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  • Author or Editor: Todd Cavins x
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Anti-gibberellin plant growth regulators (PGRs) not only affect cell elongation, but other biochemical processes. The experimental PGR A-1699 DF was evaluated for efficacy of height and width control as well as effect on flower petal pigmentation. While the active ingredient in A-1699 DF has proven effective for height control on several crops, that was not observed on Impatiens `Accent Cranberry' in this study. However, A-1699 DF did affect flower petal pigmentation. A-1699 DF likely inhibited anthocyanin production that resulted in light pink versus cranberry flower petals observed on the control, Paczol, and B-Nine/Cycocel PGR applications.

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Silicon (Si) is a nonessential element that has proven to be a beneficial supplement to agricultural crops. In floriculture greenhouse production, soilless substrates have limited Si content and supplements may improve plant quality. The objective of this study was to determine Si sources, rates, and application methods to improve plant quality. Zinnia elegans `Oklahoma Formula Mix', Helianthus annuus `Ring of Fire', and Gerbera `Acapella' were provided potassium silicate (KSiO3) as a media incorporated flakes or weekly drench, sodium silicate (NaSiO3) as weekly foliar spray or ashed rice hulls. Zinnia and Helianthus Si levels were highest in leaf (0.5% to 1.7%), followed by flower (0.3-0.5%) and stem (0.2-0.4%) tissues. Gerbera accumulated lower amounts of Si compared to Zinnia and Helianthus with similar leaf and flower content values ranging from 0.4% to 0.6% with stem values 0.4% Si. Depending on source and rate, several horticultural traits were improved. Zinnia benefits included stem thickness, increase in flower diameter and stem erectness. Helianthus Si supplementation resulted in increased stem thickeness and flower diameter. However, phytotoxicity problems occurred with Si rates above 200 mg·L–1 (SiO2 applied as weekly potassium silicate drench). Gerbera stems thickened with KSiO3 and NaSiO3 applications, but NaSiO3 foliar sprays increased stem length, flower diameter and resulted in earlier flowering.

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Silicon (Si) is a beneficial element to many agricultural crops. We found improved horticultural traits in our preliminary Si supplementation research on floricultural greenhouse crops produced in soilless substrates. The objective of this study was to establish optimum Si rates based on previous results and investigate the relationship of Si tissue and substrate content. Potassium silicate (KSiO3) weekly drenches (0, 50, 100, 150 mg·L-1 SiO2), media-incorporated KSiO3 flakes (0, 280, 400, 520 g·m-3 SiO2), and ashed rice hulls (0, 200, 270, 360 g·m-3 SiO2) were provided to Helianthusannuus`Ring of Fire'. Leaf, stem, and flower tissues as well as soilless substrate samples were collected for Si analysis. Several Si treatments resulted in plants with increased flower and stem diameter compared to untreated controls (P ≤ 0.05). Weekly drenches with KSiO3 (150 mg·L-1 SiO2), KSiO3 flakes (280 g·m-3 SiO2), and ashed rice hulls (360 g·m-3 SiO2) were the most efficient treatments based on the increased quality characteristics. Leaf tissue had the highest Si content, followed by flower, then stem tissue. Correlation analysis indicated that leaf and flower Si content was positively correlated with saturated media extract substrate samples (correlation coefficients r= 0.75 and 0.63, respectively).

