Ulmus minor 'Retiro'
The Field Elm cultivar Ulmus minor 'Retiro' was raised from seed collected in 2002 from a tree growing in the El Retiro park (40°24′56″N 3°41′10″W),[1] in the centre of Madrid by researchers at the Escuela Técnica Superior de Ingenieros de Montes, Universidad Politėcnica de Madrid. [1]
| Ulmus minor 'Retiro' | |
|---|---|
 'Retiro' | |
| Species | Ulmus minor |
| Cultivar | 'Retiro' |
| Origin | Spain |
'Retiro' was introduced to the UK in 2015, by Hampshire & Isle of Wight Branch, Butterfly Conservation, as part of an assessment of DED-resistant cultivars as potential hosts of the endangered White-letter Hairstreak.[2]
Description
'Retiro' grew at a comparatively modest rate of 70 cm per annum in the trials at Puerta de Hierro, Madrid. The erect branches, devoid of corky tissue, form a globular crown. The leaves, on 7 mm petioles, are elliptic, typically acuminate at the apex, the average length and width 71 × 42 mm, the margins doubly serrate. Foliar density relative to 'Sapporo Autumn Gold' is described as 'high'. In the Madrid study, the appearance of the tree was rated 4 / 5. [1]
'Retiro' leaf
'Retiro' sapling, with typical arching stem
Pests and diseases
'Retiro' is one of a number found to have a very high resistance to Dutch Elm Disease, on a par with, if not greater than, the hybrid cultivar 'Sapporo Autumn Gold'.[1]
Cultivation
The cultivar is (2018) undergoing further trials in a different environment in Spain, where it was tested by inoculation in 2016. If resistance is still considered satisfactory, the tree will be released to commerce under licence. 'Retiro' is also being assessed as part of Butterfly Conservation's elm trials in southern Hampshire, England.[2]
Accessions
Europe
- Grange Farm Arboretum, Lincolnshire, UK. Acc. no. 1269.
- Great Fontley Butterfly Conservation Elm Trials plantation, UK. One sapling planted 2015.
References
- Martín, JA; Solla, A; Venturas, M; Collada, C; Domínguez, J; Miranda, E; Fuentes, P; Burón, M; Iglesias, S; Gil, L (2015-04-01). "Seven Ulmus minor clones tolerant to Ophiostoma novo-ulmi registered as forest reproductive material in Spain". IForest - Biogeosciences and Forestry. Italian Society of Sivilculture and Forest Ecology (SISEF). 8 (2): 172–180. doi:10.3832/ifor1224-008. ISSN 1971-7458.
- Brookes, A. H. (2020). Great Fontley Elm Trial, 2020 Report. Butterfly Conservation, Lulworth, England.