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Excessive irrigation and leaching are of increasing concern in container plant production. It can also necessitate multiple fertilizer applications, which is costly for growers. Our objective was to determine whether fertilizer and irrigation water can be applied more efficiently to reduce leachate volume and nutrient content without negatively impacting aboveground growth of Gardenia jasminoides ‘MAGDA I’. Plants were fertilized with one of three rates of a controlled-release fertilizer (subplots) (Florikan 18–6–8, 9–10 month release; 18.0N–2.6P–6.6K) [100 (40 g/plant), 50 (20 g/plant), and 25% of bag rate (10 g/plant)] and grown in 5.4-L containers outside for 137 days. Soil moisture sensor-controlled, automated irrigation was used to provide plants with one of four irrigation volumes (whole plots) (66, 100, 132, or 165 mL) at each irrigation event. All plants were irrigated when the control treatment (66 mL irrigation volume, 100% fertilizer treatment) reached a volumetric water content (VWC) of 0.35 m3·m−3. Plants in the different irrigation treatments were irrigated for 2, 3, 4, or 5 minutes, thus applying 66, 100, 132, or 165 mL/plant in the different irrigation treatments. Fertilizer rate had a greater effect on aboveground growth than irrigation volume with the 25% fertilizer rate resulting in significantly lower shoot dry weight (18.7 g/plant) than the 50% and 100% rates (25.3 and 27.3 g/plant respectively). Growth index was also lowest in the 25% fertilizer rate. Leachate volume varied greatly during the growing season due to rainfall and irrigation volume effects on leachate were most evident during the third, eighth, and ninth biweekly leachate collections, during which there was minimal or no rainfall. For these collections the control treatment of 66 mL resulted in minimal leachate (less than 130 mL over the 2-week leachate collection period), whereas leachate volume increased with increasing irrigation volumes. Pore water electrical conductivity (EC), leachate EC, NO3-N content, and PO4-P content were all highest with the 100% fertilizer rate, with the 66 mL irrigation treatment having the highest leachate EC for all fertilizer treatments. Cumulative leachate volumes for the 66 and 100 mL irrigation treatments were unaffected by fertilizer rate, whereas the 132 and 165 mL had greater leaching at the 25% fertilizer rate. Lower irrigation volumes resulted in reduced water and nutrient leaching and higher leachate EC. The higher leachate EC was the result of higher concentration of nutrients in less volume of leachate. The results of this study suggest that a combination of reduced fertilizer rates (up to 50%) and more efficient irrigation can be used to produce salable plants with reduced leaching and thus less environmental impact.

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Sustainable use of water resources is of increasing importance in container plant production as a result of decreasing water availability and an increasing number of laws and regulations regarding nursery runoff. Soil moisture sensor-controlled, automated irrigation can be used to irrigate when substrate volumetric water content (θ) drops below a threshold, improving irrigation efficiency by applying water only as needed. We compared growth of two Gardenia jasminoides cultivars, slow-growing and challenging ‘Radicans’ and easier, fast-growing ‘August Beauty’, at various θ thresholds. Our objective was to determine how irrigation can be applied more efficiently without negatively affecting plant quality, allowing for cultivar-specific guidelines. Soil moisture sensor-controlled, automated irrigation was used to maintain θ thresholds of 0.20, 0.30, 0.40, or 0.50 m3·m−3. Growth of both cultivars was related to θ threshold, and patterns of growth were similar in both Watkinsville and Tifton, GA. High mortality was observed at the 0.20-m3·m−3 threshold with poor root establishment resulting from the low irrigation volume. Height, width, shoot dry weight, root dry weight, and leaf size were greater for the 0.40 and 0.50 m3·m−3 than the 0.20 and 0.30-m3·m−3 θ thresholds. Irrigation volume increased with increasing θ thresholds for both cultivars. For ‘August Beauty’, cumulative irrigation volume ranged from 0.96 to 63.21 L/plant in Tifton and 1.89 to 87.9 L/plant in Watkinsville. For ‘Radicans’, cumulative irrigation volume ranged from 1.32 to 126 L/plant in Tifton and from 1.38 to 261 L/plant in Watkinsville. There was a large irrigation volume difference between the 0.40 and 0.50-m3·m−3 θ thresholds with little additional growth, suggesting that the additional irrigation applied led to overirrigation and leaching. Bud and flower number of ‘Radicans’ were greatest for the 0.40-m3·m−3 θ threshold, indicating that overirrigation can reduce flowering. The results of this study show that growth of the different G. jasminoides cultivars responded similarly to θ threshold at both locations. Similarities in growth and differences in irrigation volume at the 0.40 and 0.50-m3·m−3 θ thresholds show that more efficient irrigation can be used without negatively impacting growth.

