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Pamela M. Lewis, Allan M. Armitage and James M. Garner

Gooseneck loosestrife (Lysimachia clethroides Duby) rhizomes were cooled for 10 weeks at 4 ± 1 °C prior to greenhouse forcing in continuous long days (LD); continuous short days (SD); 4, 6, 8, or 10 weeks of SD followed by LD until anthesis; and 4, 6, 8, or 10 weeks of LD followed by SD. None of the plants grown in continuous SD flowered, and fewer than 30% of plants flowered when grown in 4, 6, or 8 weeks of LD followed by SD for 21 to 25 weeks. At least 10 weeks of LD prior to SD were required to obtain 70% flowering. Plants receiving continuous LD or 4, 6, or 8 weeks of SD followed by LD flowered in the highest percentages (85% to 90%), but only 10% of plants receiving 10 weeks of SD followed by LD flowered. The number of greenhouse days required for visible bud formation and anthesis increased linearly as initial SD exposure increased, but the number of racemes produced by flowering plants was not affected. Plant height was greatest in continuous LD, and decreased linearly as initial SD exposure prior to LD increased from 0 to 10 weeks. Plants grown in continuous SD remained vegetative rosettes throughout the experiment, and their height increased linearly as initial LD prior to SD increased from 0 (continuous SD) to 10 weeks. These results demonstrate that supplemental LD lighting can promote growth and flowering in this species and that lighting can be discontinued 3 weeks before harvest of cut flower crops.

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Pamela M. Lewis, Allan M. Armitage and James M. Garner

The effect of cooling method and duration on off-season cut flower production of Lysimachia clethroides Duby was examined. Rhizomes harvested in October were cooled for 0, 4, 6, 8, 10, or 12 weeks at 4 ± 1 °C in crates with unmilled sphagnum peat moss or in 3.75-L pots filled with a commercial soilless medium prior to forcing in a warm greenhouse. After 6 or more weeks of cooling, shoots emerged from crates in higher percentages than from pots. However, only the duration of cooling, not the method, affected the rate of shoot emergence, visible bud formation, and anthesis of the first bud in the raceme. As cooling increased from 0 to 12 weeks, the greenhouse days required for shoot emergence, visible bud formation, and anthesis decreased linearly. The number of flowering flushes and flowering stems produced per plant varied quadratically with cooling duration, and the highest yields occurred when rhizomes received between 4 and 10 weeks of cooling. High numbers of flowers were produced rapidly after 10 weeks of cooling. As the number of successive flowering flushes increased, the stem length increased linearly while the stem diameter decreased linearly.

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Mark P. Kaczperski, Allan M. Armitage and Pamela M. Lewis

Pelargonium×hortorum L.H. Bailey `Scarlet Elite' seedlings were grown in plugs from seed to transplant size. About 14 days before attaining transplant size, seedlings were exposed to various fertility or temperature regimes (preconditioning treatments), then stored for 1 to 3 weeks at 5C. Seedlings receiving 150 mg N/liter before storage flowered sooner and required less crop time (days to flower – days in storage) than those receiving 0, 75, or 300 mg. Temperature preconditioning at 10 or 15C delayed flowering compared to preconditioning at 20C. Final plant height and dry weight were not adversely affected by varying N levels or temperature during preconditioning. Preconditioning seedlings with 300 mg N/liter resulted in seedling mortality rates up to 16% after 7 days' storage. Low temperature or fertility were not effective preconditioning treatments. Best results were attained by preconditioning seedlings with 150 mg N/liter.

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Mark P. Kaczperski, Allan M. Armitage and Pamela M. Lewis

Seed of Viola × wittrockiana `Majestic Giant Yellow' were germinated in #406 plug trays at ambient CO2, 25 C and a light intensity of 100 μmol s-1m-2 with an 18 hr photoperiod. At emergence and at successive one week intervals, seedlings were exposed to CO2 levels of 500, 1000 or 1500 μl l-1 and irradiances of 100, 225, 350 μmol s-1m-2 for 7 to 35 days, after which seedlings were transplanted into 10 cm pots and grown to flower in the greenhouse. CO2 at 1000 μl l-1 was as effective as 1500 μl l-1 in accelerating growth in the plug stage. 500 μl l-1 at all irradiances did not accelerate growth significantly. Plants grown at 1000 μl l-1 and 225 μmol s-1m-2 intensity reached the 5 leaf stage up to 14 days earlier than the control, as well as decreasing time to flower during the growing on phase.

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Mark P. Kaczperski, Allan M. Armitage and Pamela M. Lewis

Seed of Petunia × hybrida `Ultra White' were germinated in #406 plug trays at 2.5 C and at a light intensity of 100 μ mol s-1m-2 using a 24 or photoperiod. At germination, seedlings were grown under natural light conditions for 8 hrs (SD) or for 8 hrs with the photoperiod extended to 16 hrs (LD) using incandescent bulbs. At approximately the 6th leaf stage, seedlings were stored at 5 C in the dark or at 12 μ mol s-1m-2 and a 24 hr photoperiod for 0 to 21 days. After storage, plants were potted n 10 cm pots and grown to flowering in a greenhouse. Plants grown under SD to the 6th leaf stage with no cold treatment were shorter. flowered later and had more lateral branching than unstored LD plants. Storage at 5 C decreased time to flower of SD plants and increased branching of LD plants regardless of photoperiod during storage.

