Growth and development of two sea oats ( Uniola paniculata L.) genotypes with differing acclimatization capacities when transferred from in vitro to ex vitro greenhouse conditions were compared as a function of the duration of shoot multiplication and rooting stages. Anatomical and morphological development differed between genotypes in vitro. After 4, 8, and 12 weeks of Stage II culture, leaf length and shoot number were significantly greater for the easy-to-acclimatize genotype (EK 16-3) than the difficult-to-acclimatize genotype (EK 11-1). Shoot dry weights in both genotypes were greatest after 4 weeks culture. Browning and dying of tissue steadily increased with time. Shoot number per plantlet increased from Week 4 to 8 in both genotypes but decreased after 12 weeks. Once transferred to Stage III culture for 6 weeks, significant differences in root architecture and morphology were observed between the two genotypes. EK 16-3 plantlets developed short but numerous roots and “grass-like” leaves with fully expanded blades. Conversely, EK 11-1 plantlets developed few long roots and “lance-like” leaves, which were short, thick, and without expanded blades. Anatomical and morphological development during Stage III differed between culture duration and genotypes. Shoot and root dry weights of both genotypes increased during 3, 6, and 9 weeks of culture. Shoot dry weights of EK 16-3 plantlets were lower at 3 weeks but higher at 9 weeks than EK 11-1. Conversely, root dry weights were higher for EK 11-1 than for EK 16-3 plantlets throughout Stage III culture. Anatomical observations of EK 11-1 plantlets using light and electron microscopy correlated poor ex vitro acclimatization and poor survival with abnormal tissue organization, stomatal aperture blockage, and thylakoid membrane disruption.

Invasive species have disrupted thousands of acres of natural areas in Florida and appear to have a physiological competitive advantage over native species. The influence of light and temperature on germination was determined for the invasive Mexican petunia ( Ruellia tweediana Griseb.) and native wild petunia ( Ruellia caroliniensis Steud.). Seeds were collected and germinated in incubators with light or darkness at 15, 24, 33, and 30/20 °C. Light increased germination for each species, except at 15 °C ( R. caroliniensis ). For R. caroliniensis , highest germination (86% to 94%) occurred at 33 °C and 30/20 °C. Highest germination of R. tweediana (98% to 100%) occurred at 30/20 °C. Studies also were initiated to determine if R. tweediana has a competitive advantage over the native species when grown under wet and dry substrate conditions. Growth and development measurements after 8 weeks under controlled conditions revealed that R. tweediana grown in wet conditions had the greatest dry weight increase as compared to other treatments. Ruellia caroliniensis had higher specific leaf area when grown in wet or dry conditions, as compared to R. tweediana . Throughout the experiment, net CO ₂ assimilation of R. caroliniensis grown under dry or wet conditions was consistently lower than that of R. tweediana . Shoot nitrogen and phosphorus use efficiencies were generally greatest for R. tweediana plants grown in wet conditions. For shoot nutrient content, significant species × moisture interactions occurred for measured phosphorus (P) and calcium (Ca). When grown in wet conditions, R. tweediana had less shoot P and Ca as compared to dry conditions. For root nutrient content, species × moisture interactions were insignificant for each measured nutrient, with the exception of potassium (K). Potassium use efficiency of R. tweediana roots grown in wet conditions was higher than that of R. tweediana grown in dry conditions and R. caroliniensis grown in wet conditions.

