In 1999, LSU Agricultural Center landscape trials of herbaceous ornamental plants included zinnias, ornamental sweet potatoes, vinca, and perennial verbenas. Based on growth habit, flowering and disease observations from 1999 and previous years, `Homestead Purple', `Tiger Rose', `Rose King', `Taylortown Red', and `Blue Princess' (`Biloxi Blue') are recommended perennial verbena cultivars for Louisiana landscapes. Zinnias evaluated included Zinnia angustifolia and Z. elegans cultivars. `Crystal White', `Profusion Orange', and `Profusion Cherry' (all Z. angustifolia cultivars) were superior landscape performers. Major incidence of bacterial leaf spot was reported on all Z. elegans cultivars in 1999. Over the last several years, the Pacifica series of vinca had significantly improved visual quality ratings in landscape trials when compared to the Heat Wave and Cooler series. In 1999, Mediterranean Deep Rose had visual quality ratings similar to Pacifica but had increased incidence of disease problems. Ornamental sweet potato cultivars recommended for landscape use in Louisiana based on trials in 1999 are `Blackie', `Black Beauty', `Margarite', and `Pink Frost' (`Tricolor'). `Summer Frost' is not recommended.
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