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Orville M. Lindstrom, Malgorzata A. Florkowska, John Ruter and Pamela Lewis

Seasonal, stem and leaf cold hardiness levels of male and female plants of Ilex purpurea Hassk. and Ilex rotunda var. microcarpa (Lindl. ex Paxton) were determined over two winter seasons. The samples for the cold hardiness studies were taken from established plants growing at the Univ. of Georgia Bamboo Farm and Coastal Gardens in Savannah. Each month, 40 stem cuttings (4 to 5 inches long) were sent by overnight mail for evaluation. The plants were prepared for laboratory freezing exposure tests within 2 h of receiving. The samples were visually evaluated after freezing exposure to estimate their cold hardiness. In general, Ilex purpurea was more cold-hardy than I. rotunda var. microcarpa over both seasons tested, except in midwinter (Jan. 1998 and Feb. 1999) where I. rotunda var. microcarpa was more cold-hardy than I. purpurea. Ilex purpurea attained cold hardiness earlier in the fall and lost its hardiness later in the spring. In general, few consistent differences were observed between the cold hardiness of male and female plants within species.

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George E. Boyhan, Reid L. Torrance, David E. Curry, Pamela M. Lewis, Donna O. Linton and C. Randy Hill

Preplant levels of 5N-4.4P-12.4K (-5S or -9S) and sidedress applications of CaNO3 were evaluated in onion (Allium cepa L.). In addition, high phosphorus fertilizers 18N-20.1P-0K (diammonium phosphate) and liquid 10N-14.8P-0K were evaluated on sites with and without high residual phosphorus levels as well as their interaction with onion cultivars. Sidedress applications of CaNO3 had a significant effect on plant height and an interaction with preplant 5N-4.4P-12.4K fertilizer. There was a linear increase in plant height with increasing applications of 5N-4.4P-12.4K from 0 to 1569 kg·ha-1 with the CaNO3 applications. Neither 5N-4.4P-12.4K nor CaNO3 applications affected stand count. 5N-4.4P-12.4K fertilizer had significant linear effects on tissue potassium and sulfur. Tissue nitrogen and calcium increased with CaNO3 applications while phosphorus, potassium, and sulfur decreased. CaNO3 also had a positive effect on suitability for transplanting. There was an interaction effect between 5N-4.4P-12.4K and CaNO3 for tissue phosphorus levels. There was a linear decrease in tissue phosphorus levels with increasing amounts of 5N-4.4P-12.4K fertilizer with the sidedress CaNO3 treatments. High phosphorus fertilizers applied directly after seeding had no effect on plant stand or plant height either on soils with or without high residual phosphorus in 1998. In 1999, 10N-14.8P-0K fertilizer had a significant effect on plant height while 18N-20.1P-0K did not. Based on this study, we conclude that additional applications of high phosphorus fertilizers applied post seeding are not required due to the relatively warm conditions found in southeast Georgia in September. There were differences between cultivars, but cultivar× high phosphorus fertilizer interactions were nonsignificant.

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George E. Boyhan, William M. Randle, Albert C. Purvis, Pamela M. Lewis, Donna O. Linton, Reid L. Torrance and David E. Curry

A 3-year study on the effects of growth stimulants on yield, bulb size, bulb quality, and storability of short-day onions (Allium cepa L.) was conducted at three locations. Treatments included 2-hydroxypropanoic acid, humic acids, humic acids in conjunction with micronutrients, and two formulations of cytokinin applied as a transplant dip and/or plant spray. There were no differences between 2-hydroxypropanoic acid and an untreated check at two different farm locations for onion yield, equatorial bulb diameter, or percent jumbos [≥3 inches (≥7.6 cm)] in 1997. Comparisons between untreated checks, 2-hydroxypropanoic acid, humic acids as a transplant dip or plant spray, and humic acids with micronutrients, all applied as transplant dip or plant spray, indicated there were no differences among treatments for yield, pungency, soluble solids, equatorial bulb diameter, or percent marketable bulbs after 6 months in controlled atmosphere storage in 1997-98. In a final experiment, these treatments were evaluated in a factorial arrangement using the short-day onion cultivar Pegasus and a mixture of cultivars WI-609 and WI-3115, which are referred to as Wannamaker cultivar mix. `Pegasus' displayed higher yield and lower soluble solids than the Wannamaker cultivar mix. Treatment with humic acids and micronutrients, or cytokinins resulted in greater percent marketable bulbs after 4.5 months of controlled atmosphere storage compared to the untreated check. No differences were observed among the treatments for pungency or bulb size. In addition, there was no treatment by cultivar interaction.