Radicchio (Cichorium intybus var. latifolium) is grown widely throughout Europe, especially northern Italy. This crop features several groups that differ in color, shape, and culinary use, and there is considerable phenotypic variation among and within groups and cultivars. The New England growing climate is very different from that of major production regions in Europe and the pacific northwestern U.S. The availability of varieties to commercial growers in the U.S. has expanded greatly, but there remains a need for regionally relevant information about performance of these varieties. In Durham, NH, USA we grew 30 (2022) and 34 (2023) cultivars of radicchio belonging to seven main groups (Chioggia, Castelfranco, Treviso, Sugarloaf, Verona, Rosa del Veneto, and Lusia). In both years, they were seeded on 20-21 June, and transplanted on 14-15 July. Plants were harvested and weighed as they reached market maturity, or considered unmarketable due to bolting, rot, tipburn, or failure to head. We used standard cultural practices for the region: plants were grown in double rows on 30-inch-wide raised beds covered with white-on-black plastic mulch with drip irrigation. The weather in 2022 and 2023 differed greatly, with 2022 experiencing warm and dry conditions, and 2023 much wetter and cooler. The percentage of heads that became marketable ranged from 0-94% in 2022, and from 10-95% in 2023. Several cultivars had very high percentages of unmarketable heads, due to tipburn, rot, bolting, or failure to head. We also observed cultivar differences in susceptibility to powdery mildew. In both years, the cv. Rubro developed powdery mildew early and developed severe symptoms, several others eventually developed symptoms, and some never did. For traditional round red Chioggia types, several cultivars had very high percentages of marketable heads, and appear to be well adapted to production in the northeast. We identified cultivars within both sugarloaf and Treviso types that were well adapted, with high percentages of marketable heads. The cultivars we evaluated within the Lusia and Rosa del Veneto types were especially interesting from a culinary and attractiveness point of view, but had high percentages of rot (Lusia types) and very long days to maturity required (Rosa del Veneto types).
