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H. Chris Wien

The stems of many flower species used as cut flowers are too short to be commercially useful. Non-chemical techniques are needed to increase the length of the harvested stems without weakening stem strength. Field experiments were conducted that explored the use of black or red shade fabric, used either as a canopy, or as a side curtain, with three species of cut flowers. Trachelium caerulum, Eustoma grandiflorum (Echo Champagne), and Rudbeckia hirta (Prairie Sun) were grown in split-plot experiments in which shade and shelter treatments were applied as main plots, and the flower species formed the subplots. In 2004, shade canopies of 70% light transmission were compared in black and red (“ChromatiNet”) netting, and 50% red netting. Stem length increased from 51 cm for unshaded controls to 54, 56, and 59 cm for 70% black, red, and 50% red, respectively. Productivity of the plants was decreased an average of 21% by shading. In 2005, shade canopies of 50% black or red were compared to side curtains of the same materials, and an unsheltered control, growing the same species of flowers. Stem length was increased by 25% when plants were grown under a shade canopy, and by 14% in the side curtain plots. Shading treatments reduced stem yield by 31%, whereas side curtains had no significant effect on number of stems per plant. Color of the netting did not affect stem length or stem yield in 2005. In both years, the thickness of harvested stems were increased significantly in the shelter treatments. The three species reacted similarly to the treatments imposed in both years. Shelter treatments can be a practical way of increasing cut flower stem length.

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H. Chris Wien

High tunnels are well suited for use in the production of floral crops, especially cut flowers. Through the increases in temperature afforded at both ends of the growing season, high tunnels allow earlier and later harvests than are possible in the field. During summer, rain protection and a relatively calm environment provides an ideal growing environment to cut flower crops. In U.S. Department of Agriculture (USDA) Hardiness Zones 3 through 5, the higher temperatures of a high tunnel permit culture of warm-season crops like celosia (Celosia argentea) during summer. Cut flower production allows intensive production on a small land area and provides a high level of income. For these reasons, high tunnels have become a standard part of cut flower growers' farms. Most commonly, they are single-bay structures with roll-up sides, but use of multi-bay complexes is becoming more popular for larger-scale growers. In USDA Hardiness Zones of 7 and higher, high tunnels are shaded in summer to lower interior temperatures and enhance production of shade-tolerant species. Overall, techniques of moderating temperature extremes with shading and ventilation, or use of low tunnels inside to increase minimum temperatures are important options for cut flower production. In the presentation, comparisons will be made in growth and earliness of production and yield for several cut flower species grown in the field and an adjacent high tunnel.

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H. Chris Wien

Flowering plants grown and marketed locally as cut flowers have become economically important in recent years, concentrating on species that are too delicate to ship long distances. Although the bulk of this production is done outdoors, extending the season at both ends by using high tunnels (unheated greenhouse structures covered with a single layer of polyethylene), has become popular. To determine the advantages and drawbacks of using high tunnels as season extension structures for cut flowers, variety trials of seven and four flower species were conducted in 2004 and 2005, respectively, both in a high tunnel and in an adjacent field. In the cool, rainy 2004 season, plants in the tunnel were ready for harvest 20 days sooner than the same varieties outside. Outside plants had 25% more stems than tunnel-grown plants, but there was no difference in average stem length. In the dry, warm season of 2005, tunnel-grown plants were 8 days earlier, and had 58% more stems, which were increased in length by 16% over field-grown plants. Lisianthus (Eustoma grandiflorum) and snapdragons (Antirrhinum) were grown in both seasons, and gave similar results both times. Tunnel-grown lisianthus showed a 34% increase in stems per plant, and an 8% increase in stem length, and the stems could be harvested 8 days earlier. Snapdragons were 9 days earlier in the tunnel both years, but tunnel-grown plants produced 22% fewer stems. Disease and insect pressures occurred in both locations, but pest species causing problems differed. With careful choice of species to be grown in tunnels, cut flower production in this environment can be optimized.

