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  • Author or Editor: John Ruter x
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A study was conducted with Coreopsis verticillata L. `Moonbeam' and Plumbago auriculata Lam. to evaluate the growth of these perennial plants in 2.6-liter (#1) black plastic containers (BPCs) compared to plants grown in fiber containers with Cu(OH)2 (FCs+) impregnated into the container walls. Coreopsis root and shoot dry weight was unaffected by container type, whereas Plumbago root and shoot dry weight was greater (2.2× and 1.6×, respectively) for plants grown in FCs+ compared to BPCs. The root : shoot ratio of Plumbago increased 30% when plants were grown in FCs+ compared to BPCs. Root circling was effectively controlled for both species grown in the FCs+. FCs remained in salable condition for the duration of the study. In contrast to untreated FCs, FCs+ will have to be removed at transplanting to allow for normal root development.

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Paclobutrazol was applied as a foliar spray, root-medium drench, and impregnated spike to `New Gold' lantana grown in 2.8-liter pots. Plants were treated 14 June 1993 at rates of 0, 0.5, and 1.0 mg a.i. paclobutrazol/pot and were harvested 27 July 1993 when control plants required further pruning. Impregnated spikes reduced plant size and flowering to a greater degree than spray applications. Drenches reduced root dry weight and biomass compared to spray applications. Plants treated with 0.5 and 1.0 mg a.i. paclobutrazol/pot were not different in regards to plant growth and flowering. Compared to nontreated controls, plants treated with paclobutrazol had a reduced growth index, decreased shoot and root dry weight, and fewer flowers with open florets. All plants in the study were marketable, even though growth control was considered excessive. Lower rates than used in this study should be considered for controlling growth. These results suggest that impregnated spike formulations of paclobutrazol may control plant growth in pine bark-based media.

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Carolina laurel cherry (Prunus caroliniana) is native to the U.S. southeastern coastal plain from North Carolina westward to eastern Texas. The species has been planted extensively in the southeast as an ornamental tree or hedge. Unfortunately, carolina laurel cherry naturalizes readily and is now found in a variety of habitats, both natural and disturbed. Flowering occurs in the late winter/early spring before new leaves emerge and fruit ripens in the fall/winter. Fruit is eaten by migratory birds and seed is dispersed. Seedlings readily germinate in the understory of forests and landscapes in the spring. As there are a limited number of cultivars available, selections with improved form and sterility are needed for the landscape trade. In 2008, seed was collected and treated with Cobalt-60 gamma irradiation at rates ranging from 0 to 150 Gy. The lethal dose killing 50% of the seedlings (LD50) was between 50 and 100 Gy. Three sterile plants were selected in 2012 from the M1 (first generation of mutagen-treated seedlings) population totaling 62 seedlings. M2 (second-generation seedlings from M1 parents) seed was collected Fall 2012, and 1509 seedlings were grown to flowering size in containers. In 2014–15, 120 seedlings that showed no fruit production were planted in the field in Watkinsville, GA, for further evaluation. Ratings on field-grown plants in Dec. 2017 and 2018 showed that 73% and 78% of the plants, respectively, produced no fruit, whereas the remaining plants had minimal to heavy fruit set. Because carolina laurel cherry is andromonoecious, production of male and bisexual flowers was evaluated on 17 selections in 2018. Of 500 flowers evaluated per selection, the number of male flowers per plant ranged from 22 to 415 (4.4% to 83%). The number of racemes with all-male flowers on each selection ranged from 1 to 32. There were no significant correlations between the number of male flowers or number of all-male flowered racemes per plant and production of fruit. Approximately 5% of M2 seedlings remain seedless after 6 years of growth.

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In 1991, a cooperative project with the U.S. National Arboretum in Washington, D.C., was initiated in Tifton, Ga. (USDA hardiness zone 8a) to evaluate red maples (Acer rubrum L.) potentially suitable for the coastal plain region of the southeastern U.S. Greatest annual height growth across all cultivars over 6 years was for `Alapaha', a seedling selection from southern Georgia with annual height growth of 35 inches (88.0 cm), and several seedling selections from northern Florida with annual height increases in excess of 33 inches (86.0 cm). Selections showing the least average annual height growth were NA-56024 and NA-57772 (`Red Rocket'). For commercially available cultivars, the most dependable for fall color in Tifton was `October Glory'®. In addition, two new selections from the National Arboretum have also shown excellent fall color—`Somerset' and `Brandywine'.

