ADRIENNE SMITH Mexican- invasion at Lake Jesup Conservation Area (Sanford, FL). Mexican-petunia () Invasions: Management Challenges and Research Opportunities By Adrienne M. Smith, Carrie Reinhardt Adams, and Sandra B. Wilson

exican-petunia (Ruellia simplex), South Florida due to its invasiveness known for its prolific purple and rapid spread in these regions (IFAS Mflowering in a range of Invasive Working Group 2013). conditions, is a commonly planted It has been shown that Mexican- herbaceous perennial used in many petunia has a competitive advantage landscape settings. Native to Mexico over the native Carolina wild-petunia and South America, Mexican-petunia () for resource was presumably introduced as an utilization and efficiency (Wilson et al. ornamental (Bailey and Bailey 1976). 2004). In addition, Mexican-petunia It was first noticed as naturalized along seeds germinate readily under a range the Florida through Louisiana coast- of temperature and light conditions lines in 1933 (Small 1933). Presently, (Wilson and Mecca 2003). In natural this species is invading natural areas areas, Mexican-petunia propagules throughout the southeastern United often travel through stormwater runoff States (EDDMapS 2013), including deposited in floodplain forests. Upon 29 counties in Florida (Wunderlin germination and establishment in Mexican petunia invasions: EDDMapS (2014) and Hansen 2012) (Figure 1). In these floodplains, Mexican-petunia County boundaries: University of Florida GeoPlan Center 1:3,600,000 (2011) Florida, Mexican-petunia was first increases in abundance and ultimately listed in 1999 as a Florida Exotic Pest dominates the aboveground cover, Figure 1. Documented invasions of Mexican Plant Council (FLEPPC) Category II creating monotypic invasions (Figures petunia in Florida (EDDMapS 2014). Invasive (classified as increasing in 2a and 2b). Continued propagule intro- abundance but not displacing native duction into floodplains contributes to The same plant characteristics that plant communities). In 2001, it was the capacity for Mexican-petunia to are desirable for the ornamental market promoted to a FLEPPC Category I alter ecosystem processes and success- of often increase the prob- Invasive as displacement of native plant fully compete with native species for ability for invasion (repeat blooming, communities by Mexican-petunia was available resources (Gordon 1998; low maintenance, wide adaptability, recurrently observed (FLEPPC 2011). Mack et al. 2000). Control of exist- ease of propagation, stress tolerance, In addition to its FLEPPC ranking, the ing propagule sources (i.e. seed from short juvenile period, consumer UF/IFAS Assessment does not recom- surrounding landscapes) is required to demand) (Wirth et al. 2004; Drew et mend its use for North, Central, and limit invasions. al. 2010). Since Mexican-petunia is

20 SPRING 2014 an ornamental invasive that is still in commercial production, it presents unique challenges as future invasions and reinvasions are likely. A number of cultivars of Mexican-petunia are avail- able commercially and most are fertile (Wilson and Mecca, 2003; Hupp et al. 2009). The University of Florida Orna- mental Breeding Program (Gainesville, FL) has recently released two sterile cultivars as alternatives for growers and homeowners (Freyre et al. 2012; Freyre et al. 2013). A second approach to reducing propagule pressure of invasives is to suggest the use of native species that have similar ornamental ADRIENNE SMITH value (Wilson et al. 2009). Figure 2a. Mexican-petunia invasion at Hogtown Creek (Gainesville, FL). Initial control of Mexican- petunia is relatively straightforward. Planting native species for control of varying light and temperature regimes Experiments for developing control invasive species may be particularly to compare the rate of germination of methods for Mexican-petunia tested important in landscapes where rein- these natives compared to Mexican- four readily available herbicides and vasion is likely; for example, if the petunia. Natives had a slower germi- found that glyphosate effectively invasive plant is ornamental and still nation rate than Mexican-petunia reduced Mexican-petunia cover (R. in commercial production. As noted (data not presented). For an effective Stocker, personal communication; by Adams et al. (2013), the next revegetation strategy, this suggests Wiese et al. 2013). Adams et al. step in management is to determine the potential need for sowing natives (2013) further examined the effect and possible mechanisms that prevent at higher densities to compensate for number of glyphosate applications on native species establishment. Current the slower germination, thus allowing Mexican-petunia when sprays were research is underway for 1) determin- them to better establish and suppress initiated in the fall or spring. Sixty to ing revegetation methodology, and 2) Mexican-petunia. Current research is seventy percent reductions in cover of determining abiotic factors that may in progress to test this theory, both in Mexican-petunia resulted, regardless promote Mexican-petunia dominance. greenhouse competition studies and of the number of applications and While active revegetation is field studies (conducted at the Lake application season, thus concluding commonly needed to fully restore Jesup Conservation Area). that a single glyphosate application in the native plant community follow- Another barrier to Mexican- the fall or spring is sufficient to control ing invasive species control, specific petunia control and native species Mexican-petunia (Adams et al. 2013). strategies for revegetation are limited. establishment may be related to Effective control and management Determining which natives are plant-soil interactions. Monotypic of invasive plants is critical to restora- appropriate for revegetation is one invasions are commonly characterized tion of degraded urban lands, yet in of the first steps. Appropriate criteria by having little to no other species some cases, relying on natural recolo- are presented in Table 1. We applied (native or invasive/exotic) present in nization of native species after initial these criteria to identify candidate the aboveground cover (Eliason and control is not sufficient (Kettenring native species for active revegetation Allen 1997; Brewer 2008; Spyreas et and Adams 2011). Planting natives of managed Mexican-petunia flood- al. 2010). Despite our observations for revegetation has been shown to plain sites. Using a broad survey of of bare ground that should represent facilitate restoration of the native plant vendors with seed availability, the microsites for other species to estab- community and simultaneously limit candidate list was narrowed to the lish, there are no co-occurring species reinvasion (Blumenthal et al. 2003). following 4 species: bushy bluestem within Mexican-petunia invasions. This has been well-demonstrated (Andropogon glomeratus), soft rush The lack of additional species in the for prairie vegetation (Blumenthal (Juncus effusus), redtop panicgrass cover is particularly unexpected, et al. 2003) and has shown promise (Panicum longifolium), and pinebarren especially given the native species in wetlands, but research is lack- goldenrod (Solidago fistulosa). Germi- detected in the seedbank beneath ing (Kettenring and Adams 2011). nation studies were conducted under Mexican-petunia invasions. In fact,

