 SW 13th St.
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