Leyland cypress and the shifting spectrum of names

Derrick Rooney1

The late Alan Mitchell, dendrologist picked off a Nootka cypress. The Despite the unusual appearance for the British Forestry Commission, seedlings were sent to Haggerston and vigorous growth of the seedlings called it a silvicultural event on Castle, in Northumberland, for they attracted scant interest until a par with the invention of the planting in 1892. The clone later 1926, when they were brought to spade. A British judge called it the named ‘Haggerston Grey’ is one of the attention of William Dallimore, biggest single cause of litigation those seedlings. curator of the British National Pinetum between neighbours in Britain. Many at Bedgebury, who described them In 1911 two similar seedlings were New Zealand farmers who need and arranged for the ‘Haggerston raised at Leighton Hall from shelter in difficult situations regard it Grey’ and ‘Leighton Green’ clones collected off a Monterey cypress. as the best thing since sliced bread. to be propagated. ‘Naylor’s Blue’, These were later named ‘Leighton which grew near ‘Leighton Green’ on “It” is the Leyland cypress, the Green’ (Fig. 1A–B) and ‘Naylor’s a hillside behind Leighton Hall, was archetypal Cinderella tree, which Blue’. propagated only after it was felled by arose as a in England in the a freak windstorm in 1954. A fourth 1880s, was not recognised as special The name “Leyland” commemorates clone, ‘Green Spire’, remains less well until the 1920s, and did not become the family who owned the known. widely known even in Britain until the Haggerston and Leighton estates when the original seedlings were 1960s. The hybrid was a centenarian raised and propagated. C. J. Naylor Dallimore recognised the seedlings by the time the mass-production was managing the Leighton part as that uncommon occurrence, an techniques developed in the 1980s of the estates when the first batch intergeneric cross. The parents were made it available at an affordable of seedlings was raised in the determined to be the Monterey and price for shelter belts in New Zealand. 1880s. In 1892, after inheriting Nootka cypresses. This meant that both the estates, which had been under the international rules then Within the last 20 years, thanks to entailed under the will of his great- in force, a new name, incorporating its vigorous growth and its tolerance great-uncle Thomas Leyland, he moved to Haggerston (taking the bits of both generic names, had of exposure and a wide range of soil hybrid cypresses with him) and to be erected. This was to lead to and climatic conditions, the Leyland changed his surname to Leyland. considerable disruption and confusion cypress has become probably the Subsequently, he sold his lifetime later. second most often planted tree interest in Leighton Hall to his (behind radiata pine) in New Zealand. brother John Naylor, who died in 1906. John Naylor’s son, Captain Some of the clones available have J. M. Naylor, took over Leighton Hall even been talked about as possible in 1909 and remained there until sources of high-quality plantation 1931. He was probably the Naylor of timber. ‘Naylor’s Blue’. Unfortunately, it has another, less desirable, claim to fame. In the last two decades its shifting spectrum of scientific names has caused more confusion for nurseries, farmers, and Fig. 2 Storm-battered macrocarpa growing foresters than any other tree. A on the shoreline, South Bay, Kaikoura. Photo: Derrick Rooney. Leyland cypresses have been in New Zealand only about 60 years, At that time, the Monterey cypress which makes their popularity and was known to taxonomists as rapid spread all the more remarkable, macrocarpa. This species given that they can only be is a native to California and is propagated vegetatively. commonly called “macrocarpa” in New Zealand (Fig. 2). The Nootka The Leyland cypress originated in cypress, also popularly known in the 1883 according to some accounts and American Pacific North-west as yellow 1888 according to others, at Leighton B spruce or yellow cedar, was classified Hall, Welshpool, Wales, as a chance Fig. 1 ×Cuprocyparis ‘Leighton Green’. in the same false-cypress genus as seedling in a batch raised from cones A, shoot. B, foliage. Photos: Derrick Rooney. the better-known Lawson cypress,

