Winter-hardiness of 52 cultivars of Hibiscus syriacus trees was investigated at Suwon for the winter of 1970-1971. The cultivars which investigated in the present studies were imported at the United States National Arboretum, Botanic Garden of Osaka City University, Los Angeles State & County Arboretum, The Wayside Gardens Co., and Gulf stream Nursery Inc.
Winter-Hardiness test was conducted for 1-year seedlings without the cold protecting measures. Nearly all the cultivars examined were well overwintered, and if the trees were grown for the successive year with cold protecting measures, and were grown to aged trees, one can expect that many cultivars of this plant are supposed to grow well in Korean environments without cold protecting measures.
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