|Natural range (Florida population excluded)|
Ulmus crassifolia Nutt., the Texas cedar elm or simply cedar elm, is a deciduous tree native to south central North America, mainly in southern and eastern Texas, southern Oklahoma, Arkansas and Louisiana, with small populations in western Mississippi, southwest Tennessee and north central Florida; it also occurs in northeastern Mexico. It is the most common elm tree in Texas. The tree typically grows well in flat valley bottom areas referred to as 'Cedar Elm Flats'. The common name 'cedar elm' is derived from the trees' association with juniper trees, locally known as cedars.
The cedar elm is a medium to large deciduous tree growing to 24–27 m tall with a rounded crown. The leaves are small, 2.5–5 cm long by 1.3–2 cm broad, with an oblique base, and distinguish it from Ulmus serotina with which it readily hybridizes in the wild. Leaf fall is late, often in early winter. The wind-pollinated apetalous perfect flowers are produced in the late summer or early fall; they are small and inconspicuous, with a reddish-purple color. The fruit is a small winged samara 8–10 mm long, maturing quickly after the flowering in late fall.
Migrating monarch butterflies on a cedar elm in central Texas
Pests and diseases
Cedar elm is susceptible to Dutch elm disease (DED), though less so than American elm, and moderately damaged by the elm leaf beetle Xanthogaleruca luteola. The tree also suffers from a vascular wilt, the symptoms often confused with those of DED.
Cedar elms are very susceptible to mistletoe. Mistletoe is a parasite that roots itself in to the vascular system of the tree, thus stealing valuable nutrients and water. In some cases, if not removed the parasite can be devastating to large sections of trees and even fatal. They create club like branches that die out at the ends. These "club" branches create openings for future pests like the elm beetles and carpenter ants. There are no known treatments that are safe enough to kill mistletoe without killing the tree. Removing the mistletoe manually is not a guarantee, however it is the best known method for control.
Owing to Dutch elm disease, the cedar elm is now rarely cultivated in North America. It is extremely rare in cultivation in Europe, and Australasia. Henry (1913) and Bean (1988) note that it does not thrive in northern Europe, where the branchlets often die back. Specimens supplied by the Späth nursery to the Royal Botanic Garden Edinburgh in 1902 as U. crassifolia may survive in Edinburgh as it was the practice of the garden to distribute trees about the city (viz. the Wentworth Elm). A small elm with leaves matching the RBGE's 1902 herbarium specimens of Späth's clone (see External links below) stands in Calton Hill Park (2016), and may be regrowth from one of the three.
- Arnold Arboretum. Acc. nos. 511-2002, 758-86, both wild collected.
- Chicago Botanic Garden, Glencoe, Illinois. No details available.
- Bartlett Tree Experts. Acc. no. 90-1243, unrecorded provenance.
- Morton Arboretum. Acc. no. 385-68, 14-86
- New York Botanical Garden. Acc. no. 79617, unrecorded provenance.
- U S National Arboretum, Washington, D.C., United States. Acc. no. 37834
- Grange Farm Arboretum, Sutton St. James, Spalding, Lincolnshire, UK. Acc. no. 509
- Royal Botanic Garden Edinburgh. Acc. no. 20080090, from seed wild collected in USA.
- Sir Harold Hillier Gardens, UK. Acc. no. 1980-0443, (Brentry Field).
- University of Copenhagen Botanic Garden. No details available.
- Manukau Cemetery & Crematorium, Auckland, New Zealand. No details available.
- "Map: Ulmus crassifolia". Efloras.org. Retrieved 2013-09-01.
- Todzia, C. A. & Panero, J. L. (2006). A new species of Ulmus (Ulmaceae) from southern Mexico and a synopsis of the species in Mexico. Brittonia, Vol 50, (3): 346
- "A New Species of Ulmus (Ulmaceae) from Southern Mexico and a Synopsis of the Species in Mexico". JSTOR 2807778.
- "Ulmus crassifolia in Flora of North America @". Efloras.org. Retrieved 2013-09-01.
- "Plants Profile for Ulmus crassifolia (cedar elm)". Plants.usda.gov. Retrieved 2013-09-01.
- Elwes, H. J. & Henry, A. (1913). The Trees of Great Britain & Ireland. Vol. VII. 1848–1929. Republished 2004 Cambridge University Press, ISBN 9781108069380
- Wilcox, Mike; Inglis, Chris (2003). "Auckland's elms" (PDF). Auckland Botanical Society Journal. Auckland Botanical Society. 58 (1): 38–45.
- Bean, W. J. (1988) Trees and shrubs hardy in Great Britain, 8th edition, Murray, London
- Accessions book. Royal Botanic Garden Edinburgh. 1902. pp. 45, 47.
- American Forests. (2012). The 2012 National Register of Big Trees.
- "''Ulmus crassifolia'' at Morton Arboretum". Cirrusimage.com. 2010-05-06. Retrieved 2013-09-14.
- Ramon Jordan. "US National Arboretum:". Usna.usda.gov. Retrieved 2013-09-01.
- "English". Arboretum-waasland.be. Retrieved 2013-09-01.