1 PO Box 43, Hororata, Canterbury, New Zealand; [email protected]

New Zealand Garden Journal, 2013, Vol. 16(1) 23 and was known as nootkatensis. Nootka cypress is native to the west coast of North America, from Alaska to northernmost California. Dallimore coined the compound generic name ×Cupressocyparis and the specific name leylandii for the Leyland hybrids (Jackson and Dallimore, 1926). The name ×Cupressocyparis was subsequently used for all crosses between the Nootka and other American cypress species. Another two leylandii clones were selected in 1940 from a different source: seedlings from a macrocarpa growing at the small East Dorset town of Ferndown. The seed was raised at Fig. 3 ×Cuprocyparis ‘Silver Dust’, a variegated sport of ‘Leighton Green’. Photo: Derrick Rooney. the Barthelemy nursery at a nearby village, Stapehill, and although no A more recently named Leyland The “original” Leyland clones thrive Nootka cypress was known to be clone, ‘Silver Dust’ (Fig. 3), was almost anywhere in New Zealand growing in the vicinity two unusual raised in the United States from a below the treeline. In the United seedlings were determined to be of the branch sport on ‘Leighton Green’. Its States they are rated for USDA same parentage as Leyland cypress. green foliage is speckled with creamy Hardiness Zone 5 (hardy to -23°C, For many years these seedlings were white variegation at the tips. ‘Silver perhaps lower). known only under the Stapehill code Dust’ is available in New Zealand ‘Leighton Green’ was the first clone numbers, 20 and 21. but it’s not to everyone’s taste. It established in New Zealand. Although can be eye-catching as a specimen In 1956 the research division of it was grown commercially in Britain tree in the right context of other dark the British Forestry Commission from the 1930s little is known evergreen trees but does not make an sent a genetics team to Leighton about early attempts to import it to attractive hedge. Park to collect seed in the hope New Zealand. The first known attempt that new Leyland hybrids could A slower-growing, bright yellow clone, at acclimatisation was made in 1949 be raised from the original source. ‘Robinson’s Gold’, was released in by the North Otago Tree Planting They were unsuccessful in this, the mid-1970s. This was a chance Association, but the failed to but seed collected from an Arizona seedling, found in a rhododendron survive. The association’s minutes, cypress, then known as Cupressus garden near Belfast, Northern held in the North Otago Museum, glabra, growing about 20 metres Ireland. The older ‘Castlewellan Gold’ contain no record of a second attempt from the Nootka cypress that had originated after severe snowstorms in by them. An importation in 1952 by produced the original Leyland clones, the 1962–63 winter snapped a branch the then Department of Agriculture yielded two seedlings that displayed from a golden macrocarpa growing was successful, and the was unusual adult foliage. These were in the forest park at Castlewellan, in established at a research station at subsequently propagated and named County Down. A local nurseryman Rukuhia, near Hamilton, from where ×Cupressocyparis ‘Notabilis’. who sowed seed collected from the propagating material was presumably In 1961 a Mr Howard Ovens, from Tan- fallen branch selected a golden- distributed. coloured seedling that proved to be y-Cae, Dyfed, in Wales, collected seed Harry Hart obtained six plants, via a Leyland-type hybrid. ‘Castlewellan from a Mexican cypress, then known the then Forest Research Institute Gold’ was first marketed in Ireland as , near a grove (FRI) at Rotorua, for planting in in 1970 and has been available in of Nootka cypresses at the Westonbirt the H. E. Hart at Lake New Zealand since the early 1980s. Arboretum in Gloucestershire. Two of Coleridge in 1961, but recorded in his Since 1980 numerous other clones the resultant seedlings were clearly notebook2 that the material supplied and sports of Leyland cypress crossed with Nootka cypress. One of had “weak root systems”. Three have been named in Great Britain, these, commonly known as ‘Ovensii’, plants died in his garden nursery. including some with coloured foliage. is grown in New Zealand and has The remaining three were planted Today, more than 40 Leyland cypress become popular, particularly in the as group No. 80 in the arboretum in have been named. Many North Island, where it seems to grow September, 1961, but two of them of these are almost certainly branch better than it does in the South Island died soon afterwards and the third sports. and produces timber of good quality. was removed in September, 1962.

2 Hart kept a bound notebook in which he recorded, from 1934 until shortly before he died in 1979, detailed observations of acquisition dates, sources, and planting dates of all the trees in the arboretum at Lake Coleridge. His notebook is currently held by the Central Canterbury Farm Forestry Association.