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References

Adams, C., C. Wiese, and L. C. Cobb. 2013. Effect of season and number of glyphosate applications on control of invasive Ruellia simplex. Ecological Restoration. Submitted.

Bailey, L. H., and E. Z. Bailey. 1947. Hortus Second. Macmillian Co., New York.

Blumenthal, D. M., N. R. Jordan, and E. L. Svenson. 2003. Weed control as a rationale for restoration: The example of tallgrass prairie. Conservation Ecology 7:6.

Brewer, S. 2008. Declines in plant species richness and endemic plant species in longleaf pine savannas invaded by Imperata cylindrica. Biological Invasions 10:1257-1264.

Brown, C. S., V. J. Anderson, V. P. Claassen, M. E. Stannard, L. M. Wilson, S. Y. Atkinson, J. E. Bromberg, T. A. Grant, and M. D. Munis. 2008. Restoration Ecology and Invasive Plants in the Semiarid West. Invasive Plant Science and Management 1:399-413.

Corr, K., comp. 2003. Revegetation techniques: a guide for establishing native vegetation in Victoria. Greening Australia Victoria, Australia. 131 pp.

Drew, J., N. Anderson, and D. Andow. 2010. Conundrums of a complex vector for invasive species control: a detailed examination of the horticultural industry. Biological Invasions 12:2837-2851.

EDDMapS. 2013. Early Detection & Distribution Mapping System. The University of Georgia, Center for Invasive Species and Ecosystem Health. URL http://www.eddmaps.org/ [accessed on 22 August 2013]

Eliason, S. A., and E. B. Allen. 1997. Exotic grass competition in suppressing native shrubland re- establishment. Restoration Ecology 5:245-255.

Fischenich, J. C. 2001. Plant material acquisition and handling. ERDC TN-EMRRP-SR-33. United States Army Engineer Research and Development Center, Vicksburg, Mississippi.

Florida Exotic Pest Plant Council (FLEPPC). 2011. List of Invasive Plant Species. URL http://www.fleppc.org/list/11list.htm [accessed on 2 November 2012]

Freyre, R., A. Moseley, S. B. Wilson, and G. W. Knox. 2012. Fruitless Ruellia simplex R10-102 (‘Mayan Purple’) and R10-108 (‘Mayan White’). HortScience 47:1808-1814.

Freyre R., A. Moseley, C. Reinhardt-Adams, A. G. W. Knox, S. B. Wilson, and Z. Deng. 2013. Breeding Ruellia spp. at the University of Florida. Proceedings of the VIIth International Symposium on New Floricultural Crops. G. Facciuto and M.I. Sanchez, Eds. Acta Horticulturae1000, pp. 423-428.

Garbisch E. W. 1986. Highways and wetlands: Compensating wetland losses. Contract Report DOT-FH-11-9442. Federal Highway Administration, Office of Implementation, McLean, Virginia.

