ASSESSING AND CONTROLLING THE INVASIVENESS OF ORNAMENTAL SPECIES IN FLORIDA

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0216408
• Project Start Date: Oct 1, 2008
• Project End Date: Sep 30, 2013
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611

Performing Department
Indian River Research and Education Center, Ft Pierce

Non Technical Summary
Approximately 15% of the 10 million acres of public conservation lands in Florida have been disrupted by invasive nonindigenous plants, costing the state more than $29 million annually for control and management practices (Don Schmitz, personal communication, 2005). The majority of plants considered invasive today were originally introduced as ornamentals and there is often a lag time between when a species is determined to be invasive and when it is no longer produced commercially. An alarming 60% of plants on The Florida Nursery Growers and Landscape Association?s (FNGLA) voluntary ?do not sell? list (compiled in 2001) were still commercially available in 2004 from Florida nurseries (Caton, 2005). About 27% of FLEPPC Category I and II species are still commercially available in Florida, with some having more than 100 known cultivars that could potentially impact our natural areas. Some cultivars have the potential to cross with closely related native species. Controlled crossing can definitively tell us if they are a potential threat to our native flora. Research is critical to provide scientific evidence of the potential negative impacts invasives may have with regards to crossing with related native species, seedling trueness to type, invasive potential, and site specificity. We propose to evaluate Category I and II ornamental species that are currently available in the nursery trade. Field trials will be conducted in north and south FL and subsequent seeds will be subjected to viability and germination tests. Three of the most popular ornamental species (Mexican Petunia, Lantana, and Nandina) will be subjected to breeding selection for genetic sterilization. Potential for hybridization between native and invasive genera will be assessed. This information will be directly beneficial to our scientific community, nursery industry, and general gardening community.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
206	2120	1020	50%
206	2110	1020	50%

Knowledge Area
206 - Basic Plant Biology;

Subject Of Investigation
2110 - Ornamental trees and shrubs; 2120 - Herbaceous perennials and decorative greens;

Field Of Science
1020 - Physiology;

Keywords

invasive exotics

ornamentals

fleppc

nandina

mexican petunia

lantana

seed viability

sterilization

Goals / Objectives
The overall project objective is to characterize the potential invasiveness of ornamental species in Florida with a proactive plant management approach. Specific objectives are to: 1- Investigate the potential invasive impact (growth rate, flowering period, seed production, germination requirements) of highly cultivated FLEPPC Category I or II ornamentals (or other likely invasive candidates that have not been ranked), 2- Devise effective approaches for sterilizing invasive species that have been designated as high risk but are still commercially available, and 3- Through controlled crosses, determine 'true to typeness' of cultivars and the future genetic impact the selected species may have in natural areas.

Project Methods
Objective 1-Field plantings of nine uniform plants of each species (and respective cultivars) will be planted in south Florida (Fort Pierce) and north Florida (Quincy) and spaced 1.2 m (4 ft) on center in beds covered with polyethylene landscape fabric. Visual quality (plant color and form) will be independently assessed monthly by three individuals for each species at each location. At the termination of the study, plant height and two perpendicular widths will be recorded prior to dry weight destructive measurements of shoots. Observations of flower initiation and fruit set will be recorded monthly in north and south Florida. Seeds will be subjected to germination and viability tests. Germination conditions (substrate, temperature, photoperiod, duration) will vary by species. Data will be subjected to ANOVA and significant means separated accordingly. Outputs will be presented in oral and written format to the scientific and general community. Research results will significantly impact grower decisions for propagation, production and distribution of potentially invasive species. Objective 2- Procedures for tetraploid induction and triploid production for genetic sterilization will be conducted on lantana, nandina, and Mexican petunia. Generation of sterile triploids involves several steps, including tetraploid induction and identification, interploid (diploid and tetraploid) cross pollination, triploid recovery and identification, and triploid evaluation. To obtain a higher efficiency of solid tetraploids (rather than mixoploids), the in vitro induction method (Murashige and Nakano, 1966) will be used. This will include developing plant tissue culture stock, multiplication of shoots, rooting, and plant establishment in a greenhouse environment. Objective 3- R. caroliniensis and R. tweediana plants will be grown in two separate greenhouses to exclude potential insect-mediated pollination. Artificial hybridization will be conducted in both directions, i.e. R. caroliniensis (female) x R. tweediana (male) and R. tweediana (female) x R. caroliniensis (male). Both species are self-compatible; thus, flowers of seed parents need to be emasculated. At least 30 flowers will be pollinated per cross. After four to five weeks, mature capsules will be harvested and seeds will be collected and examined. The plumb seeds will be collected from each cross and subjected to germination tests following the procedure of Wilson and Mecca (2003). Five to 10 seedlings from each cross will be grown in the greenhouse until maturity. Pollen will be collected from F1 hybrids and the selfing progeny. Flowers of these plants will be allowed to pollinate openly (without hand pollination or bagging) in the greenhouse; seed production will be examined, and seeds (F2 generation) will be germinated to determine the fertility of F1 hybrids between the two species. Similar procedures will be used to determine cross compatibility between S. cayennensis (Category II) and S. jamaicensis (FL native).