24 New Zealand Garden Journal, 2013, Vol. 16(1) Three replacement plants obtained only about 15 years old and the fact These seedlings, with their obvious from Lincoln University (then Lincoln that logs had been harvested from affinity to the Arizona cypress, were College) were planted as group some of them indicated rapid growth an interesting development, because No. 81 in September, 1962, at which because of the fertility of the site. about the beginning of the present time he noted that they were 2ft 3in century intensive research, including The clone ‘Naylor’s Blue’ was (69 cm) high. His notes say the plants chemical and DNA analysis, in the imported by FRI to Rotorua in 1962, were topped in 1965, but give no United States and Australia indicated and ‘Green Spire’ and ‘Haggerston reason why this was done. Two more that the Nootka cypress was closer Grey’ were brought in by the plants from Lincoln were planted to the New World cypresses than to New Zealand Forest Service a year as group 58, also in 1962 (Hart’s the other Chamaecyparis species. later. The two Stapehill clones were practice was to in groups of This view was reinforced by the fact imported to Lincoln for evaluation in three, with five metres between plants that while the Nootka cypress had 1978 by Dr J. W. “Hamish” Sturrock, and 15 metres between groups). been shown to hybridise with several a scientist at the former DSIR. These All are still there, and now have American Cupressus species, it had were subsequently named ‘Stapehill’ considerable historic significance, never been known to cross with (No. 20) and ‘Ferndown’ (No. 21). as they are the oldest documented another Chamaecyparis, although Four more clones, three identified Leyland cypresses in Canterbury, its natural range overlapped that of only by number and one named and probably in the South Island. the Lawson cypress (Chamaecyparis ‘Rostrevor’, were imported by the Presumably the Lincoln material lawsoniana) in Oregon and it would DSIR in 1985 (Sturrock, 1989), but was ‘Leighton Green’ obtained from have had plenty of opportunity these have not persisted in cultivation the Department of Agriculture, but to do so both in the wild and in in New Zealand. One of the numbered there are no accession records to cultivation. It was also not known to clones failed to survive quarantine confirm this. Leyland hedges growing have hybridised with any Old World and the others were presumably at the university today were planted Cupressus species in cultivation, either discarded as inferior or failed to in the 1970s and 1980s and were although again there would have thrive under trial. probably obtained from commercial been plenty of opportunities for it to sources. There are no specimen All Leyland clones are usually do so, particularly in British collections trees of Leyland on the university considered to be sterile, and there is such as the Bedgebury or Westonbirt campus today. A large solitary tree no overseas record of any of them , where species that was probably the source of producing viable seed. However, from many parts of the world were the Lake Coleridge material was Dr Sturrock found fertilised cones planted in close proximity. removed because of canker in the in a trial planting of Leylands near When the Nootka cypress was first 1970s (Roy Edwards, pers. comm.). Mosgiel, in Otago. Seedlings described in 1824 it was placed Leyland cypress was not planted in were raised from these at Lincoln, in Cupressus but in 1840 it was the Christchurch Botanic Gardens and when Dr Sturrock retired he reclassified as Chamaecyparis until 1977, when a plant of ‘Leighton was given permission to take the nootkatensis on the basis of its Green’ was obtained from the seedlings with him for evaluation on foliage being in flattened sprays, like Christchurch City Council nursery in his lifestyle property at Rangiora. those of the Lawson cypress, and Linwood. This plant is still growing in These F hybrids proved to be a 2 its cones having only four scales, the Pinetum at the Gardens, but is mixed bag, with variable shape, size, whereas other North American affected by canker (Dean Pendrigh, and growth form. The pollen parent and Mediterranean cypresses had curator of collections, Christchurch (or parents) remained unknown, but cones with six or more scales. Both Botanic Gardens, pers. comm.). the appearance of several of the characters were of doubtful value, seedlings suggested that the most At that time Leyland cypresses were because some Chinese Cupressus likely candidate was an Arizona still uncommon in New Zealand and species also have flattened foliage cypress, a common component the few nurseries that listed them sprays or four cone scales. In 2000, of shelter belts in the area. The were selling them at specimen-tree Nootka cypress was transferred back collection was apparently destroyed prices, although their growth form, to (Gadek after Dr Sturrock died but before with its heavy, low branching, was et al., 2000). As a result, Dallimore’s this was done the best of them not suitable for a specimen tree. ×Cupressocyparis leylandii became was selected and propagated by An Ashburton farmer, the late Bill plain Cupressus ×leylandii, which, if the Southern Cypresses nursery at Buchan, was one of the first to grow nothing else, made the name a lot Ohoka. One of these F hybrids is Leyland cypress in Mid Canterbury, 2 easier to spell and pronounce. included in the Central Canterbury probably in the late 1960s. He Farm Forestry Association’s cypress Soon afterwards, the name changed established a small woodlot of trial at its experimental area at again, as a result of the discovery in Leyland cypress on a very fertile Silverwood. When the five clones in 1998, far away in the mountains of site behind his house alongside the the trial were measured in October northern Vietnam, of a rare conifer Ashburton River. At a field day in the 2012, the Sturrock clone ranked completely new to science. The late 1980s he was able to display fourth in growth rate and third when “new” conifer, dubbed “Vietnamese bowls and other items that had been assessed for form and canker golden cypress”, was found by a turned from timber harvested from resistance. joint expedition of botanists from this woodlot. The trees were probably Vietnam, Russia, the United States,