WILDLAND WEEDS | SPRING 2014 | ONLINE SUPPLEMENT TO INCLUDE REFERENCES

Goosem, S. P., and N. I. J. Tucker. 1995. Repairing the rainforest: theory and practice of rainforest re-establishment in North Queensland's wet tropics. Wet Tropics Management Authority, Cairns, Australia.

Gordon, D. R. 1998. Effects of invasive, non-indigenous plant species on ecosystem processes: Lessons from Florida. Ecological Applications 8:975-989.

Hupp, K. V. S., A. M. Fox, S. B. Wilson, E. L. Barnett, and R. K. Stocker. 2009. Natural area weeds: Mexican petunia (Ruellia tweediana). ENH1155. Institute of Food and Agricultural Sciences, University of Florida.

Invasive Plant Working Group. 2013. IFAS assessment of non-native plants in Florida’s natural areas: Conclusions. URL http://plants.ifas.ufl.edu/assessment/pdfs/status_assessment.pdf [accessed on 23 August 2013]

Kettenring, K. M., and C. R. Adams. 2011. Lessons learned from invasive plant control experiments: a systematic review and meta-analysis. Journal of Applied Ecology 48:970-979.

Kettenring, K. M., K. L. Mercer, C. R. Adams, and J. Hines. 2013. Application of genetic diversity- ecosystem function research to ecological restoration. Journal of Applied Ecology. In review.

Mack, R. N., D. Simberloff, W. M. Lonsdale, H. Evans, M. Clout, and F. A. Bazzaz. 2000. Biotic invasions: Causes, epidemiology, global consequences, and control. Ecological Applications 10:689- 710.

Mazzota, W., C. R. Adams, and C. Wiese. 2012. Comparing floodplain forest vegetation dynamics in Ruellia simplex (Syn. R. tweediana; Mexican petunia) invaded and non-invaded land using a seed bank study. University of Florida Undergraduate Research Conference. Gainesville, FL.

McClain, C. D., K. D. Holl, and D. M. Wood. 2011. Successional models as guides for restoration of riparian forest understory. Restoration Ecology 19:280-289.

Sheley, R. L., P. B. Hook, and R. R. Lecain. 2006. Establishment of native and invasive plants along a rangeland riparian gradient. Ecological Restoration 24:173-181.

Small, J. K. 1933. Manual of the southeastern flora, part one and two. University of North Carolina Press, Chapel Hill.

Spyreas, G., B. W. Wilm, A. E. Plocher, D. M. Ketzner, J. W. Matthews, J. L. Ellis, and E. J. Heske. 2010. Biological consequences of invasion by reed canary grass (Phalaris arundinacea). Biological Invasions 12:1253-1267.

Stark, N. 1972. Low maintenance vegetation – Wildland shrubs, their biology and utilization. General Technical Report INT-1. United States Department of Agriculture, Forest Service, Washington, D.C.

White, P. S., and J. L. Walker. 1997. Approximating nature's variation: Selecting and using reference information in restoration ecology. Restoration Ecology 5:338-349.

WILDLAND WEEDS | SPRING 2014 | ONLINE SUPPLEMENT TO INCLUDE REFERENCES

Wiese, C., C. R. Adams, and A. M. Smith. 2013. Experimental research informs control of Mexican petunia (Ruellia simplex) in natural areas and home-gardens. Proceedings of the Florida State Horticultural Society. Submitted.

Wilson, S. B., and L. K. Mecca. 2003. Seed production and germination of eight cultivars and the wild type of Ruellia tweediana: A potentially invasive ornamental. Journal of Environmental Horticulture 21:137-143.

Wilson, S. B., G. W. Knox, K. L. Muller, R. Freyre, and Z. Deng 2009. Seed production and viability of eight porterweed selections grown in northern and southern Florida. Hortscience 44:1842-1849.

Wilson, S. B., P. C. Wilson, and J. A. Albano. 2004. Growth and development of the native Ruellia caroliniensis and invasive Ruellia tweediana. Hortscience 39:1015-1019.

Wirth, F. F., K. J. Davis, and S. B. Wilson. 2004. Florida nursery sales and economic impacts of 14 potentially invasive landscape plant species. Journal of Environmental Horticulture 22:12-16.

Wunderlin, R. P., and B. F. Hansen. 2008. Atlas of Florida Vascular Plants. URL http://www.florida.plantatlas.usf.edu/ [accessed on 6 January 2013]

WILDLAND WEEDS | SPRING 2014 | ONLINE SUPPLEMENT TO INCLUDE REFERENCES