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Campanula medium L. `Champion Blue' and `Champion Pink' and Lupinus hartwegii Lindl. `Bright Gems' were grown in 8- or 16-h initial photoperiods, transplanted when 2-3, 5-6, or 8-9 true leaves developed, and placed under 8-, 12-, or 16-h final photoperiods. The lowest flowering percentage for `Champion Blue' (<1%) and `Champion Pink' (16%) resulted from plants grown in the 8-h photoperiod continuously. One hundred percent flowering occurred when Campanula were grown in the 16-h final photoperiod, indicating that `Champion Blue' and `Champion Pink' are long-day plants. Plants grown initially in the 8-h and finished in the 16-h photoperiod had the longest stems. Stem diameter was generally thickest for plants grown in the 8-h compared with the 16-h initial photoperiod. However, the 8-h initial photoperiod delayed anthesis compared with the 16-h initial photoperiod. `Champion Blue' and `Champion Pink' plants transplanted at the 2-3 leaf stage from the 16 hour initial to the 8-h final photoperiod had flowering percentages of 64% and 63%, respectively; however, when transplanted at the 8-9 leaf stage, plants were fully mature and 100% flowering occurred indicating that all plants were capable of flowering. In year 2, plants receiving high intensity discharge (HID) supplemental lighting during the 16-h initial photoperiod reached anthesis in 11 fewer days compared with plants not receiving HID supplemental lighting. High profits were obtained from Campanula grown in the 8-h initial photoperiod and transferred at 5-6 true leaves into the 16-h final photoperiod. Lupinus hartwegii plants had a high flowering percentage (96% to 100%) regardless of photoperiod or transplant stage. The 16-h final photoperiod decreased days to anthesis compared with the 8- or 12-h final photoperiod indicating that L. hartwegii is a facultative long-day plant. Increasing length of final photoperiod from 8- to 16-h increased stem length. Juvenility was not evident for Lupinus in this study. In year 2, Lupinus cut stems were generally longer and thicker when given HID supplemental lighting, especially when grown in the 8- or 12-h final photoperiod. Supplemental lighting also reduced days to anthesis. Highest profits were generally produced from Lupinus plants grown with supplemental HID lighting (during the initial photoperiod) until 8-9 true leaves had developed.

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Hyacinthoides hispanica (Mill.) Roth., Hyacinthus orientalis L. `Gypsy Queen', Narcissus pseudonarcissus L. `Music Hall', N. pseudonarcissus `Tahiti', Tulipa gesneriana L. `Couleur Cardinal', and T. gesneriana `White Emperor' bulbs were given 0 or 6 weeks of preplant 5 °C cold treatment and planted 15, 30, or 45 cm deep into raised ground beds under 0%, 30%, or 60% shade. Plant growth was monitored for 2 years after planting. Preplant 5 °C cold pretreatment reduced percentage of Tulipa `White Emperor' bulbs that flowered but did not affect the percentage of bulbs that flowered for the other species. Cold pretreatment also delayed anthesis in one or both years for all cultivars except Hyacinthoides hispanica. The greatest percentage of bulbs flowered when planted 15 cm deep. The 45-cm planting depth reduced bulb flowering percentage or eliminated plant emergence. Increasing planting depth increased days to anthesis for all cultivars in both years. Increasing shade increased stem lengths in year 2 for all cultivars except Hyacinthoides hispanica, but did not influence percentage of bulbs flowering for any cultivars. For all cultivars perennialization was low regardless of treatment as less than 30% of bulbs survived to the 2nd year.

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Campanula medium L. `Champion Blue' (CB) and `Champion Pink' (CP) and Lupinus hartwegii Lindl. `Bright Gems' (LH) were grown in 8- or 16-h initial photoperiods, transplanted when two–three, five–six, or eight–nine nodes developed and placed under 8-, 12-, or 16-h final photoperiods. Greatest flowering percentage (100%) for CB and CP occurred when plants with two–three nodes were grown in the 16-h final photoperiod. The lowest flowering percentage for CB (3.3%) and CP (15.7%) resulted from plants grown in the 8-h photoperiod continuously (initial and final). CB and CP stem lengths (49.8 cm) were longest when grown in the 8-h photoperiod continuously and shortest with the 16-h initial and 8-h final photoperiods for CB (26.5 cm) and the 16-h photoperiod continuously for CP (25.4 cm). Fewest days to anthesis, 134 days for CB and 145 days for CP, resulted from the 16-h photoperiod continuously and greatest (216 days) from the 8-h photoperiod continuously. LH plants had a high flowering percentage (99.6%) regardless of photoperiod or transplant stage. Stem lengths were longest (60.1 cm) for LH plants exposed to the 16-h photoperiod continuously and shortest (46.2 cm) when exposed to the 8-h photoperiod continuously. LH exhibited a curvilinear response for days to anthesis with the 16-h final photoperiod producing the shortest crop time (166 days) and the 12-h final photoperiod producing the longest crop time (182 days). The experiment was repeated in 1998/1999 with high intensity discharge (HID) lighting during the initial photoperiod which increased plant quality.