New Zealand Garden Journal, 2013, Vol. 16(1) 25 and England. After detailed taxonomic separated by geography: Callitropsis studies it was determined to be the nootkatensis (native to western closest known relative of the Nootka North America; Fig. 4A–B), and cypress. C. vietnamensis (native to moist karst forest in northern Vietnam). The The Vietnamese tree has hard, effect of this was to leave the Leyland yellow-brown, fragrant, fine-grained cypress without a formal name until timber that is valued highly by local 2006, when Little (2006) transferred residents, which might account for why all the North American species of the scientists found large specimens Cupressus to Callitropsis, a move that only on steep ridges where access once again made a compound name is difficult. “This tree was already for Leyland cypress unnecessary. rare and endangered when we However, Adams and others rejected discovered it,” an American member this classification in 2009, and on the of the botanical team was reported as basis of molecular and DNA analysis saying. The species is unusual in that transferred all Western Hemisphere mature specimens carry both juvenile cypresses except the Nootka cypress and adult foliage. to a new genus, Hesperocyparis To accommodate it and its Nootka (Adams et al., 2009). This move relative, Aljos Farjon, then head of the has been widely accepted in North temperate section of the herbarium America (where the new name is at the Royal Botanic Gardens, Kew, included in the USDA plant database) erected in 2002 a new genus, named and many other countries, including Xanthocyparis (Farjon et al., 2002). Australia, and appears to be here The Vietnamese golden cypress then A to stay, although its status is still became Xanthocyparis vietnamensis, listed as “unresolved” at Kew. The while Nootka cypress became name Hesperocyparis appropriately Xanthocyparis nootkatensis. translates as “western cypress”. Some 54 morphological characters, The changes proposed by Adams as well as DNA evidence, were used et al. (2009) affect nearly all the to place Xanthocyparis vietnamensis familiar cypresses grown for as a sister species to the Nootka timber or shelter, including the cypress. The name Xanthocyparis, macrocarpa (Monterey), Mexican, which translates as “golden cypress”, Arizona, and Guadalupe cypresses, seemed perfectly matched to both and most of the species grown trees, given the yellowish colour of for amenity purposes, leaving their sawn timber. Farjon proposed only the nine Old World species a new name, ×Cuprocyparis, for B from the Mediterranean, the the Leyland and other hybrids of Fig. 4 Callitropsis nootkatensis. A, farm Himalaya, and China in the genus the Nootka cypress, but that name planting. B, foliage. Photos: Derrick Rooney. became redundant within two years because further research in North America revealed that Xanthocyparis, however appropriate a name it might have been for the golden cypresses, was invalid under the “oldest wins” rule in the International Code of Botanical Nomenclature. When more than one name has been validly published for a species, as has often happened when taxonomists from different countries have been working independently on the same species, only the first validly published name may be used. In this case, American research uncovered a monospecific generic name, Callitropsis, dating from 1865. A paper published in the American Journal of Botany (Little et al., 2004) transferred the golden cypresses to this obscure genus, which as a result contained two species widely Fig. 5 Cupressus tortulosa has elegantly fine foliage. Photo: Derrick Rooney.

