Grand Duke (syn. Grossherzog's Pflaume & Grand-Due) is a variety of plum, one of the so-called European plums. Note that this journal predates the 2011 International Botanical Congress which determined that the combined subfamily, referred to in this article as Spiraeoideae, should be called Amygdaloideae It is one of the many plums produced by Thomas Rivers of Sawbridgeworth, England. The Royal Horticultural Society awarded it a First Class Certificate in 1880. The fruit has a fairly firm, rather dry flesh with a slightly tart to slightly sweet flavor. It can tolerate USDA hardiness zones 5b, 5a, 6b, 6a, 7b, and 7a.
References