Full sun trial gardens were established at two sites in northern Florida. Six U.S. native and three non-native warm season grass species were evaluated in a split-plot design. Only eastern gamagrass (Tripsacum dactyloides), elliott's lovegrass (Eragrostis elliottii), gulf hairawn muhly (Muhlenbergia capillaris), little bluestem (Schizachyrium scoparium), and ‘Central Park' maiden grass (Miscanthus sinensis) showed a significant response to supplemental irrigation or fertilization. Supplemental irrigation did not influence foliage height for any of the grasses, whereas supplemental fertilization influenced foliage height only for chinese fountain grass (Pennisetum alopecuroides). The response differences between locations were attributed in part to soil types. This study observed minimal or no response of shoot growth to supplemental irrigation or fertilization for the grass species tested, thereby affirming the broad adaptability and minimal need for inputs for these ornamental landscape plants.
Mack Thetford, Gary W. Knox, and Edwin R. Duke
Rosanna Freyre, Adam Moseley, Sandra B. Wilson, and Gary W. Knox
Mexican petunia (Ruellia simplex Wright) is a non-native plant that was introduced to Florida sometime in the 1940s and since then has naturalized in most of the state and in other southern states. Since 2007, we have developed at the University of Florida/Institute for Food and Agricultural Science in Gainesville the first Ruellia L. breeding program aiming to develop fruitless plants with different flower colors and growth habits that will not be invasive by seed dispersal. A combination of polyploidization and hybridization methods was used. In 2011, a total of 15 plants were selected and grown in southeastern, north–central, and northwestern Florida (Fort Pierce, Citra, and Quincy) using a randomized block design with three blocks and three plants per plot at each site. Plants were evaluated monthly for landscape performance, flowering, and fruiting. Two hybrids (R10-102 and R10-108) had outstanding potential as new fruitless cultivars for the plant industry having improved landscape performance and flowering.
Jyotsna Sharma, Gary W. Knox, and Maria Lucia Ishida
Certain cultivars of magnolia are desirable in landscapes for their uncommon yellow flowers. While cultivars derived from Magnolia acuminata L. (cucumbertree magnolia) are difficult to propagate by stem cuttings, some with mixed parentage appear easier to propagate in this manner. We propagated six yellow-flowered cultivars vegetatively by applying 0, 8, 16, or 30 g·kg–1 (0, 8,000, 16,000, or 30,000 ppm) indole-3-butyric acid (IBA) in talc to bases of terminal stem cuttings collected 5, 7, 9, or 11 weeks after budbreak. Mean rooting percentage over all cultivars increased from 12% (in the absence of IBA) to 34% (after application of 30 g·kg–1 IBA). Rooting percentage and basal stem diameter of a cutting did not seem related. For each collection date, more cuttings of `Ivory Chalice' and `Yellow Lantern' developed roots than the other cultivars. More roots (mean = 5) developed on cuttings of `Yellow Lantern' collected 5 weeks after budbreak or when treated with 30 g·kg–1 IBA than the other cultivars. `Butterflies' largely remained unresponsive, whereas rooting of `Golden Sun,' `Hot Flash,' and `Maxine Merrill' collected 5 weeks after budbreak was 31%, 22%, and 28%, respectively. When data were analyzed separately for selected cultivars, 63% rooting was observed among cuttings of `Ivory Chalice' collected 7 weeks after budbreak. Rooting percentage was higher (22%) among cuttings of `Hot Flash' collected 5 or 7 weeks after budbreak in comparison to later collection dates, but harvest date did not influence rooting of `Yellow Lantern,' which ranged from 44% to 59%. Collection of stem cuttings early in the growing season (5 weeks after budbreak) was beneficial (31% rooting) for inducing rooting among cuttings of `Golden Sun.' We conclude that `Ivory Chalice' and `Yellow Lantern' are promising choices for growers interested in clonal propagation of yellow-flowered cultivars of magnolia. To maximize rooting among these cultivars, terminal cuttings should be collected within 5 to 11 weeks after budbreak and treated with 16 or 30 g·kg–1 IBA in talc. Early collection dates (5 to 7 weeks after budbreak) improved rooting among cuttings of other cultivars but these, particularly `Butterflies,' remain variably recalcitrant and merit further study.
Sandra B. Wilson, Gary W. Knox, Keona L. Nolan, and James Aldrich
Chinese privet (Ligustrum sinense) and glossy privet (L. lucidum) have been classified as Category I invasives in Florida. The closely related japanese privet (L. 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-hour 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.
Sandra B. Wilson, Gary W. Knox, Zhanao Deng, Keona L. Nolan, and James Aldrich
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.