The ornamental horticulture industry has long been significant in its vast economic contributions to the US agricultural sector, with Florida ranking second in nursery and greenhouse plant sales. A small proportion of introduced plants eventually escape cultivation and become invasive, leaving fragile ecosystems at risk. In response, a series of propagation and production research studies have been conducted over the years to 1) evaluate the female sterility and landscape performance of cultivars and/or hybrids of ornamental invasives, and 2) develop reliable propagation systems of novel or underused natives having ornamental and ecological value. Attractive, fruitless selections of popular species such as butterfly bush ( Buddleja sp.), heavenly bamboo ( Nandina domestica ), Mexican petunia ( Ruellia simplex ), lantana ( Lantana strigocamara ), trailing lantana ( Lantana montevidensis ), privet ( Ligustrum sp.), maiden silvergrass ( Miscanthus sp.), and fountain grass ( Pennisetum sp.) have been identified as suitable non-native alternatives to the invasive or potentially invasive resident species (wild type). Simultaneously, researchers have taken a closer look at native plant alternatives that may offer similar aesthetic traits as invasive plants, while bringing added biodiversity and function for more ecologically friendly landscapes and gardens. As such, successful multisite trialing and/or propagation systems have been developed for a number of species native to Florida, such as squareflower ( Paronychia erecta ), coastalplain honeycombhead ( Balduina angustifolia ), wireweeds ( Polygonella sp.), blue porterweed ( Stachytarpheta jamaicensis ), wild coffees ( Psychotria sp.), sweet acacia ( Vachellia farnesiana ), and wild lime ( Zanthoxylum fagara ). With pronounced marketing and consumer education, it is hopeful that together sterile cultivars and native species will ultimately replace wild-type forms of commercially available ornamental invasives. This paper summarizes the current status of ornamental invasives in Florida and the role of native species and sterile non-native cultivars.

A wild-type selection of heavenly bamboo ( Nandina domestica ) and eight cultivars were evaluated in northern and southern Florida for 144 weeks. Onset of flowering generally began by April and May in southern Florida and 4 to 8 weeks later in northern Florida. Fruit was first noted 4 to 8 weeks after most cultivars began flowering. Landscape performance and fruit production varied widely among taxa and location. ‘AKA’, ‘Firehouse’, ‘Firepower’, and ‘Firestorm’ heavenly bamboo did not flower or fruit in either location. Greater plant growth, survival, and fruiting were observed in northern Florida than in southern Florida. In both locations, the wild-type form of heavenly bamboo produced more fruit than ‘Alba’, ‘Gulf Stream’, ‘Monfar’, and ‘Moyer’s Red’. Seed viability was fairly consistent among fruiting cultivars, ranging from 69% to 89%. Nuclear DNA content and ploidy analysis indicated that all nine nandina cultivars were diploids, suggesting that tetraploidy is not the genetic cause of the non-fruiting trait in ‘AKA’, ‘Firehouse’, ‘Firepower’, and ‘Firestorm’. Results of this study offer insight into future non-invasive heavenly bamboo breeding efforts and emphasize the importance of cultivar and geographic distinctions when regarding the invasive status of a species.

Helianthus verticillatus Small, the whorled sunflower, is a perennial species only found at a few sites in the southeastern United States and was declared federally (USA) endangered in 2014. The species spreads locally via rhizomes and can produce copious seeds when sexually compatible genotypes are present. Vegetative propagation of the species via cuttings and the optimum conditions for seed germination have not been determined. To investigate asexual propagation via cuttings, stem sections were harvested in late May, June, and July in Knoxville, Tennessee (USA) and trimmed to a minimum of two nodes. The base of the cuttings was treated with either auxin or water, and grown in a Promix BX potting medium with intermittent mist and 50% shade for one month. Seeds were harvested from a population of multiple genotypes in Maryville, Tennessee and used to determine viability and the range of temperatures suitable for germination. A clonal population was developed and used for three years to assess sexual compatibility at three locations in Knoxville, Tennessee. Ninety-five percent of the cuttings from May rooted in two-to-three weeks and formed more than 20 adventitious roots per cutting with auxin and 18 with water treatments. The ability of cuttings to root decreased in June to about 20%, and none rooted in July with either water or auxin pretreatments. Pre-germination tetrazolium tests indicated that about 91% of seeds (achenes) were viable. Subsequent germination tests revealed high germination at varying temperatures (96 to 99% of seeds (achenes) germinated at 22/11, 27/15, and 29/19 °C), whereas germination was significantly inhibited by 33/24 °C. Fifty percent of the seeds germinated at 22/11 °C in 7.5 days, whereas only 2.0 to 2.5 days were required for 50% germination at 27/15, 29/19, and 33/24 °C. Seeds were not produced at any of the clonal planting locations during the three years. Vegetative propagation via rooted cuttings was successful in the mid-spring, seed germination was possible over a wide range of temperatures, and self-incompatibility was evident in this species. The results of this study will permit fast and efficient propagation of multiple and selected genotypes for conservation, commerce, and breeding of elite cultivars with disease resistance or other desirable attributes.