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James M. Garner, Starla A. Jones, and Allan M. Armitage

Two studies were conducted to determine the influence of decapitation (pinch treatment) and photoperiod treatments on stem length, days from planting to harvest, and flowering stem yield in two delphinium cultivars. Plants of Delphinium ×belladonna Hort. ex Bergmans `Völkerfrieden' received a hard pinch (removal of apex and all stem and leaf tissue associated with leaves ≤10 cm), soft pinch (removal of apex and all stem and leaf tissue associated with leaves ≤4 cm), or no pinch. Plants of the D. elatum L. `Barbara' series were grown under either long- or short-day photoperiod, each treatment with or without receiving a soft-pinch. Time from planting to harvest was longer in pinched plants than in nonpinched plants of both cultivars regardless of photoperiod. Flowering stems were longer in hard- and soft-pinched plants of `Völkerfrieden' compared to nonpinched plants, and with `Barbara', stem length of pinched plants was either longer or similar to that of nonpinched plants regardless of photoperiod. At 30 days after the commencement of harvest, yield of flowering stems for hard-pinched plants of `Völkerfrieden' was higher than that for nonpinched plants, but yield from soft-pinched plants was similar to that for those not pinched. Stem yield for `Barbara' was higher for pinched plants under the long-day photoperiod, but under short days, yield from pinched plants was similar to that for those not pinched. Long days appear to increase yield and reduce production time in delphinium cultivars. Commercial benefits may be realized by growing nonpinched plants for earliness and pinched plants for longer stems and higher yield.

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Jessica Phillips, James M. Garner, and Allan M. Armitage

Five taxa of Helichrysum Mill. and Brachycome Cass. were recently evaluated for greenhouse production and amenity use. Preliminary studies on the influence of photoperiod, temperature, and growth regulators were conducted for H. bracteatum Vent., (syn Bracteantha bracteata) `Sunray' and `Matilda Yellow', H. apiculatum D.C, (syn Chrysocephalum apiculatum) `Golden Buttons' and Brachycome iberidifolia Benth. `Jumbo Mauve' and `Mauve Delight'. All taxa of Helichrysum were quantitative LD plants, flowering slightly more rapidly under night-break (2200-0200 HR) and extended day incandescent lighting, compared with 9-h short-day treatment. No influence of photoperiod occurred with cultivars of Brachycome. Constant temperature of 12, 20, or 28 °C were provided and all taxa demonstrated a linear decrease in flowering time as temperatures increased. The growth index (average of height and two measurements of width) was also influenced by temperature. Paclobutrazol and daminozide were applied at different concentrations and frequencies. Paclobutrazol was more effective than daminozide in both genera, and daminozide was ineffective in Brachycome.

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Amanda M. Miller, Marc W. van Iersel, and Allan M. Armitage

Light and temperature responses of whole-plant CO2 exchange were determined for two cultivars of Angelonia angustifolia Benth., `AngelMist Purple Stripe' and `AngelMist Deep Plum'. Whole crop net photosynthesis (Pnet) of `AngelMist Purple Stripe' and `AngelMist Deep Plum' were measured at eight temperatures, ranging from 17 to 42 °C. Pnet for both cultivars increased from 17 to ≈20 °C, and then decreased as temperature increased further. Optimal temperatures for Pnet of `AngelMist Purple Stripe' and `AngelMist Deep Plum' were 20.8 and 19.8 °C, respectively. There was no significant difference between the two cultivars, irrespective of temperature. The Q10 (the relative increase with a 10 °C increase in temperature) for Pnet of both cultivars decreased over the entire temperature range. Dark respiration (Rdark) of both cultivars showed a similar linear increase as temperature increased. As photosynthetic photon flux (PPF) increased from 0 to 600 μmol·m-2·s-1, Pnet of both cultivars increased. Light saturation was not yet reached at 600 μmol·m-2·s-1. The light compensation point occurred at 69 μmol·m-2·s-1 for `AngelMist Purple Stripe' and at 89 μmol·m-2·s-1 for `AngelMist Deep Plum'. The lower light saturation point of `AngelMist Purple Stripe' was the result of a higher quantum yield (0.037 mol·mol-1 for `AngelMist Purple Stripe' and 0.026 mol·mol-1 for `AngelMist Deep Plum'). The difference in quantum yield between the two cultivars may explain the faster growth habit of `AngelMist Purple Stripe'.

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Raymond Kessler, Allan M. Armitage, and David S. Koranski

Plug flats of Begonia × semperflorens-cultorum Hort. `Pizzazz Red', Vodka', and `Viva' were provided 0, 50, 125, or 200 μmol·s-1·m-2 metal-halide supplemental irradiance in the greenhouse for 0, 2, 4, 6, or 8 weeks. Treatments were initiated when seedlings were in the first true leaf stage (2 weeks after sowing). Plug-grown begonias reached transplantable dry weight and leaf area after 4 weeks of 125 μmol·s-1·m-2 supplemental exposure, while those under O and 50 μmol·s-1·m-2 required 6 to 8 weeks. Fewest number of days to visible bud and anthesis and the fewest number of nodes for all cultivars occurred after 2 weeks of 125 μmol·s-1·m-2 supplemental exposure. The same conditions achieved the greatest final leaf area and plant height; however, final dry weight was unaffected. Additional supplemental irradiance and/or exposure time did not accelerate flowering or improve vegetative growth of finished plants.

