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Natalia K. Hamill, Allan M. Armitage, and Stephanie L. Anderson

As part of the New Floriculture Crop Program at the University of Georgia, a research project was initiated in Fall 2004 to determine the suitability of 12 taxa of woody shrubs for forcing in the greenhouse. In this study, the influence of cooling on greenhouse forcing of (Caryopteris × clandonensis `Sunshine Blue', Leycesteria formosa `Golden Lanterns' and Sambucus nigra `Black Lace') was evaluated. Dormant rooted liners were cooled for 0, 6, or 10 weeks at 1.7 °C to 4.4 °C. With 0 and 6 weeks cooling, Caryopteris never reached an acceptable finish stage. With 10 weeks cooling, plants finished in 7 weeks in the greenhouse. With 0 weeks cooling, Leycesteria was salable in 13 weeks. With 6 and 10 weeks cooling, plants finished in 7 and 8 weeks, respectively. With 0 weeks cooling, Sambucus never reached a salable stage. With 6 weeks cooling, plants were salable in 11 weeks; with 10 weeks cooling, plants finished in 6 weeks. The data suggest that cold is necessary to force Caryopteris and Sambucus in the greenhouse, and that 10 weeks of cold resulted in the shortest production time for both taxa. Data show that 6 weeks cooling of Leycesteria resulted in the shortest production time, but cooling is not necessary. This experiment was repeated in 2005–06 and will be compared to the 2004 findings. Additional experiments conducted in 2006 will also be discussed.

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Allan M. Armitage, James Garner, and Jimmy S. Greer

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Donglin Zhang, Allan M. Armitage, James M. Affolter, and Michael A. Dirr

Lysimachia congestiflora Wils. (Primulaceae) is a new crop for American nurseries and may be used as an annual in the north and a half-hardy perennial in the south. The purpose of this study was to investigate the influence of photoperiod, temperature, and irradiance on its flowering and growth. Three experiments were conducted with photoperiod of 8, 12, 16 hrs day-1, temperature of 10, 18, 26C, and irradiance of 100, 200, 300 μmol m-2s-1, respectively. Plant.9 given long day photoperiod (16 hours) flowered 21 and 34 days earlier, respectively, than plants at 12 sad 8 hour photoperiods. Plants under long day treatment produced more flowers than those at 8 and 12 hours. Plant dry weight did not differ between treatments, but plants grown in the long day treatment produced fewer but larger leaves. Total plant growth increased as temperature increased, but lower temperature (10C) decreased flower initiation and prevented flower development, while high temperature (26C) reduced the longevity of the open flowers. Flowering was accelerated and dry weight increased as plants were subjected to high irradiance levels. The results suggest that Lysimachia congestiflora is a quantitative long day plant. It should be grown under a photoperiod of at least 12 hours at a temperature of approximately 20C. Low light areas should be avoided and supplemental lighting to provide the long days may improve the plant quality.

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Allan M. Armitage*, HazelY. Wetzstein, Stephanie L. Anderson, and Gwen N. Hirsch

Aruncus `Misty Lace is a new hybrid selection between Aruncus dioicus and A. aethusifolius. The plants outstanding characteristics include heat tolerance, dwarf stature, and delicate, plume-like flowers. The objectives of this study were to evaluate the effect of different production parameters (chilling duration, container size, and photoperiod) on flowering in this new genotype Tissue cultured plantlets of Aruncus `Misty Lace' were transplanted to 72- or 36-cell trays and to 10-cm pots. Transplanted materials remained on the greenhouse bench until roots were visible in the soil plug, then placed in a cooler at 2-4 °C for 0 (control), 4, 6, 8, 10 and 12 weeks of chilling. Upon removal, plants were placed in a greenhouse in 10-cm containers under long or short day photoperiods until flowering, or until the experiment was terminated. Plants required less time on the bench to flower as cooling time increased, regardless of container size. Plants flowered earlier under long days than short days, but photoperiod was less of a factor in the control of flowering than cooling duration. Death of plants was greatest in the 72-plug cells and least in 10-cm pots. Plants without well established root growth sustained significant losses, regardless of container size.

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Hazel Y. Wetzstein*, Allan M. Armitage, Gwen N. Hirsch, and Stephanie L. Anderson

Tissue culture is a useful means to clonally propagate new ornamental plant selections, particularly when plant material is limited and/or conventional propagation methods are ineffective. An efficient in vitro multiplication protocol was established to propagate a new goatsbeard hybrid (Aruncus dioicus, × A. aethusifolia). The hybrid is of interest because it exhibits a dwarf habit, delicate white flower panicles and fern-like leaves, yet is tolerant to heat and humidity. Experiments were conducted to evaluate explant type (nodes, stems, leaves, and floral parts), disinfestation procedures, and media formulations including varying concentrations of 6-benzylaminopurine (BAP) and naphthalene acetic acid (NAA). Rapid plant regeneration was obtained with a shoot organogenesis system using a half strength Murashige and Skoog medium supplemented with 4.4 μmol BAP, 0.54 μmol NAA, 30 g·L-1 sucrose, and 3.0 g·L-1 GelGro. Studies compared the performance and yield of plants rooted using different in vitro and ex vitro methods. Ex vitro rooting of shoots during greenhouse acclimatization under mist was most effective. Regenerated plants exhibited uniform and rapid growth, and performed well in greenhouse and field evaluations.