David M. Czarnecki II, Sandra B. Wilson, Gary W. Knox, Rosanna Freyre, and Zhanao Deng
Heather Kalaman, Gary W. Knox, Sandra B. Wilson, and Wendy Wilber
As land-use patterns change over time, some pollinating insects continue to decline both in abundance and diversity. This is due, in part, to reductions in floral resources that provide sufficient nectar and pollen. Our overall goal is to help increase the use of plants that enhance pollinator health by providing research-based information that is easily accessible to the public. To assess the most successful mode of sharing this information, a survey was distributed to more than 4000 Master Gardener (MG) volunteers of Florida. The objectives of our survey were to gauge both knowledge and interest in common pollinators, common pollinator-friendly floral resources, and a favored means of accessing material about additional pollinator-friendly plants for landscape use. With a response rate of just over 18%, results showed that there is a clear interest among Florida MGs in learning more about pollinators and pollinator-friendly plants with face-to-face classes followed by a website as the preferred modes of accessing educational materials on this topic. Respondents on average were extremely interested in learning more about pollinator plants [mean of 4.41 out of 5.0 (sd = 0.89)], with greatest interest in butterflies/moths (Lepidoptera), followed by bees (Hymenoptera), birds (Aves), bats (Chiroptera), and beetles (Coleoptera). Overall, MG participants felt more confident (P < 0.0001) in their knowledge of pollinator-friendly plants (mean 3.24 out of 5.0) than pollinator insects (mean 3.01 out of 5.0). When tested, 88.5% were able to correctly identify black-eyed susan (Rudbeckia hirta), with 70.1% correctly identifying spotted beebalm (Monarda punctata). Variations were observed in tested knowledge of pollinating insects, with 90.2% correctly identifying a zebra longwing (Heliconius charithonia) and only 32.6% correctly identifying a striped-sweat bee (Agapostemon splendens). These results revealed that MGs perceived themselves to be fairly knowledgeable about both pollinator plants and pollinating insects, yet their tested knowledge ranged widely depending on the actual plant and pollinator type. This suggests an emphasis be given for future MG training focused on diverse plant and pollinator species, preferably in a face-to-face environment. Results also show that additional resources regarding pollinator-friendly plants, as well as identification material on pollinating insects, are both desired and valued by our Florida MG community.
Mohammed I. Fetouh, Abdul Kareem, Gary W. Knox, Sandra B. Wilson, and Zhanao Deng
A number of privet species (Ligustrum spp.) that are important to the nursery and landscape industry have escaped cultivation and become invasive or weedy in the United States and other countries. Induced tetraploids in these species may produce new selections or cultivars with reduced or eliminated invasive potential. Applying drops of semisolid agar containing 0.1% to 0.3% colchicine and 0.2% dimethyl sulfoxide (DMSO) to newly emerged seedlings of japanese privet (Ligustrum japonicum Thunb.) resulted in 15.6% to 22.6% tetraploid induction. The nuclear DNA content of tetraploids was 5.31 pg/2C, 101.9% higher than that of diploids. Compared with diploid plants, tetraploids were more compact, with an average of 31.0% shorter plant height and 33.1% smaller canopy width. Tetraploids had 29.2% thicker internodes, and their leaves were 39.5% larger and 33.8% thicker, resulting in 42.1% to 24.1% greater fresh or dry leaf weights (per leaf) in tetraploids compared with diploids. Without indole-3-butyric acid (IBA) treatment, cuttings from tetraploids showed 28% lower rooting than diploids. IBA treatments improved the rooting of tetraploid cuttings, resulting in 65% rooting success. These results indicate that tetraploids can be readily induced in japanese privet and induced tetraploids show significant changes in plant growth and size, shoot growth, leaf morphology, and rooting of cuttings. The modified tetraploid induction method and the induced tetraploids are expected to be useful for producing new selections or cultivars with reduced invasive potential in japanese and other privets.
Binoy Babu, Gary Knox, Mathews L. Paret, and Francisco M. Ochoa-Corona
Rose rosette emaravirus (RRV, genus Emaravirus), the causal agent of rose rosette disease, is the topmost pathogen of concern for the rose industry in the United States. The only strategy available for disease management is early identification and eradication of the infected plants. Highly reliable, specific, and sensitive detection assays are thus required to test and confirm the presence of RRV in suspected plant samples. RRV is only a recently characterized virus and hence limits the diagnostic tools available for its early detection. With a U.S. Department of Agriculture (USDA) Specialty Crop Research Initiative (SCRI) project sponsorship, several diagnostic tools including end-point reverse transcription-polymerase chain reaction (RT-PCR) and RT-qPCR assays targeting single and multiple genes targets were developed for routine diagnostics. This review introduces an overall view of the different diagnostic tools developed, which are reliable, highly sensitive, and can be easily implemented for detection and identification in laboratories providing diagnostic services and confirmation of RRV-infected samples.
Benjamin D. Anderson, Gary W. Knox, Ann R. Blount, Cheryl L. Mackowiak, and Edward F. Gilman
Rhizoma peanut has the potential for use as an ecologically friendly groundcover or turf alternative. Little is known about height and cover characteristics of this plant, which are important ornamental considerations. The objectives of this field study were to characterize maximum average canopy height, height variability, the time to reach full canopy cover, and the time at full canopy cover of seven released and nine experimental selections of rhizoma peanut grown in full sun or under 30% shade at two North Florida locations. Greater height and a less uniform canopy were observed for shaded plants. Establishment, as measured by full canopy cover, did not occur until the second year after planting. Shade treatment had little effect on the time to reach full canopy cover or the duration of full canopy cover, indicating that rhizoma peanut will perform equally in full sun or under 30% shade. Recommended selections for ornamental use based on these variables include ‘Brooksville 67’, ‘Brooksville 68’, EX3, and EX8.