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Narcissus L. `Music Hall', N. `Tahiti', Tulipa L. `Couleur Cardinal', and T. `White Emperor' bulbs were precooled at 5 °C for 0 or 5 weeks and planted 15, 30, or 45 cm deep (from bulb base) into raised ground beds under 0%, 30%, or 60% shade. Plant growth was monitored for two consecutive years after planting. Precooling reduced the percentage of T. `White Emperor' that flowered but did not affect flowering percentage of the other cultivars. Precooling delayed anthesis in one or both years for all cultivars. The greatest percentage of bulbs flowered when planted 15 cm deep and the 45-cm planting depth reduced flowering percentage. Increasing planting depth delayed anthesis for all cultivars. Increasing shade increased stem lengths in one or both years for all cultivars, but did not influence flowering percentage. Perennialization was low for all cultivars regardless of treatment. Cultivar differences in perennialization occurred; in year 2 up to 30% of N. `Tahiti' bulbs flowered vs. 32% for `Music Hall' and up to 30% of T. `White Emperor' bulbs flowered vs. only 22% of `Couleur Cardinal'.

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In greenhouse production, most floricultural crops are cultivated in soilless substrates, which often supply limited amounts of plant-available silicon (Si). The goal of this study was to determine the effects of Si supplementation on greenhouse-produced ornamental sunflower (Helianthus annuus L. ‘Ring of Fire’). Potassium silicate (KSiO3) substrate incorporation or weekly substrate drenches, sodium silicate (NaSiO3) foliar applications, and rice husk ash substrate incorporation were used as Si supplements. Silicon content of Si-treated plants increased compared with untreated controls. Depending on the source and concentration of silicon supplied, several horticultural traits were improved as a result of Si supplementation. Thick, straight stems, increased flower and stem diameters, and increased height were observed in some of the treatments, upgrading sunflower quality compared with untreated controls. However, growth abnormalities were observed when concentrations of 100 and 200 mg·L−1 Si were supplied as KSiO3 substrate drenches. In these treatments, plants appeared stunted with deformed flowers and were delayed in flowering. Consequently, Si supplementation effects on greenhouse-produced sunflowers can vary from beneficial to detrimental depending on the applied source and concentration.

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Anemone (Anemone coronaria L.), snapdragon (Antirrhinum majus L.), larkspur [Consolida ambigua (L.) P.W. Ball & Heyw.], delphinium (Delphinium ×cultorum Voss.), sunflower (Helianthus annuus L.), lupine (Lupinus hartwegii Lindl.), stock [Matthiola incana (L.) R. Br.], and pansy (Viola ×wittrockiana Gams.) were grown in raised sandy loam ground beds in double-layered polyethylene-covered greenhouses which were either unheated (ambient) or had a 55 °F (13 °C) minimum night temperature in year 1 and 36 or 50 °F (2 or 10 °C) minimum night temperature in year 2. Results were species specific; however, the extreme low temperatures [21 °F (-6 °C)] in the unheated house limited delphinium and lupine production. The warmest greenhouses (55 and 50 °F) reduced production time for anemone, delphinium, larkspur, lupine (year 2), snapdragon (year 2),stock, and sunflower. The coolest greenhouses (unheated and 36 °F) increased stem lengths for anemone (year 2), delphinium, larkspur (year 1), lupine (year 2), snapdragon, stock, and sunflower. The coolest green-houses also yielded a profit or lower net loss for all species except delphinium, lupine, and snapdragon (year 2) for which profits were highest or net losses were lowest in the warmest greenhouses.

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Most commercial and university substrate testing laboratories' recommended floriculture nutritional values are based on the saturated media extract (SME) method. With the recent gain in popularity of pour-through nutritional monitoring, alternative recommended values are needed for nutrient analyses based on pour-through extracts. Pour-through nutritional values were compared to the SME values to develop calibration curves and recommended nutritional values. Euphorbia pulcherrima `Freedom Red' Willd. ex Klotzch. were grown for two consecutive growing seasons in 16.5 cm plastic pots with Fafard 4 P root substrate and fertigated with 200, 300, or 400 mg·L-1 N from a 13N-0.88P-10.8K fertilizer. Linear relationships existed and inverse calibration curves for pour-through and SME comparisons were developed for (r 2): EC (0.98), NO3 - (0.98), P (0.97 to 0.99), K (0.99), Ca (0.94 to 0.97), and Mg (0.91). In addition, recommended pour-through substrate value ranges were developed for comparison with SME values. The established calibration curves and pour-through substrate value ranges will allow substrate-testing laboratories to make nutritional recommendations based on pour-through extractions.

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