Progress 10/01/08 to 09/30/13

Outputs
Target Audience: The target audience is the scientific horticultural community, nursery and landscape association, and environmental government agencies Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Project directors havepresented scientific findingsin over 25 professional associations worldwide within the last 5 years. Research has been translated to the community by providing regional talks to environmental and nursery organizations.At least 6undergraduateor graduate students have been trained as part of the project. Invited lectures have been given to statewide courses in environmental horticulture, reaching hundreds of students each semester. How have the results been disseminated to communities of interest? Research has been broadly disseminated to native plant societies, extension tranining workshops, exotic pest plant councils, master gardeners, garden clubs, and landcape and nursery associations. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? The substantial economic and ecological costs of invasive plant management and removal warrant aggressive eradication and prevention programs. Ornamental horticulture has been recognized as the fastest growing segment of U.S. Agriculture, as well as the main source of plant invasions worldwide. Florida ranks second among U.S. states in the degree of ecosystem devastation as a result of exotic invasive species. Cultivated or improved forms of a number of the ornamental species listed as invasive by Florida’s Exotic Pest Plant Council have been selected for their attractive flower color, plant form, foliage, drought tolerance, or cold hardiness. As the cultivars are generally propagated vegetatively, relatively little is known about their pollination biology, seed production, seed viability and growth rate under varying conditions. To identify safe alternatives to ornamental invasives, researchers at the University of Florida have evaluated numerous cultivars of Mexican petunia (Ruellia tweediana), privet (Ligustrum spp.), fountain grass (Pennisetum spp.), porterweed (Stachytarpheta spp.), heavenly bamboo (Nandina domestica), and lantana (Lantana camara). These species are not only problematic in Florida, but highly invasive in other parts of the world. Research efforts have identified and evaluated sterile non-invasive forms of these species, with statewide trailing and evaluation.