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Julie A. Plummer, T. Eddie Welsh, and Allan M. Armitage

Zantedeschia aethiopica (L.) K. Spreng. `Childsiana' is a dwarf white calla lily with potential for pot culture. Nine stages of flower development from macrobud to senescence were described and shelf life under a low-light postproduction environment was examined. Flowers at the macrobud stage opened in the postproduction environment. Plants with flowers at the macrobud stage (Stage 1) and plants with spathes fully opened but before pollen shed (Stage 5) had shelf lives of 26 and 11 days, respectively.

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Brian P. Gibbons, Timothy J. Smalley, and Allan M. Armitage

Three biostmulants, Grow-plex (Menefee Mining Corp., Dallas, Texas), Roots 2 (LISA Product Corp., Independence, Mo.), and Root n' Shoot (Natural Organic Products International, Mount Dora, Fla.) were applied to transplanted plugs of Salvia splendens `Empire Red' and Begonia semperflorens-cultorum `Varsity Pink' and `Varsity Brite Scarlet'. Root n' Shoot drench (0.78%) solutions at transplant increased root weight, but a 1.56% solution decreased root weight of salvia; however, shoot growth was unaffected. Root n' Shoot decreased shoot growth of begonia, but did not affect root growth of begonia. Roots 2 treatments (0.25% or 2.00%) increased shoot weight of salvia, but did not affect salvia root growth or root or shoot growth of begonia. Spraying Grow-plex (0.78% or 1.56%) to runoff at transplanting and 2 weeks after transplanting did not affect root or shoot growth of salvia or begonia.

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Brian P. Gibbons, Timothy J. Smalley, and Allan M. Armitage

Three biostimulants, Grow-plex (Menefee Mining Corp., Dallas), Roots 2 (LISA Product Corp., Independence, Mo.), and Root n' Shoot (Natural Organic Products International, Mount Dora, Fla.) were applied to transplanted plugs of Salvia splendens `Empire Red' and Begonia semperflorens `Varsity Pink' and `Varsity Brite Scarlet'. Root n' Shoot drench (0.78%) solutions at transplant increased root weight, but a 1.56% solution decreased root weight of Salvia, although shoot growth was unaffected. Root n' Shoot decreased shoot growth of Begonia, but did not affect root growth. Roots 2 treatments (0.25% or 2.00%) increased shoot weight of Salvia, but did not affect the root growth of Salvia or the root or shoot growth of Begonia. Spraying Grow-plex (0.78% or 1.56%) to runoff at transplanting and 2 weeks after transplanting did not affect root or shoot growth of Salvia or Begonia.

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Allan M. Armitage, Linda Copeland, Paula Gross, and Meg Green

Rhizomes of Oxalis adenophylla Gillies and bulbs of Ipheion uniflorum Raf. were planted and wet- or dry-stored at 5 °C for 0, 6, 10, 14, or 18 weeks, before being placed in a greenhouse. Regardless of moisture regime, foliage emergence and time to flower decreased for both species with increasing duration of cooling. Wet-stored bulbs/rhizomes within a cooling treatment required less time to foliage and flower emergence when compared with the corresponding dry-storage period. About 10 weeks of 5 °C was optimum for both species.

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Allan M. Armitage, N. H. Hamill, and S. Anderson

Research to determine protocols for greenhouse forcing of woody shrubs was initiated as part of the New Crop Research program at the University of Georgia. About 15 woody taxa were initially selected for the program based on habit, foliar qualities and flowering (if present). All plants were subjected to 1.7–4.4 °C for 0, 6, or 10 weeks in a controlled temperature cooler. Based on growth and visual characteristics, Leptodermis oblonga, Indigofera pseudotinctoria `Rose Carpet', Forsythia ×intermedia `Golden Peep' and Philadelphus coronaria `Manteau d'Hermaine' was discarded. Caryopteris x clandonensis `Sunshine Blue', Leycesteria formosa `Golden Lanterns', Sambucus nigra`Black Lace', Philadelphus coronaria`Variegata' and Physocarpus oblongifolius `Summer Wine' were investigated further. Data presented for Physocarpus suggested that cooling was not necessary for growth; however, 10 weeks of cooling resulted in the least time to finish in the greenhouse. Ten, six, and zero weeks cold resulted in 17, 10, and 7 weeks finish time respectively. Additional work conducted in 2005 and future research will be discussed.

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Allan M. Armitage, Natalia K. Hamill, 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 woody shrubs for forcing in the greenhouse. This paper will provide an overview of the research, indicating plants that were determined to be suitable for greenhouse forcing and sales in the retail area and those that were discarded from the program. About 15 taxa were initially selected for the program based on habit, foliar qualities, and flowering (if present). All plants were subjected to 1.7 °C to 4.4 °C for 0, 6, or 10 weeks in a controlled temperature cooler. Based on growth and visual characteristics, Leptodermis oblonga, Indigofera pseudotinctoria `Rose Carpet', Forsythia × intermedia `Golden Peep', and Philadelphus coronaria `Manteau d'Hermaine' were discarded. Caryopteris × clandonensis `Sunshine Blue', Leycesteria formosa `Golden Lanterns', Sambucus nigra `Black Lace', Philadelphus coronaria `Variegata', and Physocarpus oblongifolius `Summer Wine' were investigated further. Data presented for Physocarpus suggested that cooling was not necessary for growth; however, 10 weeks of cooling resulted in the least time to finish in the greenhouse. Zero, 6, and 10 weeks cold resulted in 17, 10, and 7 weeks finish time, respectively. Additional work on Kolkwitzia, Buddleia, and Wegelia conducted in 2005 and future research will be discussed.