Ulmus laciniata var. nikkoensis

Ulmus laciniata var. nikkoensis Rehder, the Nikko elm, was discovered as a seedling near Lake Chūzenji, near Nikkō, Japan, and obtained by the Arnold Arboretum in 1905.[1] The taxonomy of the tree remains a matter of contention, and has been considered possibly a hybrid of U. laciniata and U. davidiana var. japonica. However, in crossability experiments at the Arnold Arboretum in the 1970s, U. laciniata, a protogynous species, was found to be incompatible with U. davidiana var. japonica, which is protandrous.[2]

Ulmus laciniata var. nikkoensis
Nikko Elm at the Morton Arboretum
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Rosales
Family: Ulmaceae
Genus: Ulmus
Species:
Variety:
U. l. var. nikkoensis
Trinomial name
Ulmus laciniata var. nikkoensis

Significantly, the variety was not recognized by Ohwi,[3] though his reasons are not clear. Kew's 'Plants of the World Online' treats var. nikkoensis as a synonym of U. laciniata.[4]

Description

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Var. nikkoensis is a small tree; the specimen at the Morton Arboretum likened to a cherry tree.[5] The tree is chiefly distinguished by leaves which are red on emergence, and toothed but not lobed as in the species.[6] The perfect apetalous wind-pollinated flowers appear in March in England.

Pests and diseases

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Heybroek found the tree provided 'relatively resistant' (to DED) progeny in the Dutch elm breeding programme.[1]

Cultivation

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There are no known cultivars of this taxon, nor is it known to be in commerce beyond the United States.

Etymology

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Var. nikkoensis is named for the Nikkō National Park near the city of Nikkō, 125 km north of Tokyo.

Accessions

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North America
Europe

Putative specimens

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Trees at Great Fontley, Fareham, in southern England, grown from seed sent from Morton Arboretum and reputedly sourced in Liaoning Province, China, that were thought for many years to be Ulmus davidiana, have fruit and short petioles inconsistent with that species, but matching descriptions and photographs of Ulmus laciniata. Their leaves, to date (2023) lacking long extra tips, recall those of var. nikkoensis.[9] In trials conducted by Butterfly Conservation, the specimens at Great Fontley often grew too rapidly in the comparatively benign conditions, the narrow stem unable to bear the weight of the burgeoning crown, leaving the tree arching to the ground. The same trees commenced flowering when aged nine years, in mid-March.[10] They were defoliated at the crown by DED when only 6 years old and < 4 m (13 ft) high, but recovered. They were, however, heavily afflicted by slime flux during the exceptional drought of summer 2022; the only elm at Great Fontley to be so.[10]

References

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  1. ^ a b Heybroek, Hans M. (1981). "The Japanese elm species and their value for the Dutch elm breeding program" (PDF). Proceedings of the Dutch Elm Disease Symposium and Workshop, October 5–9, Winnipeg, Manitoba: 78–90.
  2. ^ Hans, A. S. (1981). "Compatibility and Crossability Studies in Ulmus". Silvae Genetica. 30: 4–5.
  3. ^ J, Ohwi (1965). Flora of Japan. Smithsonian Institution. ISBN 9781139428651.
  4. ^ Ulmus laciniata (Herder) Mayr ex. Schwapp; RBG Kew, Plants of the World Online, powo.science.kew
  5. ^ J., Grimshaw; Bayton, R. (2009). New Trees - Recent Introductions to Cultivation. Royal Botanic Gardens, Kew, London. ISBN 978-1842461730.
  6. ^ Harvard University Herbaria & Libraries: herbarium specimen 00034309 Ulmus laciniata var. nikkoensis Rehder, Alfred Rehder specimen (Arnold Arboretum), 1924
  7. ^ "Collectionsgarden_Plant Search". Archived from the original on October 25, 2007.
  8. ^ "Nikko Elm - Ulmus laciniata var. 'nikkoensis'".
  9. ^ Brookes, A. H. (2020). Great Fontley Elm Trial, 2020 Report. Butterfly Conservation, Lulworth, England.
  10. ^ a b Brookes, A. H. (2022). Great Fontley Elm Trial, 2022 Report. Butterfly Conservation, Lulworth, England.