Publications

• Type: Journal Articles Status: Published Year Published: 2014 Citation: Wilson, S.B., G.W. Knox, Z. Deng, K.L. Nolan, and J. Aldrich. 2014. Landscape performance and fruiting of nice heavenly bamboo selections grown in northern and southern Florida. HortScience. 49:706-713.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Freyre, R. and S.B. Wilson. 2014. Ruellia simplex R10-105-Q54 (Mayan Pink). HortScience. 49:499-502.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Wilson, S.B., G.W. Knox, K.L. Nolan, and J. Aldrich. 2014. Landscape performance and fruiting of 12 privet selections grown in northern and southern Florida. HortTechnology. 24:148-155.
• Type: Journal Articles Status: Published Year Published: 2012 Citation: 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.
• Type: Journal Articles Status: Published Year Published: 2012 Citation: Freyre, R., A. Moseley, S.B. Wilson, and G.W. Knox. 2012. Breeding and evaluating for landscape performance and fruitlessness in Mexican Petunia (Ruellia, Acanthaceae). HortScience. 47:1245-1251.
• Type: Journal Articles Status: Published Year Published: 2012 Citation: Czarnecki,D.M., S.B. Wilson, G.W. Knox, R. Freyre, and Z. Deng. 2012. UF-T3 and UF-T4: Two sterile Lantana camara cultivars. HortScience. 47:132-137.
• Type: Conference Papers and Presentations Status: Published Year Published: 2010 Citation: Wilson, S.B., G.W. Knox, Z. Deng, and R. Freyre. 2010. Characterizing the invasive potential of ornamental plants. Proceedings of the XXVIII International Horticulture Congress on Science and Horticulture for People. Acta Horticulturae. 937:1183-1192.
• Type: Journal Articles Status: Published Year Published: 2009 Citation: 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.
• Type: Journal Articles Status: Published Year Published: 2009 Citation: Wilson, S.B. and G.W. Knox. 2009. Landscape performance of green fountain grass alternatives grown in northern and southern Florida. HortTechnology. 19:471-476.

Progress 10/01/12 to 09/30/13

Outputs
Target Audience: Scientific community, Florida Nursery and Growers Association, FLEPPC, horticulture society Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Annual presentation at ASHS meetings How have the results been disseminated to communities of interest? Website, trade articles. news releases, oral presentations to local garden clubs What do you plan to do during the next reporting period to accomplish the goals? Continue to publish research

Impacts
What was accomplished under these goals? Chinese privet (Ligustrum sinense) and glossy privet (Ligustrum lucidum) have been classified as Category I invasives in Florida. The closely related japanese privet (Ligustrum japonicum) has escaped cultivation but is not considered a problem species in Florida. Plant growth, visual quality, flowering, and fruiting were assessed for the resident species (wild type form) and selected cultivars of chinese privet, glossy privet and japanese privet planted in northern and southern Florida for 132 weeks. Visual quality varied by site, month and cultivar. With the exception of 'Swift Creek' chinese privet (which did not survive in southern Florida), all cultivars survived the study. All plants fruited in northern Florida. In southern Florida, fruiting was less abundant and not observed for 'Jack Frost' japanese privet, 'Rotundifolium' japanese privet, 'Swift Creek' chinese privet, 'Suwannee River' hybrid privet and glossy privet within 132 weeks. In northern and southern Florida, the growth index rate was lower for 'Lake Tresca' japanese privet, 'Rotundifolium' japanese privet and 'Suwannee River' hybrid privet than other cultivars. There was a significant interaction between temperature and species for seed germination. Germination in incubators set with a 12 hr photoperiod ranged from 51 to 78.5% for chinese privet, japanese privet and glossy privet among temperatures, with the exception of glossy privet at 35/25 °C, where only 2.0% of seeds germinated. Germination in complete darkness ranged from 39.5 to 80.5% for chinese privet and glossy privet among temperatures, with the exception of glossy privet at 35/25 °C, where only 0.5% of seeds germinated.

Publications

• Type: Journal Articles Status: Published Year Published: 2013 Citation: Wilson, S.B., G.W. Knox, K.L. Nolan, and J. Aldrich. 2013. Landscape performance and fruiting of 12 privet selections grown in northern and southern Florida. HortTechnology. 24:1-6. Krueger, K., S.B. Wilson, K. Moore, G.W. Knox, and Z. Deng. 2013. National ornamental grass trial-University of Florida, Ft. Pierce 1st year results. Proc. South. Nurs. Assoc. 58:184-186. 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. Proc. VIIth International Symposium on New Floricultural Crops. Eds.: G. Facciuto and M.I. Sanchez. Acta Hort. 1000:423-428.

