The winter hardiness of many groundcover cultivars in northern Illinois is not well-known. This study was designed to evaluate the survival of 172 plants used in the groundcover path at The Morton Arboretum. Once a month, from Sept.1997 to Jan. 1998, the plants chosen for this study were visually evaluated and their vitality rated on a scale of 1 to 5 (1 = alive, 5 = dead). All nine cultivars of Euonymus fortunei remained virtually unchanged throughout the study period. Among six cultivars of Hedera helix, only `Gold Heart' showed minor damage in November. Nine Heuchera were evaluated and all exhibited excellent resistance to cold temperatures. While all the Pulmonarias studied showed some cold damage by November, `Bielefeld Pink', `Little Blue', `Roy Davidson', Pulmonaria longifolia var. cevennensis, and Pulmonaria officinalis `Sissinghurst White' fared the best for the longest period of time. Five cultivars of Pachysandra terminalis were included in this study. None had significant damage until November, and then only rated a “2.” Of the eight Ajuga evaluated, Ajuga pyramidalis `Metallica Crispa', and Ajuga reptans `Braunherz', `Catlin's Giant', and `Gaiety', exhibited the best cold resistance. Four Polygonums varied widely in their response to cold temperatures, but all showed signs of severe damage in November. Polygonum `Border Jewel' exhibited the best tolerance, rating a “1” in October, but in November it was given a rating of “4.” Their recovery in spring will be compared.