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Salvia is the largest genus in the Lamiaceae with more than 1000 species. The species S. coccinea used in this study has naturalized in the southeastern United States and is an important plant for pollinators. This project aimed to improve phenotypic characteristics of S. coccinea for use in the landscape by selecting for increased petal size and unique petal color. Two elite accessions were selected for hybridization using the pedigree method. One selection displayed compact habit with bicolored coral and white flowers, while the other was slightly larger with solid red flowers. Selections were made based on improved flower color and larger petal size. The breeding program achieved a 25% increase in petal width and a more vivid petal color for the coral bicolored selections. Additionally, a 60% increase in petal width was achieved for red flowers. These novel selections are attractive plants for the landscape, displaying improved ornamental value and supporting local pollinator populations.

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Controlling the elongation of ornamental plants is commonly needed for shipping and aesthetic purposes. Drought stress can be used to limit elongation, and is an environmentally friendly alternative to plant growth regulators (PGRs). However, growers can be reluctant to expose plants to drought stress because they do not want to negatively affect overall plant quality and marketability. Knowing how and when stem elongation is affected by water availability will help to increase our understanding of how elongation can be controlled without reducing plant quality. Rooted Hibiscus acetosella Welw. ex Hiern. cuttings were grown in a growth chamber set to a 12-hour photoperiod at 25 °C. Two plants of similar size were used for each replication of the study to compare growth under well-watered and drought-stressed conditions. Time lapse photography was used to determine the diurnal patterns of elongation over the course of the replications. Evapotranspiration was measured using load cells. Well-watered and drought-stressed plants had similar diurnal patterns of elongation and evapotranspiration, demonstrating that both follow circadian rhythms and are not just responding to environmental conditions. Stem elongation was greatest at night and coincided with evapotranspiration decreases, with greatest elongation shortly after the onset of darkness. Elongation was minimal between 800 and 1000 hr when evapotranspiration increases. During the drought-stress portion of the replications, elongation of drought-stressed plants was 44% less than well-watered plants. Final plant height and shoot dry weight for the drought-stressed plants were 21% and 30% less than well-watered plants, respectively. Total leaf area, number of leaves, and number of new visible internodes were greater for well-watered plants than drought-stressed plants. Average length of visible internodes and leaf size were similar for drought-stressed and well-watered plants. If growers want to use drought stress for elongation control, they should ensure that plants are drought stressed before the onset of and during the dark period, when most elongation occurs.

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Salvia coccinea is a valuable flowering annual that attracts hummingbirds and bees to the garden, but few cultivars are commercially available. There is a limited range of petal colors and no leaf variegation. This research aimed to improve the ornamental value of S. coccinea by inducing mutations with ethyl methanesulfonate (EMS). The standard, red-flowered species was selected for treatment by exposing seeds to 0%, 0.4%, 0.8%, or 1.2% EMS for 8, 12, or 24 hours. The optimal treatment rate was determined to be 1.2% EMS for 8 hours, which generated desirable mutations near the median lethal dose (LD50). The M1 population had a 53% germination rate and was completely morphologically uniform. By the M2, mutations included differences in leaf shape and flower size in addition to albina, chlorina, virescens, and chimeral chlorophyll changes. A 1% mutation rate was achieved in this breeding program with seven unstable mutations and six stable mutations. The normalized difference vegetation index (NDVI) values were measured to determine differences in chlorophyll content between lethal albina mutations, chartreuse chlorina and virescens mutations, and typical leaf color. Future work will investigate the stability and heritability of chlorophyll variegation by hybridizing these selections with coral-flowered accessions of S. coccinea.