Progress 10/01/11 to 09/30/12

Outputs
OUTPUTS: Over the last decade, our research efforts have focused on assessing the invasive traits of popular ornamentals, closely related genera, and/or cultivated forms to identify safe alternatives. These include butterfly bush (Buddleja spp.), lantana (Lantana camara), privet (Ligustrum spp.), Mexican petunia (Ruellia tweediana), porterweed (Stachytarpheta cayennensis), heavenly bamboo (Nandina domestica), fountain grass (Pennisetum spp.), and Japanese silvergrass (Miscanthus sinensis). Chinese privet (Ligustrum sinense) and glossy privet (Ligustrum lucidum) have widely naturalized throughout the southeast United States, dominating the understory of mesic forests and displacing native plant communities. In Florida, chinese privet and glossy privet have escaped cultivation and are listed by the Florida Exotic Pest Plant Council as Category I invasives and are not recommended for planting by the University of Florida IFAS status assessment protocol. A third privet, japanese privet (Ligustrum japonicum) has escaped cultivation but is not listed as invasive. All three species have ornamental value, with numerous cultivars commercially available. The University of Florida Ornamental Plant Breeding Program in Balm has developed sterile or almost sterile hybrids from existing cultivars (Z. Deng, personal communication). A wide range of ploidy levels (2x to 6x) exist in lantana cultivars. Pollen stainability varied from less than 1% to nearly 80% between cultivars, with a greater difference (>1000-fold) observed among cultivars in seed set. On average, diploids had the highest fertility, followed by tetraploids, pentaploids, and hexaploids. Tetraploids and diploids were hand-pollinated to produce several hundred lantana triploids that were subsequently tested for pollen viability and seed production in the greenhouse as well as in the field to determine their male and female sterility. Ploidy level and molecular marker analyses confirmed the existence of multiple reproduction pathways in lantana, including unreduced female gamete formation and apomixis, traits that should be selected against (Czarnecki et al., 2010). Highly sterile triploids were selected and further evaluated for their growth habit, plant form, foliage development, flower color, and flower size. Results from field trials consisting of ten new hybrid lines at four locations across Florida (north, central, south, and southwest) have shown that the male and female sterility in these triploids is generally stable and consistent. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
In summary, the substantial economic (Pimentel et al., 2005) and ecological (Simberloff, 1997) costs of invasive species management and removal warrant aggressive early detection and prevention programs. This research illustrates the importance of evaluating cultivars for invasiveness in more than one region. Several cultivars (already existing in the industry) of invasive plants have been approved for recommendation by the University of Florida Infraspecific Taxon Protocol. These include Nandina domestica 'Firepower', Nandina domestica 'Harbour Dwarf', and Ruellia tweediana 'Purple Showers'. Extensive breeding efforts to produce novel and safe cultivars are currently underway with statewide landscape trialing. Availability of non-invasive cultivars will provide the horticulture industry with a ready substitute to invasive species for continued use of these popular plants.

Publications

• Freyre, R., A. Moseley, Knox, G.W., and S.B. Wilson. 2012. Fruitless Ruellia simplex R10-102 'Mayan Purple' and R10-108 'Mayan White'. HortScience 47(12):1808-1814.
• Czarnecki,D.M., S.B. Wilson, G.W. Knox, R. Freyre, and Z. Deng. 2012. UF-T3 and UF-T4: Two sterile Lantana camara cultivars. HortScience. 47:132-137.
• Freyre, R., A. Moseley, S.B. Wilson, and G.W. Knox. 2012. Breeding and evaluating for landscape performance and fruitlessness in Mexican Petunia (Ruellia, Acanthaceae). HortScience. 47:1245-1251.
• Wilson, S.B., G.W. Knox, R. Freyre, and Z. Deng. 2012. Characterizing the invasive potential of ornamental plants. Proceedings of the XXVIII International Horticulture Congress on Science and Horticulture for People. Acta Hort. 937:1183-1192.
• Deng, Z., D.M. Czarnecki, S.B. Wilson, G.W. Knox, and R. Freyre. 2012. UF-T3 and UF-T4: Two sterile Lantana camara varieties. EDIS publication #ENH1202.
• Freyre, R., A. Moseley, C. Reinhardt-Adams, G. Knox, and S.B. Wilson. 2012. Limiting invasive Ruellia populations via breeding sterile cultivars and developing efficient control in natural areas. HortScience 47:S197.