26 New Zealand Garden Journal, 2013, Vol. 16(1) Cupressus, which now includes 2009: All North American cypresses Christenhusz, M.J.M.; Reveal, J.L.; only C. atlantica, C. chengiana, except the Nootka cypress Farjon, A.; Gardner, M.F.; Mill, C. duclouxiana, C. dupreziana, transferred from Callitropsis to R.R.; Chase, M.W. (2011). A new C. funebris, C. gigantea, a new genus, Hesperocyparis classification and linear sequence C. sempervirens, C. tortulosa, and (Adams et al., 2009). Only the nine of extant . C. torulosa. Cupressus tortulosa Old World species remain in the Phytotaxa 19: 55–70. (Fig. 5) is the elegant weeping genus Cupressus. Nootka cypress Farjon, A.; Hiep, N.T.; Harder, D.K.; tree better (but wrongly) known in reverts to Callitropsis, Vietnamese Loc, P.K.; Averyanov, L. (2002). cultivation as C. cashmiriana (Silba, golden cypress to Xanthocyparis. A new genus and species in (Coniferales) from 2009). Hesperocyparis includes 2011: A group of six taxonomists H. arizonica, H. bakeri, H. benthamii, Northern Vietnam, Xanthocyparis from Finland, United States, and vietnamensis. Novon 12(2): H. forbesii, H. glabra, H. goveniana, Britain recommended that the 179–189. H. guadalupensis, H. lusitanica, name Cupressus be conserved Gadek, P.A.; Alpers, D.L.; H. macnabiana, H. macrocarpa, for Callitropsis, Xanthocyparis, Heslewood, M.M.; Quinn, C.J. H. montana, H. nevadensis, and the New World cypresses (2000). Relationships within H. sargentii, and H. stephensonii. until the evolutionary history of the Cupressaceae sensu lato: a Nootka and Vietnamese golden Cupressaceae has been resolved combined morphological and cypresses remain in Callitropsis and (Christenhusz et al., 2011). molecular approach. American Xanthocyparis respectively. These are 2013: Scientific name for Leyland Journal of Botany 87(7): 1044– both monotypic genera. and New World cypresses remain 1057. Here is a chronological sequence of unresolved. The most recent Jackson, A.B. and Dallimore, W. botanical name changes: validly published name for Leyland (1926). A new hybrid conifer. Kew and other hybrids of Nootka Bulletin 3: 113 –115. 1926: Intergeneric name, cypress is still ×Cuprocyparis Little, D.P.; Schwarzbach, A.E.; ×Cupressocyparis, erected for the (Farjon et al., 2002). Adams, R.P.; Hsieh, C-F Leyland cypress by W. Dallimore, (2004). The circumscription curator of the British National Given the widespread use of and phylogenetic relationships Pinetum at Bedgebury (Jackson cypresses, particularly those of Callitropsis and the newly and Dallimore, 1926). from North America, for shelter, described genus Xanthocyparis 2000: Nootka cypress, one of the ornamental, and forestry planting, (Cupressaceae). American parents, transferred to Cupressus, this is a major upheaval affecting Journal of Botany 91(11): 1872– making the compound name thousands of tree-growers, foresters, 1881. unnecessary (Gadek et al., horticulturists, and nurseries. Little, D.P. (2006). Evolution and 2000). Leyland cypress becomes Eventually all of these will probably circumscription of the true Cupressus ×leylandii. have to get used to the new names, cypresses (Cupressaceae: but for the foreseeable future many Cupressus). Systematic Botany 2002: New generic name, will probably dispense with Latin 31(3): 461–480. Xanthocyparis, erected for the names and use accepted common Silba, J. (2009). The of Nootka cypress. New compound names for the cypresses. If nothing the Griffith cypress Cupressus( name, ×Cuprocyparis, erected else, this might for once be less tortulosa Griffith). Journal of the for the Leyland cypress and other confusing. It is important to remember International Conifer Preservation hybrids between the Nootka that throughout these nominative Society 16(1): 45–50. cypress and American cypress disruptions the plants themselves Sturrock, J.W. (1989). Leyland species by A. Farjon, RBG, Kew have not changed. The changes cypress introductions to (Farjon et al., 2002). have occurred in our knowledge and New Zealand. NZ Forestry Journal, November 1989. 2004: Older name, Callitropsis, understanding of their relationships published in 1865, discovered for and evolutionary background. Websites the Nootka cypress (Little et al., The Database: References 2004). The name Xanthocyparis is www..org dropped. Adams, R.P.; Bartel, J.A.; Price, R.A. (2009). A new genus, The history of Leylandii: 2006: All North American cypresses, Hesperocyparis, for the cypresses www.leylandii.com/history.html including the macrocarpa, of the western hemisphere USDA Plants Database: transferred from Cupressus to (Cupressaceae). Phytologia 91(1): http://plants.usda.gov/java/ Callitropsis (Little, 2006). Leyland 160–185. Wikipedia: Leyland cypress: http:// cypress thus becomes Callitropsis en.wikipedia.org/wiki/Leyland_ ×leylandii. Cypress

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