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Swamp sunflower (Helianthus simulans) is an underused perennial plant native to the southeastern United States that produces an abundance of golden yellow inflorescences in the fall. It is a vigorous grower and tolerates a wide variety of soil conditions, growing in wetland and nonwetland habitats. Swamp sunflower warrants wider use in perennial beds and landscapes, and research on production practices to make plants more suitable for shipping could promote its production. This study evaluated the effects of plant growth regulators (PGRs) on the growth and floral attributes of the swamp sunflower. Treatments were applied to rooted cuttings in 1-gal pots as a substrate drench of 1, 2, 4, or 6 mg/pot paclobutrazol; 0.5, 1, 2, or 4 mg/pot flurprimidol; or water (control)/pot for Expt. 1. A second experiment (Expt. 2) applied 4, 6, or 8 mg/pot paclobutrazol; 2, 4, or 6 mg/pot flurprimidol; or water (control)/pot. Six weeks after treatment (WAT) for Expt. 1, paclobutrazol applied at 4 and 6 mg/pot and flurprimidol at 2 and 4 mg/pot resulted in smaller plants (as reflected by growth index) by 29%, 34%, 22%, and 48%, respectively, compared with the control. Furthermore, at the termination (6 WAT) of Expt. 1, the highest rate of flurprimidol produced the smallest plants, with the exception of the highest rate of paclobutrazol. By 6 WAT, plants treated with the highest rate of paclobutrazol and flurprimidol had lower dry weights and higher chlorophyll measurements than control. All PGR treatments for Expt. 2 resulted in smaller plants than the control by 27% to 36% at 4 WAT and 23% to 41% at 6 WAT. Differences for internode length and flower diameter were observed for Expts. 1 and 2, respectively. Results from these experiments suggest a substrate drench application of 6 mg/pot paclobutrazol or 4 mg/pot flurprimidol can be used for producing smaller plants compared with nontreated plants for swamp sunflower under greenhouse conditions.

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The effect of container design on physical parameters of media with different bulk densities was evaluated. A significant interaction between container design and media for water-holding capacity and air space was found. A container with a polyester fabric bottom had the largest media air space and the smallest water-holding capacity after 24 h of drainage when placed on a column of sand to allow for free drainage from the container medium. For the media tested, a blend of composted pine bark and hardwood bark (PB:HB) appeared to have good physical characteristics for a container medium in the container designs that were evaluated. Container design should be considered when selecting a container medium because physical parameters of a given medium will be influenced.

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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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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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Water quality and quantity are increasingly important concerns for agricultural producers and have been recognized by governmental and nongovernmental agencies as focus areas for future regulatory efforts. In horticultural systems, and especially container production of ornamentals, irrigation management is challenging. This is primarily due to the limited volume of water available to container-grown plants after an irrigation event and the resultant need to frequently irrigate to maintain adequate soil moisture levels without causing excessive leaching. To prevent moisture stress, irrigation of container plants is often excessive, resulting in leaching and runoff of water and nutrients applied to the container substrate. For this reason, improving the application efficiency of irrigation is necessary and critical to the long-term sustainability of the commercial nursery industry. The use of soil moisture sensing technology is one method of increasing irrigation efficiency, with the on-farm studies described in this article focusing on the use of capacitance-based soil moisture sensors to both monitor and control irrigation events. Since on-farm testing of these wireless sensor networks (WSNs) to monitor and control irrigation scheduling began in 2010, WSNs have been deployed in a diverse assortment of commercial horticulture operations. In deploying these WSNs, a variety of challenges and successes have been observed. Overcoming specific challenges has fostered improved software and hardware development as well as improved grower confidence in WSNs. Additionally, growers are using WSNs in a variety of ways to fit specific needs, resulting in multiple commercial applications. Some growers use WSNs as fully functional irrigation controllers. Other growers use components of WSNs, specifically the web-based graphical user interface (GUI), to monitor grower-controlled irrigation schedules.

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In five experiments, singlenode cuttings of `Red Cascade' miniature rose (Rosa) were treated with a basal quick-dip (prior to insertion into the rooting substrate) or sprayed to the drip point with a single foliar application (after insertion) of Dip `N Grow [indole-3-butyric acid (IBA) + 1-naphthaleneacetic acid (NAA)], the potassium salt of indole-3-butyric acid (K-IBA), or the potassium salt of 1-naphthaleneacetic acid (K-NAA); a single foliar spray application of Dip `N Grow with and without Kinetic surfactant; or multiple foliar spray applications of Dip `N Grow. Spray treatments were compared with their respective basal quick-dip controls {4920.4 μm [1000 mg·L-1 (ppm)] IBA + 2685.2 μm (500 mg·L-1) NAA, 4144.2 μm (1000 mg·L-1) K-IBA, or 4458.3 μm (1000 mg·L-1) K-NAA}. Cuttings sprayed with 0 to 246.0 μm (50 mg·L-1) IBA + 134.3 μm (25 mg·L-1) NAA, 0 to 207.2 μm (50 mg·L-1) K-IBA, or 0 to 222.9 μm (50 mg·L-1) K-NAA resulted in rooting percentages, total root length, percent rooted cuttings with shoots, and shoot length similar to or less than control cuttings. Exceptions were cuttings sprayed with 0 to 2.23 μm

(0.5 mg·L-1) K-NAA, which exhibited shoot length greater than the control cuttings. Addition of 1.0 mL·L-1 (1000 ppm) Kinetic organosilicone surfactant to spray treatments resulted in greater total root length and shoot length. Repeated sprays (daily up to seven consecutive days) had no or negative effects on root and shoot development.

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