Progress 10/01/10 to 09/30/11

Outputs
OUTPUTS: Over the last decade, our research efforts have focused on assessing the invasive traits of popular ornamentals, closely related genera, and/or cultivated forms to identify safe alternatives. These include butterfly bush (Buddleja spp.), lantana (Lantana camara), privet (Ligustrum spp.), Mexican petunia (Ruellia tweediana), porterweed (Stachytarpheta cayennensis), heavenly bamboo (Nandina domestica), fountain grass (Pennisetum spp.), and Japanese silvergrass (Miscanthus sinensis). Chinese privet (Ligustrum sinense) and glossy privet (Ligustrum lucidum) have widely naturalized throughout the southeast United States, dominating the understory of mesic forests and displacing native plant communities. In Florida, chinese privet and glossy privet have escaped cultivation and are listed by the Florida Exotic Pest Plant Council as Category I invasives and are not recommended for planting by the University of Florida IFAS status assessment protocol. A third privet, japanese privet (Ligustrum japonicum) has escaped cultivation but is not listed as invasive. All three species have ornamental value, with numerous cultivars commercially available. The University of Florida Ornamental Plant Breeding Program in Balm has developed sterile or almost sterile hybrids from existing cultivars (Z. Deng, personal communication). A wide range of ploidy levels (2x to 6x) exist in lantana cultivars. Pollen stainability varied from less than 1% to nearly 80% between cultivars, with a greater difference (>1000-fold) observed among cultivars in seed set. On average, diploids had the highest fertility, followed by tetraploids, pentaploids, and hexaploids. Tetraploids and diploids were hand-pollinated to produce several hundred lantana triploids that were subsequently tested for pollen viability and seed production in the greenhouse as well as in the field to determine their male and female sterility. Ploidy level and molecular marker analyses confirmed the existence of multiple reproduction pathways in lantana, including unreduced female gamete formation and apomixis, traits that should be selected against (Czarnecki et al., 2010). Highly sterile triploids were selected and further evaluated for their growth habit, plant form, foliage development, flower color, and flower size. Results from field trials consisting of ten new hybrid lines at four locations across Florida (north, central, south, and southwest) have shown that the male and female sterility in these triploids is generally stable and consistent. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
In summary, the substantial economic (Pimentel et al., 2005) and ecological (Simberloff, 1997) costs of invasive species management and removal warrant aggressive early detection and prevention programs. This research illustrates the importance of evaluating cultivars for invasiveness in more than one region. Several cultivars (already existing in the industry) of invasive plants have been approved for recommendation by the University of Florida Infraspecific Taxon Protocol. These include Nandina domestica 'Firepower', Nandina domestica 'Harbour Dwarf', and Ruellia tweediana 'Purple Showers'. Extensive breeding efforts to produce novel and safe cultivars are currently underway with statewide landscape trialing. Availability of non-invasive cultivars will provide the horticulture industry with a ready substitute to invasive species for continued use of these popular plants.

Publications

• Deng. Z., S. Smith, G.W. Knox, and S.B. Wilson. 2011. Induction and characterization of tetraploids in Nandina (Nandina domestica). HortScience. 46(9):S169.
• Knox, G.W., S.B. Wilson, Z. Deng, and R. Freyre. 2011. Alternatives to invasive plants commonly found in Florida landscapes. Florida Native Plant Society and FLEPPC Combined meetings.
• Deng, Z., S.B. Wilson, G.W. Knox, and R. Freyre. 2011. Identifying and developing non-invasive varieties in landscape plants: Progress and prospects. Proc. FSHS. Abstracts of the 2011 Meeting of the Florida State Horticultural Society (http://www.fshs.org/Meetings/2011/FSHS-2011-Abstracts.pdf).
• Wilson, S.B. and G.W. Knox. 2011. Landscape performance and invasive potential of 12 Ligustrum sinense, Ligustrum lucidum and Ligustrum japonicum cultivars grown in north and south Florida. Proc. South. Nurs. Assoc. 56:361-367
• Freyre, R., A. Moseley, C. Reinhardt-Adams, G.W. Knox, S.B. Wilson. 2011. Breeding Ruellia spp. and other ornamental plants at the University of Florida. ActaHort. Submitted.

