Ulmus × intermedia

Ulmus × intermedia Elowsky is a natural hybrid elm occurring across Nebraska and several other Midwestern states, derived from the crossing of Ulmus rubra and Ulmus pumila.[1] As Red Elm U. rubra is far less fertile, and highly susceptible to Dutch elm disease (:DED), it could eventually be hybridized out of existence by U. × intermedia.[2] The hybrid was first reported from the wild in the Chicago region in 1950 and was provisionally named U. × notha Wilhelm & Ware in 1994.[3]

Ulmus × intermedia
Hybrid parentageU. pumila × U. rubra
OriginUS

The horticulture industry made a number of artificial crosses of the two species, such as 'Coolshade' and 'Fremont', in an attempt to create ornamental trees resistant to DED.[1]

Description

Ulmus × intermedia is significantly different from both parental species, except in biometrics such as leaf length to width ratios, number of teeth, petiole length, and pollen size. The leaves are 4.5–12 × 2.5–6  cm, petiole 0.3 × 1.2  cm, ovate to lanceolate, apex acuminate to acute, base oblique. The samarae are 11.5–21.0 × 10.0–20.0 mm, cream to white.[1] Atypically, fertility of the hybrid seed is high, occasionally in excess of 90%,[4] while Collins found in artificial hybridization no reduction of fertility in the F1 or F2 generations.[5]

Pests and diseases

Morton Arboretum report the hybrid susceptible to DED and Elm Yellows (Elm phloem necrosis).[6]

Cultivation

Specimens of unnamed Ulmus × intermedia ( = Ulmus × notha) stand (2015) in Morton Arboretum, Illinois, received as Ulmus pumila from North Platte Agricultural Experiment Station, University of Nebraska.[7][8][6]

Cultivars

References
  1. Elowsky, C.G.; Jordon-Thaden, I.E.; Kaul, R.B. (10 July 2013). "A morphological analysis of a hybrid swarm of native Ulmus rubra Muhl. and introduced U. pumila L. (Ulmaceae) in southeastern Nebraska" (PDF). Phytoneuron. 2013–44: 1–23. ISSN 2153-733X. Retrieved 25 October 2017.
  2. Schlautman, B., Zalapa, J., & Brunet, J. (2012). Genotypic and phenotypic characterization of Ulmus pumila (Siberian elm), Ulmus rubra (Red elm) and their hybrids. Proc. Nebraska Acad. Sci. 2012. 106–107.
  3. Swink, Floyd; Wilhelm, Gerould (1994). Plants of the Chicago Region (4 ed.). Indianapolis: Indiana Academy of Sciences. p. 761. ISBN 9781883362010. Retrieved 25 October 2017.
  4. Kaul, R. B. (1995). Natural and fertile hybrids of the native red elm, Ulmus rubra, with the introduced Siberian elm, U. pumila, are now producing hybrid swarms in Nebraska. Proc. Nebraska Acad. Sci. 105: 28–29.
  5. Collins, P. E. (1967). Hybridization studies in the genus Ulmus. Ph.D dissertation, Univ. of Minnesota, Minneapolis.
  6. U. × notha, Morton Arboretum , vplants.org
  7. Unnamed Ulmus × intermedia, quercus.mortonarb.org
  8. Photographs of Ulmus × intermedia, Morton Arboretum, 'Ulmus Series', acorn.mortonarb.org
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.