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  • Author or Editor: A. M. Armitage x
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Achillea millefolium `Summer Pastels' is a qualitative long-day plant with a critical photoperiod between 12 and 16 hours at 18C. Plants grown under a 16-hour photoperiod flowered after 27 days, while those under 8 hours remained vegetative. Shoot dry weight was not affected by photoperiod. Low temperature (10C) delayed the time of flower bud formation and anthesis by ≈20 days. Low irradiance (100 μmol·m–2·s–1) delayed flowering and resulted in lower shoot dry weight, while moderate shading (200 μmol·m–2·s–1) did not significantly affect flowering time and growth compared with high irradiance levels (300 μmol·m–2·s–1).

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Abstract

Two applications of 3500 ppm daminozide applied 4 to 5 weeks from sowing and at visible bud stage resulted in excellent height control of Calendula officinalis L. ‘Mandarin’ by reducing both peduncle and internodal elongation. There were no differences in flowering time between any daminozide concentrations (1500, 3500, or 5000 ppm) and control. Light reduction of 50% during the spring months did not increase plant height or prolong flowering times compared with ambient, but 75% light reduction increased internode elongation and duration of flowering. There were no interactions between light reduction and number of daminozide applications. Chemical name used: butanedioic acid mono(2,2-dimethylhydrazide) (daminozide).

Open Access

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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As part of the New Floriculture Crop Program at the University of Georgia, a research project was initiated in Fall 2004 to determine production protocols for forcing woody shrubs in the greenhouse. The influence of cooling on greenhouse forcing of three woody taxa (Caryopteris ×clandonensis `Sunshine Blue', Leycesteria formosa `Golden Lanterns' and Sambucus nigra `Black Lace') was evaluated. Dormant rooted liners (7 cm) were received in November 2004 and were cooled for 0, 6, or 10 weeks at 1.7–4.4 °C. With 0 weeks cooling, Caryopteris ×clandonensis `Sunshine Blue' never reached an acceptable finish stage. With 6 weeks cooling, plants were not of sufficient quality to be saleable; however with 10 weeks cooling, plants finished in 7 weeks in the greenhouse. With 0 weeks cooling, Leycesteria formosa`Golden Lanterns' was saleable in 13 weeks. With 6 weeks cooling, plants finished in 7 weeks. With 10 weeks cooling, plants finished in 8 weeks. With 0 weeks cooling, Sambucus nigra `Black Lace' never reached a saleable stage. With 6 weeks cooling plants were saleable in 11 weeks; with 10 weeks cooling plants finished in 6 weeks. The data suggest that cold is necessary for greenhouse forcing of Caryopteris and Sambucus, and that 10 weeks of cold resulted in the shortest production time. Data suggest that 6 weeks cooling of Leycesteria resulted in the shortest production time; however cooling is not necessary to produce a finished plant of good quality.

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Abstract

Flowering time, dry weight, total leaf area, and vegetative height of Tagetes patula L. were predicted on the basis of day temperature, night temperature, and quantum flux density (QFD). High temperatures (30°C) decrease flowering time regardless of QFD and greatest leaf surface area was caused by high QFD. As night temperatures increased, maximum leaf area occurred at lower day temperatures than those necessary for fastest flowering time. Each response was characterized by response surface technique.

Open Access

Abstract

Flower petal abscission (shattering) in seed geraniums (Pelargonium X hortorum Bailey) is delayed by low temperature (1-5°C) and ethylene-free air. Naphthaleneacetic acid (NAA) or CO2 (5%) did not delay shattering. Respiration and endogenous ethylene synthesis did not follow a climacteric pattern. A method was devised to test flowers for petal abscission. Variation in petal abscission was found among flowers of 35 cultivars evaluated over a 2-year period.

Open Access

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.

Free access

Abstract

The relationships of net photosynthesis (Pn) to soil water potential, leaf diffusive resistance, leaf water potential, and relative water content were studied with hybrid geranium (Pelargonium × hortorum Bailey cv Sprinter Scarlet) grown under conditions of greenhouse pot culture. Net photosynthesis went through 4 stages according to the effects of water stress on the plants. As water stress increased, Pn went from a steady-state maxiumum rate to slow decline, to rapid decline, to total inhibition. During rapid Pn decline, soil water potential rapidly decreased from −4 bars to −14 bars, and leaf diffusive resistance increased from 4 s cm−1 to 80s cm−1. Leaf water potential was −7 bars, and relative leaf water content was 81–87%. Leaf water potential appeared to be the best indicator of imminent Pn decline. After rewatering water-stressed plants, 3 days were required to elevate Pn to a steady-state maximum which was only 90% of initial steady-state Pn.

Open Access

Abstract

Growth and flowering of Pelargonium × hortorum Bailey cvs. Sprinter Scarlet, Sprinter White, and Ringo were associated with cumulative photosynthetically active radiation (PAR); 41-65% of the variability in days to flower was attributed to cumulative PAR. Vegetative and total plant height decreased as cumulative PAR increased. The number of lateral breaks increased as irradiance increased while fresh weight showed no consistent pattern.

Open Access

Abstract

Flowering time, plant height and weight of Zinnia elegans Jacq were reduced by 4 weeks of 9 hour photoperiods. Multiple application of butanedioic acid mono-2, 2 dimethyl-hydrazide (daminozide) reduced plant height and flower diameter but increased time to flower without affecting fresh weight while ancymidol restricted height and fresh weight but not time to flower.

Open Access