Progress 10/01/09 to 09/30/10

Outputs
OUTPUTS: Over the last decade, our research efforts have focused on assessing the invasive traits of popular ornamentals, closely related genera, and/or cultivated forms to identify safe alternatives. These include butterfly bush (Buddleja spp.), lantana (Lantana camara), privet (Ligustrum spp.), Mexican petunia (Ruellia tweediana), porterweed (Stachytarpheta cayennensis), heavenly bamboo (Nandina domestica), fountain grass (Pennisetum spp.), and Japanese silvergrass (Miscanthus sinensis). Chinese privet (Ligustrum sinense) and glossy privet (Ligustrum lucidum) have widely naturalized throughout the southeast United States, dominating the understory of mesic forests and displacing native plant communities. In Florida, chinese privet and glossy privet have escaped cultivation and are listed by the Florida Exotic Pest Plant Council as Category I invasives and are not recommended for planting by the University of Florida IFAS status assessment protocol. A third privet, japanese privet (Ligustrum japonicum) has escaped cultivation but is not listed as invasive. All three species have ornamental value, with numerous cultivars commercially available. Clonally propagated ligustrum cultivars of each species were obtained in finished 1 gal pots. Field plantings of nine uniform plants of each cultivar were installed under full sun conditions in south FL and north FL. Plants were evaluated monthly for flowering and fruiting, and tri-monthly for visual quality. Visual quality was based on a scale from 1 to 5 where 1=poor, and 5=excellent. Visual quality and flowering varied by cultivar and site. Regardless of cultivar, after 72 weeks (Nov. 2009), north FL plants received higher visual quality ratings than south FL plants. However, 'Howard' japanese privet, 'Jack Frost' japanese privet, and 'Variegatum' chinese privet had very good to excellent landscape performance at both sites. After 72 weeks, north Fla. plants were 1.2 to 2.8 times larger and produced more fruit than south Fla. plants. Seed viability and germination experiments were conducted from larger, independent populations of chinese privet, glossy privet and japanese privet. Pre-germination viability was 77% (chinese privet), 96% (glossy privet), and 37% (japanese privet) correlating to 68%, 90%, and 21% germination in the greenhouse, respectively. Germination varied by temperature and light. Under a 12 hr photoperiod, chinese privet had the greatest germination (79%) at 20/10 C, followed by glossy privet (76%) at 20/10 C, followed by japanese privet (71%) at 25/10 C. Field trials will continue until cultivars produce enough fruit for evaluation and to determine stability of variegation. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
In summary, the substantial economic (Pimentel et al., 2005) and ecological (Simberloff, 1997) costs of invasive species management and removal warrant aggressive early detection and prevention programs. This research illustrates the importance of evaluating cultivars for invasiveness in more than one region. Several cultivars (already existing in the industry) of invasive plants have been approved for recommendation by the University of Florida Infraspecific Taxon Protocol. These include Nandina domestica 'Firepower', Nandina domestica 'Harbour Dwarf', and Ruellia tweediana 'Purple Showers'. Extensive breeding efforts to produce novel and safe cultivars are currently underway with statewide landscape trialing. Availability of non-invasive cultivars will provide the horticulture industry with a ready substitute to invasive species for continued use of these popular plants.

