Roses are popular landscape plants valued for their beautiful and diverse floral displays that can be enjoyed throughout the majority of the growing season. Most of the landscape rose cultivars available today are not reliably winter hardy in U.S. Department of Agriculture (USDA) Plant Hardiness Zones 3 and 4 (USDA Plant Hardiness Zone Map, 2012). Susceptibility to rose black spot (Diplocarpon rosae F.A. Wolf) and other foliar diseases such as spot anthracnose [Sphaceloma rosarum (Pass.) Jenk.] is also a limiting factor. Foliar diseases defoliate plants and reduce the ornamental value, vigor, and winter survival of susceptible cultivars. A breeding program was initiated at the University of Minnesota in 1990 to develop cold-hardy, repeat blooming, black spot–resistant landscape rose cultivars available for use in northern continental landscapes (Zuzek and Hokanson, 2007). Below we describe four polyantha rose cultivars developed by the Woody Landscape Plant Breeding and Genetics Project at the University of Minnesota.
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