NEW NONINVASIVE VARIETIES OF INVASIVE ORNAMENTALS by Larry Williams, UF/IFAS Extension Agent

Some non-native plants are invasive in Florida. Kudzu and Chinese tallow (popcorn tree) are two of the more common examples.  Gary Knox, UF/IFAS Extension horticulturist, encourages home gardeners to look for noninvasive types of invasive landscape plants in this installment.

Chinese privet was grown as a shrub or hedge plant in urban landscapes but now is found throughout Florida’s forested areas. Unfortunately, many other non-native ornamentals have been implicated as invasive. The invasiveness of these non-natives was based on the wild form of the plant first introduced/used as an ornamental decades ago. Today, gardeners can grow cultivars or varieties of these invasive non-natives, some of which differ radically from their wild form. Fortunately, University of Florida researchers are finding that some varieties of invasive ornamentals are sterile or produce few seed.

Nandina (Nandina domestica) is one of the invasive ornamentals being studied. Nandina is a popular landscape plant. Introduced to the US before 1804, the wild type of the species has since escaped cultivation in nine states including Florida. Currently, the wild type is not widely grown, but dwarf cultivars are primarily grown by nurseries and planted by landscapers and gardeners. Our research found wide variation in growth and fruiting among nandina cultivars and regions of Florida, and several are virtually fruitless in parts or all of Florida. This research validates the importance of research to assess cultivars of ornamentals for invasiveness and indicates ornamentals should be trialed in various regions to assess invasiveness in each region.

Our research found nandina cultivars “firepower,” “Gulf Stream” and “Harbour Dwarf” are virtually noninvasive and can be grown safely throughout Floria, though gardeners should watch for occasional escaped seedlings. Additionally, Harbor Belle nandina might be grown safely in South Florida. Our previous research verified that the species and all varieties of Japanese silver-grass (Miscanthus sinensis) and butterflybush (Buddleja lindleyana) and (B. officinalis) are not invasive in Florida. Gardeners can safely grow these without risk of unleashing more invasive plants into natural areas.

Our research found varieties of fountaingrass (Pennisetum spp.), Mexican petunia (Ruellia tweediana) and porterweed (Stachytarpheta spp.) that are noninvasive. These results are undergoing an evaluation process to be validated as such by UF/IFAS

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