Ulmus minor 'Ademuz'


The Field Elm cultivar Ulmus minor 'Ademuz' was cloned by root cuttings from a tree growing near the eponymous town north-west of Valencia, Spain, discovered in 1996 by the late Margarita Burón of the Escuela Técnica Superior de Ingenieros de Montes, Universidad Politėcnica de Madrid. The tree 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'. In the Madrid study, the appearance of the tree was rated 4.5 / 5, the most attractive of the selected cultivars.
'Ademuz' was introduced to the UK in 2014, 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.

Description

'Ademuz' grew at 100 cm per annum, the fastest of the U. minor clones under assessment at Puerta de Hierro, Madrid. The tree is often monopodial, its branches devoid of corky tissue. The leaves, on 5 mm petioles, are ovate, typically acuminate at the apex, the average length and width 54 × 34 mm, the margins doubly serrate. Foliar density relative to 'Sapporo Autumn Gold' is described as 'medium'.
DNA analysis by UPM in 2019 has confirmed that 'Ademuz' is pure Ulmus minor.

Pests and diseases

In inoculation trials conducted in 2008, 'Ademuz' sustained approximately 10% damage against a score of c. 45% for the benchmark-resistant cultivar 'Sapporo Autumn Gold'. In 2009 'Ademuz' scored c. 18%, and Sapporo c. 21%. Ergo, 'Ademuz' would appear to have a level of resistance unprecedented in a European species. However in Italian elm trials, some Spanish U. minor clones have shewn a greater susceptibility to elm yellows, a phytoplasma not known in either the UK or Spain, than those of any other provenance. Whether 'Ademuz' shares this susceptibility has yet to be established.

Cultivation

The location of the parent tree is not known but believed to be near the eponymous town on the outskirts of Valencia. The climate of Valencia is typically dry and frost-free, with an annual average rainfall total of @450 mm, the majority falling in autumn. Rainfall from January is about 30-40 mm per month until July, when it falls to @10 mm.
'Ademuz' has also thrived at four sites in Hampshire, England, as part of Butterfly Conservation's elm trials, where the rainfall is approximately double the Valencia total, and geology ranges from chalk to impermeable clays. However, it has made minimal growth on marshy ground, where the predominant vegetation is Hemlock Water Dropwort Oenanthe crocata. 'Ademuz' has proven particularly resilient where exposed to sea winds, notably where grown on Horsea Island in Portsmouth Harbour, Hampshire.

Etymology

'Ademuz' is derived from the Arabic 'Ad-damus', which appears to mean 'impregnable', and the origin of the English words 'adamant' and 'diamond'.

Accessions

;Europe