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H. Chris Wien and Dale Riggs

Reports of sharply reduced feral bee populations (Apis mellifera) due to harsh winters and prevalence of several bee diseases have raised concerns that pollination and fruit set in pumpkin fields will be adversely affected. In 1995 and 1996, five and eight pumpkin (Cucurbita pepo) fields, respectively, were inventoried on three occasions per season for pollinator activity and percent fruit set. Pollen removal from male flowers was determined visually using a rating scale, while deposition of pollen on stigmata of female flowers was judged by rating fluorescence of pollen on the stigmatic surface under a “black light.” Samples were taken from 15 to 30 locations in each field, and female flowers tagged. These were considered set if they had enlarged to fist size within 14 days. In both years, the amount of pollen remaining on male flowers was negatively correlated with female flower fluorescence ratings. Neither pollen on male flowers nor stigma fluorescence were significantly correlated with percent fruit set. Fifty-two percent of tagged flowers set fruit in both years, with a range of 24% to 84%, and 17% to 78% in 1995 and 1996, respectively. Presence of bee hives in or near the fields had no effect on fruit set. The results indicate that the pollen removal and deposition ratings used were not reliable for predicting fruit set in farmers' fields. In these 2 years, bee hives were not needed in the sampled fields.

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Victor A. Monterroso and H. Chris Wien

The effect of high temperature on abscission of bean (Phaseolus vulgaris L.) flowers and pods was studied under growth chamber and greenhouse conditions. Experiments investigated stages at which flowers are sensitive to heat stress, the period when reproductive structures abscise, and sensitivity of male and female flower parts to heat stress. Heat treatments (2 days at 35C, 10 hours per day) were applied through flower ontogeny, from 8 days before anthesis until anthesis. The flower bud stages were defined by correlating the pedicel length with days to reach anthesis. The prefertilization period showing highest sensitivity to heat stress extended from ≈ 6 days before anthesis to anthesis. We found that 82% of heat-stressed structures abscised as small pods (< 2 cm in length), even when the stress was applied at various flower bud stages. Reciprocal crosses made with pollen from heated plants or on heat-treated flowers indicated that pollen was more affected by heat stress than by female structures.

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Jill A. Montgomery and H. Chris Wien

A study was conducted to compare three sterile, commonly used soil-less media (Agrifoam™ and Oasis™, growth foams, and Grodan™, an expanded rockwool substrate) to determine which media characteristics favor seedling development and establishment in hydroponic systems. These media were studied during days 7–10 of the seed germination stage, when one often observes with the use of foam media the occurrence of “pop-outs,” a disorder in which actively growing roots do not penetrate and spiral on the media surface causing the root tip to die. High percentages of pop-outs cause poor seedling stand, and discourage the use of soilless media for seedling germination. Pop-outs were more frequently observed in Agrifoam (50%) compared to the other media, with Oasis intermediate (15%), and Grodan least affected (>5%). Both physical and chemical characteristics were analyzed to isolate the causes of pop-outs. Oasis and Agrifoam both have higher water retention, and pop-outs increased as the water content of the foam increased. High soluble salts, particularly high magnesium in the root zone, produced roots that were “burned” and did not grow. When magnesium salts in concentrations equivalent to that found in Agrifoam were added to Grodan (control substrate), the number of pop-outs increased. The roots were stunted with little or no root hairs, resembling roots when grown in Agrifoam. We conclude that the high incident of pop-outs in Agrifoam, and to a lesser extent, in Oasis, is caused by high-medium water content and toxic levels of magnesium ions in solution.

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H. Chris Wien and David S. de Villiers

Tipburn is a necrosis of the rapidly expanding young leaves of lettuce, caused by a localized Ca deficiency that is a major constraint to raising productivity of hydroponically-grown leaf lettuce. Root pressure is thought to be important in distributing calcium to young tissue that is not transpiring rapidly in crops such as cabbage, tomato and strawberry. Since root pressure is enhanced by high relative humidity (RH), experiments were conducted with two cultivars of leaf lettuce to determine if regulating relative humidity during the day or night would influence tipburn incidence. Lettuce was grown hydroponically in a glass-covered greenhouse. Plants were transferred to ponds of 1 × 2 m size, starting at about day 25 from sowing. Four ponds containing 42 plants each were subjected to ambient or elevated RH, either during the day, or at night, or at both times. Each pond was covered by a clear polyethylene ventilated canopy, to ensure maintenance of the desired RH condition. The experiment was conducted five times. In three experiments, tipburn developed in 3 or 7 days, depending on the cultivar. The disorder was most severe in ponds whose atmosphere was constantly humid, followed by the treatment that provided humid days and dry nights. Treatments which provided dry conditions, either during the day, or continuously, were least affected. In two experiments, ambient RH rose above 70%, and the differential effect of humidity on tipburn incidence was no longer evident. Both cultivars reacted similarly to the treatments, even though `Winter Density' developed the disorder 4 days before `Batavian'. The results imply that root pressure is less important than transpiration in distributing Ca to the edges of young leaves of leaf lettuce.

