 'Plantyn' is no more resistant to Dutch elm disease than its Dutch contemporaries 'Dodoens' and 'Lobel' according to one source, rating 4 out of 5.However, research published in France by the Institut National de la Recherche Agronomique (INRA) indicated that 'Plantyn' possesses a greater degree of disease resistance than the other two cultivars, although neither had actually been tested by the organization.Nevertheless, INRA still classified 'Plantyn' as only 'moderately resistant'.