Open Access

Hibiscus acetosella Welw. ex Hiern. ‘Panama Red’ PP20,121 (Malvaceae) has generated public and grower interest due to its attractive red foliage and vigorous growth, however, a horticultural goal is to develop more compact forms. Even though organs of induced polyploids are often larger than the wild type, whole plants are often shorter in stature. Three studies were conducted to induce polyploidy and to evaluate the growth and reproductive potential of the resulting polyploids. In study 1, seeds were soaked for 24 hours in aqueous solutions of 0%, 0.2%, 0.4%, or 0.5% colchicine (w/v) plus 0.5% dimethyl sulfoxide. In studies 2 and 3, apical meristems of seedlings at the cotyledon stage were treated for 1 or 3 days with 0, 50, 100, or 150 μm oryzalin solidified with 0.8% agar. Visual observations and measurement of guard cells were used to identify plants that potentially had their chromosome number doubled. Flow cytometry of nuclei stained with DAPI was used for confirmation of polyploidy. No induced polyploidy was observed following seed treatment with colchicine at the rates and duration used in this study. One-time application of 50 μm oryzalin resulted in a single mixoploid (4x + 8x) in which the ploidy of the L-I, L-II, and L-III histogenic layers were identified as a 4–4-4 + 8, respectively. Three-day applications with 100 and 150 μm oryzalin resulted in an octoploid (8x) and a mixoploid (4x + 8x), respectively. The mixoploid from the 3-day treatment stabilized at the 8x level before flowering, but was identified as a 4 + 8-x-4 cytochimera. Plant height was reduced, leaves were smaller, internodes were shorter, and canopy volume was reduced in the octoploid (8x) form compared with the tetraploid (4x) form. Furthermore, in contrast to the tetraploid, the octoploid produced no self-pollinated seed and performed poorly as a staminate and pistillate parent in controlled crosses. This represents the first time oryzalin has been reported to induce polyploidy in Hibiscus L. section Furcaria DC. H. acetosella is an allotetraploid species with the genome composition AABB. The resulting autoallooctoploid (AAAABBBB) form of ‘Panama Red’ exhibits a more compact habit and reduced production of seed.

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In response to a mail survey of the landscape maintenance and lawn care (LM-LC) industry in metropolitan Atlanta, we learned that 76% of respondents fertilized lawns and turf and 68% fertilized ornamental beds. Less than one-fourth of those who provided fertilization services offered an organic fertility option; for those who reported an organic option, an average of 25% of their residential customers used such a service. Complete fertilizers (N-P2O5-K2O), ammonium nitrate, urea, and N solutions were the products applied by most respondents. Average amounts of N per application were ≈1.5 lb/1000 ft2 on lawns and 1.1 lb/1000 ft2 on ornamentals. Of firms that provide fertilization services, 88% use a predetermined application schedule, whereas 88% use visual observation and 69% use soil testing to guide fertilizer management. Only 5% reported using tissue analysis as a fertilizer management strategy. Nitrogen fertilizers were applied most frequently in the spring, with nearly equal amounts applied in summer and fall. Phosphorus was applied most commonly in the fall or spring. Relatively few firms reported applying significant amounts of either N or P in winter. Most respondents indicated that they received adequate information about fertilizers, but few received information about organic fertilization. Commercial sales representatives and trade magazines were cited most often as sources of information; university specialists were the least-cited formal source of information concerning fertilization. We have suggested some research and educational issues to be addressed based on these results.