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Suzanne Cady Stapleton, H. Chris Wien and Roger A. Morse

Field experiments with six pumpkin cultivars (Cucurbita pepo L.) were conducted in Ithaca, N.Y., in 1992 and 1993 to characterize the patterns of flowering and fruit set. Plants of all cultivars produced the greatest number of female flowers and exhibited the highest rate of fruit set 35-45 days after transplanting, during the first 2 weeks of greatest flower production (“peak bloom”). During the 3 weeks of peak bloom, each plant produced an average of 3.4 pistillate flowers in 1992 and 5.4 in 1993, and fruit set was 50.9% in 1992 and 74.6% in 1993, yielding 1.7 and 4.0 fruit per plant, respectively. In 1994, flower production was further studied with the cultivar Wizard. Flowers were produced in a ratio of 33 staminate to 1 pistillate flower over the entire season. Climatic conditions appeared to be secondary to physiological factors in affecting flowering and fruit set during all three seasons. Characterization of fruit set patterns in pumpkin may aid producers in scheduling pollination services and predicting yields.

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Suzanne Cady Stapleton, H. Chris Wien and Roger A. Morse

Field experiments with six pumpkin cultivars (Cucurbita pepo L.) were conducted in Ithaca, N.Y., in 1992 and 1993 to characterize the patterns of flowering and fruit set. Plants of all cultivars produced the greatest number of female flowers and exhibited the highest rate of fruit set 35-45 days after transplanting, during the first 2 weeks of greatest flower production (“peak bloom”). During the 3 weeks of peak bloom, each plant produced an average of 3.4 pistillate flowers in 1992 and 5.4 in 1993, and fruit set was 50.9% in 1992 and 74.6% in 1993, yielding 1.7 and 4.0 fruit per plant, respectively. In 1994, flower production was further studied with the cultivar Wizard. Flowers were produced in a ratio of 33 staminate to 1 pistillate flower over the entire season. Climatic conditions appeared to be secondary to physiological factors in affecting flowering and fruit set during all three seasons. Characterization of fruit set patterns in pumpkin may aid producers in scheduling pollination services and predicting yields.

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Dominique-André Demers, André Gosselin and H. Chris Wien

Sweet pepper (Capsicum annuum L.) plants were grown under natural or supplemental lighting that extended thephotoperiods to 16, 20, or 24 hours. Increasing the photoperiod to 16 and 20 hours increased pepper plant yields, but continuous light (24 hours) decreased yields compared to the 20-hour photoperiod. In a second experiment, plants were exposed to a photoperiod of 14 or 24 hoursand either pruned to one fruit every four nodes or not pruned. During the first weeks of treatments, plants grown under continuous light had higher shoot mass (fresh and dry) and yields. After 7 to 8 weeks of treatments, plants under continuous light grew more slowly than plants exposed to a 14-hour photoperiod. At the end of the experiment, shoot mass and yields of plants grown under a 14-hour photoperiod were equal to or higher than plants under continuous light. So, it seems possible to provide continuous lighting for a few weeksto improve growth and yields. Limiting the number of fruit per plant increased shoot mass and decreased yields, but had no effect on the general response of pepper plants to photoperiod treatment. Leaf mineral composition was not affected by photoperiod treatment, indicating that reduced growth and yields under continuous light were not due to unbalanced mineral nutrition. Leaf starch and sugar contents were increased under continuous light. However, fruit pruning treatments did not modify the pattern of starch and sugar accumulation under the different photoperiod treatments. Reduced growth and yields measured under a 24-hour photoperiod are probably explained by starch and sugar accumulation in leaves as a result of leaf limitations rather than a sink limitation.