| 0 | Ames 33357 | JDC/UT/2016/018/733 | Ulmus thomasii Sarg. | Iowa, United States | NC7 |  | | 2016 | COLLECTED | 06/03/2016 | Malanaphy Springs State Preserve just northwest of Decorah, T99N R8W SW ¼ NW ¼ SE ¼ Sec. 31 | 43.34713800, -91.83840000 | 302 | Deciduous woods. Rocky substrate. 20 degree northwest-facing slope | Wild material | Ulmus thomasii (Rock elm) is an underutilized tree species both in conservation and in the urban landscape. Charles Sprague Sargent (first director of the Arnold Arboretum of Harvard University, Boston, MA) described the wood of Rock Elm as "heavy, hard, very strong and tough, closely grained, and susceptible of receiving a beautiful polish". Historically noted for a variety of uses in woodworking including furniture, heavy agricultural implements, timber frame buildings, pianos, hockey sticks, and hand tools. U. thomasii is extremely drought tolerant, adaptable to very calcareous soils, and compared to U. americana or U. rubra has a very conservative growth rate requiring minimal attention in regards to pruning. Rock elm naturally tends to develop into a nice structural specimen in the landscape, unlike other fast growing U. americana cultivars in the nursery trade needing frequent attention. Rock elm has very fissured bark and is well known for maintaining a strong central leader resulting in a very attractive, pyramidal form. Despite many literature sources stating that "wings" on the stems are a key identifiying characteristic, this trait is not reliable and many genotypes may completely lack "wings" on the stems. While growth habit and morphology of dormant buds (very pointy) are good traits to help aid in identification, fruits are the best way to confirm identity. Fruits are densly pubescent, often described as "inflated" and generally reach maturity a couple weeks after U. rubra and U. americana. U. thomasii flowering in central Iowa typically occurs the last week in April into the first week in May and are rather distinguishable from other Ulmus in being pendulous. Fruits are extremely prized treats for many birds, where fruits are often "robbed" prior to full maturity. Fruits are also highly prized by many other animals such as mice, squirrels, chipmunks, turkeys, etc. and are generally consumed within hours after fruit abscission. The native range of U. thomasii is concentrated in the northeastern United States and into Canada with disjunct populations documented in northwestern Missouri and northwestern Arkansas (Little, E. L. Jr. 1971). In the 1895 Silva of North America (vol. 7) it was stated that, “The value of the wood of the Rock Elm threatens its extinction and most of the large trees have already been cut.” Today, since rock elm is rather rare, especially in areas near the edges of its range, many states list the species as endangered or threatened warranting preservation efforts. This accession represents genetics from northeast Iowa (Winneshiek County). In an assessment of some of the largest Ulmus thomasii (native and cultivated) across Iowa, four of the nine largest specimens in Iowa are present in Malanaphy Springs State Preserve where this accession was sampled. The second largest U. thomasii in the state located in Malanaphy Springs was measured on 22 May 2020 with a circumference of 6.42', height of 86.58', and an average crown spread of 68.00' (180 points) (Rouw, M., personal communication, 8 February 2021). | 1940580 | Ames 33357 |