W. C. Cheng
Ulmus gaussenii W. C. Cheng, the Anhui, or Hairy, Elm, is a medium deciduous tree whose natural range is restricted to the valleys of limestone mountains in Anhui Province, eastern China. The tree was most commonly found on the flood plains, indicating a tolerance of periodic inundation. However, U. gaussenii is now possibly the rarest and most endangered elm species, with only approximately 30 trees known to survive in the wild. The tree was first introduced to the West in 1995, at the Morton Arboretum, Illinois, as part of an evaluation of Chinese elms for landscape use.
The tree can grow to a height of about 25 m, with a slender trunk < 0.5 m d.b.h. The bark is longitudinally fissured and almost black. The glossy leaves are generally obovate, < 11 cm long, borne on densely pubescent reddish twigs, sometimes featuring flat corky wings. The wind-pollinated apetalous flowers appear in March, the large orbicular samarae < 28 mm diameter ripen in April.
Pests and diseases
The species remains very rare in cultivation in the West. In artificial freezing tests at the Morton Arboretum the LT50 (temp. at which 50% of tissues die) was found to be -30.7 °C. The Anhui Elm was considered of particular interest, as its streamside habitat suggests it may tolerate low oxygen levels.  Very few specimens are cultivated (2017) in Europe, notably in the UK and the Netherlands. There are no known cultivars of this taxon, nor is it known to be in commerce.
The tree is named for Marcel-Henri Gaussen (1891–1981), a French botanist who travelled widely in Asia.
- North America
- Brenton Arboretum, Dallas Center, Iowa. No accession details available.
- Chicago Botanic Garden, Glencoe, Illinois. Planted in West Collections Area.
- Denver Botanic Gardens. Neither acc. no. nor origin disclosed
- Morton Arboretum. Acc. no. 49–95. Wild collected, Anhui Province, China.
- U S National Arboretum , Washington, D.C., USA. Acc. nos. 76224, 68980.
- Grange Farm Arboretum, Sutton St James, Spalding, Lincolnshire, UK. Grafted tree, acc. no. 699.
- Great Fontley Elm Trial Plantation, Butterfly Conservation, Funtley, UK. One sapling planted 2017, grafted on wych elm rootstock.
- North America
- World Conservation Monitoring Centre (1998). "Ulmus gaussenii". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 9 May 2014.
- Grimshaw, J. & Bayton, R. (2009). New Trees - Recent Introductions to Cultivation. RBG Kew, London. ISBN 978-1-84246-173-0
- Ware, G. (1995). Little-known elms from China: landscape tree possibilities. Journal of Arboriculture, (Nov. 1995). International Society of Arboriculture, Champaign, Illinois, USA. 
- Fu, L. & Jin J. (eds). (1992). China Red Data Book. Rare and endangered plants. Vol. 1. Science Press, Beijing
- Fu, L., Xin, Y. & Whittemore, A. (2002). Ulmaceae, in Wu, Z. & Raven, P. (eds) Flora of China, Vol. 5 (Ulmaceae through Basellaceae). Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis, USA. 
- Shirazi, A. M. & Ware, G. H. (2004). Evaluation of New Elms from China for Cold Hardiness in Northern Latitudes. International Symposium on Asian Plant Diversity & Systematics 2004, Sakura, Japan.
- Dirr, M. (2009). 'Future Tree Selections'. Western, Spring 2009, p.8. Western Nursery & Landscape Association, St Joseph, Missouri.
- Brookes, A. H. (2017). Great Fontley Elm Trial, 2017 Report. Butterfly Conservation, Lulworth, England.