[[((U. wallichiana x U. minor) x (U. pumila x U. minor)) o.p.] x (U. x hollandica “Vegeta” x U. minor)] o.p.
Istituto per la Protezione delle Piante, Florence, Italy
This is a complex hybrid, in essence three quarters European elm, one eighth Himalayan elm and one eighth Siberian elm. Of the European genetic inheritance one eighth is x Vegeta (Huntingdon elm), and that is the character which seems to be predominant. FL 493 was introduced into Britain in spring 2013 with the gift of ten plants from the IPP.
In inoculation trials conducted in Antella, Florence, in 2000, FL 493 exhibited defoliation of only 1.44%, and dieback of 0%. This degree of resistance has been bettered by only one or two other hybrids, and appears to amount to virtual immunity (by way of comparison, data for the highly resistant “Sapporo Autumn Gold” are 2.78% and 1.22% respectively).
FL 493, seen at the Castellaccio adaptation trials site in 2010, was reminiscent of the Dutch/French clone “Lutece”, with which it shares some U. wallichiana ancestry. Given the strong x Vegeta (Huntingdon) character of the foliage, it may be that the tree itself will develop into the ascending vase shape of Huntingdon Elm with time. Between 2001 and 2009 at Castellaccio the plant averaged an impressive annual height increment of 194cm, well balanced by a girth increment of 2.84cm.
At a suburban amenity planting on the outskirts of Florence, the one specimen seen in 2010 had an amorphous and congested habit. However, the same was true of several other elm clones in that environment, and may reflect local climatic and/or soil conditions. More specimens were seen in September 2013, and were impressive in all respects (See photo to right).
Leaves on non-vigorous shoots in spring are fresh green and indistinguishable from strains of European elm. Certain leaves on vigorous shoots show some pumila (Siberian) character. Flushing is synchronic with English elm. Foliage at Castellaccio in September 2010 was mid green, and similar in size, shape and colour to Huntingdon. However, a plant kept in an unheated conservatory in the early spring of 2013 and later placed outside abruptly developed dark malachite colouration, possibly as a result of the fall in temperature. It lightened again at the end of the summer.
The exemplary disease resistance of FL 493 in combination with its vigour and balance give it obvious potential. Its final form of growth is not fully apparent yet and may be less than perfect, but at present this tree seems the best produced by any of the Elm breeding programmes.
Wikipedia reference: n/a