Ulmus rubra, the slippery elm, is a species of elm native to eastern North America. Other common names include red elm, gray elm, soft elm, moose elm, and Indian elm.
Ulmus pumila, the Siberian elm, is a tree native to Asia. It is also known as the Asiatic elm and dwarf elm, but sometimes miscalled the 'Chinese elm'. U. pumila has been widely cultivated throughout Asia, North America, Argentina, and southern Europe, becoming naturalized in many places, notably across much of the United States.
Ulmus 'Homestead' is an American hybrid elm cultivar raised by Alden Townsend of the United States National Arboretum at the Nursery Crops Laboratory in Delaware, Ohio. The cultivar arose from a 1970 crossing of the Siberian Elm Ulmus pumila with the hybrid N 215, the latter grown from seed sent in 1960 to the University of Wisconsin-Madison elm breeding team by Hans Heybroek of the De Dorschkamp Research Institute in the Netherlands. Tested in the US National Elm Trial coordinated by Colorado State University, 'Homestead' averaged a survival rate of 85% after 10 years. 'Homestead' was released to commerce without patent restrictions in 1984.
Ulmus 'Morton' is an elm cultivar cloned from a putative intraspecific hybrid planted at the Morton Arboretum in 1924, which itself originated as seed collected from a tree at the Arnold Arboretum in Massachusetts. Although this tree was originally identified as Ulmus crassifolia, it is now believed to have been a hybrid of the Japanese elm and Wilson's elm. Accolade has proven to be the most successful cultivar tested in the US National Elm Trial, averaging a survival rate of 92.5% overall.
Ulmus 'Morton Glossy' is a hybrid cultivar raised by the Morton Arboretum, Illinois. Originally named 'Charisma' until it was realized that name had already been registered for another plant, the tree was derived from a crossing of two other hybrid cultivars grown at the Morton: Accolade and Vanguard. Tested in the US National Elm Trial coordinated by Colorado State University, Triumph averaged a survival rate of 86% after 10 years. Triumph was introduced to the UK in 2006 by the Frank P. Matthews nursery in Worcestershire.
Ulmus 'Morton Plainsman' is a hybrid cultivar raised by the Morton Arboretum from a crossing of Siberian Elm and a Japanese Elm grown from openly pollinated seed donated by the Agriculture Canada Research Station at Morden, Manitoba. Tested in the US National Elm Trial coordinated by Colorado State University, Vanguard averaged a survival rate of 78% after 10 years.
Ulmus 'Morton Red Tip' is a hybrid cultivar raised by the Morton Arboretum from an open pollination of Ulmus 'Morton'. The tree has occasionally been reported as a hybrid of Accolade with the Siberian Elm Ulmus pumila, an error probably owing to the commercial propagation of the tree by grafting onto U. pumila rootstocks. Tested in the US National Elm Trial coordinated by Colorado State University, Danada Charm averaged a survival rate of 77.5% after 10 years.
Ulmus 'Morton Stalwart', is a Morton Arboretum hybrid cultivar arising from a controlled crossing of Accolade with the hybrid of a Field Elm U. minor from eastern Russia and a Siberian Elm U. pumila. Tested in the US National Elm Trial coordinated by Colorado State University, Commendation averaged a survival rate of 85% after 10 years.
The Siberian elm cultivar Ulmus pumila 'Green King' was once believed to have been derived from a crossing of the Siberian Elm Ulmus pumila with the American Red Elm Ulmus rubra. However, it is now apparent the tree originated as a sport of U. pumila in 1939 at the Neosho Nurseries, Neosho, Missouri.
The Siberian elm cultivar Ulmus pumila 'Chinkota' was developed from seed of the cultivar 'Dropmore' by the Horticulture & Forestry Department of South Dakota State University c.1955, as one of a seed-produced line of extremely cold-hardy and drought-resistant trees for use in the Great Plains.
The Siberian elm cultivar Ulmus pumila 'Hansen' is a little-known American tree of obscure origin, possibly raised from seed collected by the horticulturist and botanist Prof. Niels Hansen during his expedition to Siberia in 1897.
The Siberian Elm cultivar Ulmus pumila 'Park Royal' is a cold-hardy selection raised by the Sheridan Nursery, Toronto, Ontario, Canada.
The Siberian Elm cultivar Ulmus pumila 'Harbin' is an older Manchurian selection, superseded in the United States by 'Dropmore'. Green reported (1964) a suggestion to merge 'Harbin' and the Siberian elm cultivar 'Manchu' with 'Dropmore', as all came from the Harbin area.
The Siberian Elm cultivar Ulmus pumila 'Manchu' was raised by Stewarts Nurseries, Sutherland, Saskatchewan, c. 1951 from seed collected by Mr Ptitsin from near Harbin, China.
The Siberian Elm cultivar Ulmus pumila 'Pendula' is from northern China, where it is known as Lung chao yü shu. It was classified by Frank Meyer in Fengtai in 1908, and introduced to the United States by him from the Peking Botanical Garden as Weeping Chinese Elm. The USDA plant inventory record (1916) noted that it was a "rare variety even in China". It was confirmed as an U. pumila cultivar by Krüssmann (1962).
The hybrid cultivar Ulmus 'Androssowii'R. Kam., an elm of Uzbekistan and Tajikistan sometimes referred to in old travel books as 'Turkestan Elm' or as 'karagach' [:black tree, = elm], its local name, is probably an artificial hybrid. According to Lozina-Lozinskaia the tree is unknown in the wild in Uzbekistan, and apparently arose from a crossing of U. densa var. bubyrianaLitv., which it resembles, and the Siberian Elm Ulmus pumila. It is sometimes listed as Ulmus × androssowii.
The 'dwarf' elm cultivar Ulmus 'Jacqueline Hillier' ('JH') is an elm of uncertain origin. It was cloned from a specimen found in a private garden in Selly Park, Birmingham, England, in 1966. The garden's owner told Hillier that it might have been introduced from outside the country by a relative. Hillier at first conjectured U. minor, as did Heybroek (2009). Identical-looking elm cultivars in Russia are labelled forms of Siberian Elm, Ulmus pumila, which is known to produce 'JH'-type long shoots. Melville considered 'JH' a hybrid cultivar from the 'Elegantissima' group of Ulmus × hollandica. Uncertainty about its parentage has led most nurserymen to list the tree simply as Ulmus 'Jacqueline Hillier'. 'JH' is not known to produce flowers and samarae, or root suckers.
The Siberian elm cultivar Ulmus pumila 'Pinnato-ramosa' was raised by Georg Dieck, as Ulmus pinnato-ramosa, at the National Arboretum, Zöschen, Germany, from seed collected for him circa 1890 in the Ili valley, Turkestan by the lawyer and amateur naturalist Vladislav E. Niedzwiecki while in exile there. Litvinov (1908) treated it as a variety of Siberian elm, U. pumilavar.arborea but this taxon was ultimately rejected by Green, who sank the tree as a cultivar: "in modern terms, it does not warrant recognition at this rank but is a variant of U. pumila maintained and known only in cultivation, and therefore best treated as a cultivar". Herbarium specimens confirm that trees in cultivation in the 20th century as U. pumilaL. var. arboreaLitv. were no different from 'Pinnato-ramosa'.
The Japanese Elm cultivar Ulmus davidianavar.japonica 'Validation' is a selection made by Kunso Kim and Bethany Brown of the Morton Arboretum released in 2011; propagation is by grafting onto Siberian Elm Ulmus pumila rootstocks.
