[[(U. pumila x (U. x hollandica “Vegeta” x U. minor))] x [U. davidiana var. Japonica]]
United States National Arboretum
Patriot arose from Alden Townsend’s 1980 crossing of the clone “Urban” (itself a hybrid of Siberian elm with a “Vegeta” (Huntingdon) and field elm cross) with a selection of Japanese elm later named “Prospector”. The tree was released in 1993, free of patent restrictions, and was introduced into Britain some 15 years later.
Patriot was included in inoculation trials carried out on two dates in May 1992. Wilting, observed four weeks later, ranged from 11% from the earlier inoculation to 6% for the later one. Dieback, observed a year later, was given as 1%.
These results suggest very good resistance, and there are no reports of Patriot contracting elm disease. However, doubts have recently surfaced with regard to some US inoculation testing after the U. americana clone “Princeton” began to succumb to disease despite scoring highly in trials. Patriot will therefore be assessed again in France in 2014, and probably also in the Netherlands within the next few years.
Patriot is monopodial when well grown, and highly vigorous. Its habit seems to vary considerably. It is capable of stiffly upright growth, strongly reminiscent of some strains of U. minor in south east England, but in some conditions its branching is far more lax. Erect growth may be linked to optimal root development; certainly it is most lacking in specimens which have become pot-bound.
The tree’s vigour was amply demonstrated by a one year old whip received in 2010 which increased in height by 250cm in its second year. Girth increment is very slow by comparison, leading to major problems of stability. Successive transplantations and heading back of leaders may go some way to addressing this problem.
Patriot leaves are fairly glossy, only slightly toothed and veination is pronounced. The margin tends to undulate, and the leaf often folds upwards as the season progresses. Leaf stalks are relatively long. In these respects the tree’s Asian genes are predominant. Similarities to European field elm are the fresh green of the spring foliage, steadily darkening into summer, and the burnt gold autumn colouration.
Patriot enters into flower at the age of four to five years. Flowers may appear as early as January and open in the first week of February. However, the setting and maturation of seed seems heavily dependent on weather conditions.
Softwood cuttings may be taken in mid-May, using vigorously growing shoots from near the tips of branches or side shoots from very young plants. Rooting occurs within four to five weeks, and strike rate can be in excess of 90%.
Patriot’s monopodial growth, vigour, ease of propagation, general appearance and likely size at maturity make it impossible to overlook. Presumably the problem of balance between height and girth increments can be substantially mitigated as the tree’s requirements become better understood over time. It is to be hoped that the disease resistance shown in US trials will be confirmed by the forthcoming European testing. Nevertheless, a final issue relates to the clone’s female parent, Urban. This tree proved susceptible to Nectria cinnabarina, the cause of various cankers including coral spot. There are no reports that Patriot has inherited this vulnerability, but personal observation raises a doubt.