Publications

• Wilson, S.B., G.W. Knox, Z. Deng, and R. Freyre. 2010. Characterizing the invasive potential of ornamental plants. Acta Hort. In press.
• Wilson, S.B., G.W. Knox, Z. Deng and R. Freyre. 2010. Non-invasive alternatives to Stachytarpheta cayennensis (Nettleleaf porterweed) grown in north and south FL. Proc. South. Nurs. Assoc.55:1-5.
• Wilson, S.B. and G.W. Knox. 2010. Assessing the invasive potential of 12 Ligustrum sinense, Ligustrum lucidum, and Ligustrum japonicum cultivars grown in northern and southern Florida. HortScience. In press.
• Knox, G.W. and S.B. Wilson. 2010. Risk assessment and research response of Florida-invasive ornamentals and their cultivars. HortScience. In press.

Progress 10/01/08 to 09/30/09

Outputs
OUTPUTS: Nettleleaf porterweed (Stachytarpheta cayennensis) is a potentially invasive ornamental plant in Florida. Plant growth, visual quality, flowering, and seed viability were assessed for nettleleaf porterweed and eight closely related alternatives planted in northern and southern Florida. In northern Florida, 'Mario Pollsa' porterweed (Stachytarpheta spp.), 'Violacea' porterweed (Stachytarpheta mutabilis), 'Naples Lilac' porterweed (Stachytarpheta spp.), 'Red Compact' porterweed (Stachytarpheta speciosa), and nettleleaf porterweed (Stachytarpheta cayennensis) achieved high flower ratings between 4 (average to good flowering) and 5 (abundant flowering, peak bloom) during four or more months. Also, jamaican porterweed (Stachytarpheta jamaicensis), 'Violacea' porterweed, 'Red Compact' porterweed, and nettleleaf porterweed achieved visual quality ratings between 4 and 5 (good to excellent quality) throughout most of the study. In southern Florida, the same cultivars received high flower ratings, but generally for shorter periods of time. Also, 'Violacea' porterweed and 'Red Compact' porterweed consistently received visual quality ratings that were above 4 (good quality, very desirable). During the course of the 28 week study, nettleleaf porterweed produced the greatest number of spiked inflorescences with 39% to 80% seed viability. At both locations, 'Violacea' porterweed did not produce any viable seed; and seed viability was less than 10% for 'Mario Pollsa' porterweed, coral porterweed (Stachytarpheta mutabilis), and 'Naples Lilac' porterweed. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
In the United States, an estimated 5000 plant species have escaped cultivation and are now established in natural ecosystems. The cost associated with invasive plant damage and control is estimated at nearly 35 billion dollars a year (Pimentel et al., 2005). Despite widespread prevention and eradication efforts, plant invasions continue to rise and are increasing at a rate of 10% annually (Pimentel et al., 2005). In Florida, at least 47% of plants that are negatively affecting the environment were introduced for ornamental purposes (Gordon and Thomas, 1997). More than 2/3rds of the Category I and II invasives listed by the Florida Exotic Pest Plant Council (FLEPPC, 2009) were introduced for ornamental use (Gordon and Thomas, 1997). Of these, we estimate that 27% are still in commercial production. The probability of plants becoming naturalized increases significantly with the number of years the plants were marketed. In fact, the naturalization rate of plants sold for 30 years or more is 70% (Pemberton and Liu, 2009). We have compiled a list of 9 species that are (1) category I invasive in Florida, (2) highly ornamental and largely in production, thereby having significant propagule pressure and (3) have closely related native genera of which they are associated with or capable of displacing. By exploring their interactions in varying conditions, we can ascertain the magnitude of the competitive advantage invasives have over co-existing natives to better project future invasive expansion, encroachment and management needs.

Publications

• 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. and G.W. Knox. 2009. Landscape performance of green fountain grass alternatives grown in northern and southern Florida. HortTechnology. 19:471-476.
• Knox, G.W. and S.B. Wilson. 2009. 'Firepower' Nandina (Nandina domestica): A Noninvasive Nandina for Florida. EDIS publication, University of Florida, IFAS. ENH1116/EP381.