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Illiciums, or star-anises, have increased in popularity in the nursery and landscape industries. However, confusion exists as to which taxa are tolerant of high light intensities during production and subsequent establishment in the landscape. We investigated the effect of two light intensity treatments, 45% and 100% full sunlight, on gas-exchange parameters of five Illicium taxa: Illicium anisatum L., I. floridanum Ellis. `Pebblebrook', I. henryi Diels., I. lanceolatum A.C. Sm., and I. parviflorum Michx. Ex. Vent. `Forest Green'. Light-response curves were determined for individual leaves, and mean response parameters calculated. Chlorophyll and total carotenoids were analyzed after extraction in acetone, with total chlorophyll also estimated with a SPAD chlorophyll meter. In general, highest rates of CO2 assimilation (Amax) and lowest rates of dark respiration (Rd) were found in the 45% light treatment for all taxa. Both Illicium anisatum and I. floridanum `Pebblebrook' had substantial reductions in Amax in 100% light, 94% and 81% respectively, compared to plants grown in the 45% light treatment. Illicium henryi failed to survive the 100% light treatment. Illicium lanceolatum and I. parviflorum `Forest Green' were least affected by the 100% light treatment. Severe photooxidative bleaching was noted and confirmed by SPAD and pigment data, although SPAD readings were a poor predictor of total chlorophyll. For taxa of Illicium in our study, photosynthetic gas-exchange parameters and foliage pigment characteristics were improved in the low light treatment, suggesting optimal growth occurs in shaded conditions.

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Acer rubrum `October Glory' has grown well in field studies across the southeastern United States. However, there is limited information on container production for this cultivar. Our objective was to evaluate first-year growth of container-grown `October Glory' at three locations with dissimilar climates in Georgia and Alabama. Rooted cuttings were planted in no. 3 containers at one location in Apr. 1995. Trees were transported the second week of June to Blairsville, Ga.; Auburn, Ala.; and Tifton, Ga. Trees were grown for 6 months until dormant and were harvested at the end of December. Location had no impact on final plant height increase (Blairsville, Auburn, and Tifton, 59.8, 53.0, and 60.2 cm, respectively). Increases in stem diameter and shoot dry mass were greatest at Tifton (8.4 mm, 17.5 g) and least at Blairsville (6.3 mm, 9.2 g), with Auburn similar to both locations (6.8 mm, 12.2 g). Root dry masses and root: shoot ratios were greatest in Tifton (17.2 g, 0.967), with no differences between Blairsville (4.9 g, 0.508) and Auburn (7.0 g, 0.641). Despite climatic dissimilarities, among locations, producers of container-grown `October Glory' could expect similar growth during the first year throughout Georgia and Alabama.

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Japanese-cedar [Cryptomeria japonica (L.f.) D. Don] represents an alternative to leyland cypress [×Cuprocyparis leylandii (A.B. Jacks. & Dallim.) Farjon] as an evergreen screen or specimen plant for landscapes. It performs well under a range of soil and environmental conditions but has been underused attributable, in part, to unsightly winter browning caused by photoinhibition. In previous studies, chance seedlings that did not exhibit winter browning were identified as tetraploids. The current study was conducted to induce polyploidy in japanese-cedar. Approximately 600 seedlings were sprayed with 150 μM oryzalin + 0.1% SilEnergy™ for 30 consecutive days under laboratory conditions. Two hundred thirty-seven seedlings with thickened and twisted leaves were selected, transplanted, and grown in a glasshouse for 120 days. Seedling ploidy levels were analyzed using flow cytometry 180 days after treatment (DAT), identifying 197 (83.1%) tetraploids, 22 (9.3%) cytochimeras, and 18 (7.6%) diploids. Morphology of induced tetraploids was similar to that previously described and provided a phenotypic marker during selection that was over 92% accurate. A random subset of 20 tetraploid individuals was analyzed 270 DAT and were found to contain only tetraploid cells in the leaves analyzed, confirming stability over this period. This study demonstrated the use of oryzalin for inducing tetraploids in japanese-cedar, which we predict will be effective in other gymnosperms.

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