Search Results

You are looking at 61 - 70 of 84 items for

  • Author or Editor: Royal D. Heins x
  • All content x
Clear All Modify Search
Free access

Paul R. Fisher, Royal D. Heins, Niels Ehler, Poul Karlsen, Michael Brogaard, and J. Heinrich Lieth

Commercial production of Easter lily (Lilium longiflorum Thunb.) requires precise temperature control to ensure that the crop flowers in time for Easter sales. The objective of this project was to develop and validate a greenhouse decision-support system (DSS) for producing Easter lily to predetermined height and flower date specifications. Existing developmental models were integrated with a knowledge-based system in a DSS to provide temperature recommendations optimized for Easter lily scheduling and height control. Climate data are automatically recorded in real time by linking the DSS to a greenhouse climate control computer. Set point recommendations from the DSS can be manually set or automatically implemented in real time. Potential benefits of the project include improved crop quality and the transfer, validation, and integration of research-based models. The DSS was implemented at several research and commercial locations during the 1994 Easter lily season. DSS recommendations were compared with the strategies of experienced growers. The system design, implementation, production results, quality of recommendations, and potential are discussed.

Free access

Genhua Niu, Royal D. Heins, Arthur C. Cameron, and William H. Carlson

Flower size generally decreases as temperature increases. The objective of this research was to investigate during development when flowers of Campanula carpatica Jacq. `Blue Clips' and `Birch Hybrid' are sensitive to temperature by conducting two temperature-transfer experiments. In the first experiment, plants were grown initially at 20 °C and then transferred at visible bud to 14, 17, 20, 23, or 26 °C until flower. In the second experiment, plants were transferred from 14 to 26 °C or from 26 to 14 °C at 1, 3, or 5 weeks (`Blue Clips') or at 1, 2, or 3 weeks (`Birch Hybrid') after flower induction. Temperature before visible bud had little effect on final flower size for both species. For example, flower diameter of `Blue Clips' was similar among plants grown at constant 14 °C or grown at 20 °C initially and then transferred at visible bud to 14 or 17 °C. Similarly, flower diameter of plants grown at constant 26 °C was similar to those grown at 20 °C initially and then transferred at visible bud to 26 °C. Flower diameter in these species is correlated with the temperature after VB in the 14 to 26 °C and decreases linearly as the temperature after VB increases.

Free access

Genhua Niu, Royal D. Heins, Arthur C. Cameron, and William H. Carlson

Campanula carpatica Jacq. `Blue Clips' plants were grown in a greenhouse under ambient (400 μmol·mol-1) and enriched (600 μmol·mol-1) CO2 concentrations, three daily light integrals (DLI; 4.2, 10.8, and 15.8 mol/m per day), and nine combinations of day and night temperatures created by moving plants every 12 h among three temperatures (15, 20, and 25 °C). Time to flower decreased as plant average daily temperature (ADT) increased. Flower diameter decreased linearly as ADT increased in the 15 to 25 °C range and was not related to the difference between day and night temperatures (DIF). Increasing DLI from 4.2 to 10.8 mol/m per day also increased flower diameter by 3 to 4 mm regardless of temperature, but no difference was observed between 10.8 and 15.8 mol/m per day. Carbon dioxide enrichment increased flower diameter by 2 to 3 mm. Number of flower buds and dry mass at high and medium DLI decreased as plant ADT increased. Plant height increased as DIF increased from ñ6 to 12 °C. Number of flower buds and dry mass were correlated closely with the ratio of DLI to daily thermal time using a base temperature of 0 °C.

Free access

Erik S. Runkle, Royal D. Heins, Arthur C. Cameron, and William H. Carlson

Intermediate-day plants (IDP) flower most rapidly and completely under intermediate photoperiods (e.g., 12 to 14 h of light), but few species have been identified and their flowering responses are not well understood. A variety of experiments was conducted to determine how light controls flowering and stem extension of Echinacea purpurea `Bravado' and `Magnus'. Both cultivars flowered most completely (79%) and rapidly and at the youngest physiological age under intermediate photoperiods of 13 to 15 h. Few (14%) plants flowered under 10- or 24-h photoperiods, indicating E. purpurea is a qualitative IDP. Plants were also induced to flower when 15-h dark periods were interrupted with as few as 7.5 min of low-intensity lighting (night interruption, NI). Flowering was progressively earlier as the NI increased to 1 h, but was delayed when the NI was extended to 4 h. Stem length increased by 230% as the photoperiod or NI duration increased, until plants received a saturating duration (at 14 h or 1 h, respectively). At macroscopic visible bud, transferring plants from long days to short days reduced stem extension by up to 30%. Flowering was inhibited when the entire photoperiod was deficient in blue or red light and was promoted in a far-red deficient environment, suggesting that phytochrome and cryptochrome control flowering of E. purpurea. Because of our results, we propose the flowering behavior of IDP such as E. purpurea is composed of two mechanisms: a dark-dependent response in which flowering is promoted by a short night, and a light-dependent response in which flowering is inhibited by a long day.

Free access

Erik S. Runkle, Royal D. Heins, Arthur C. Cameron, and William H. Carlson

Thirty herbaceous perennial species were treated at 5°C for 0 or 15 weeks. Critical photoperiods for flower initiation and development with and without a cold treatment were determined. Photoperiods were 10, 12, 13, 14, 16, or 24 hours of continuous light or 9 hours plus a 4-hour night interruption. Continuous photo-periodic treatments consisted of 9-hour natural days extended with light from incandescent lamps. Species were categorized into nine response types based on the effects of cold and photoperiod on flowering. Plants had three flowering responses to cold treatment: obligate, facultative, or none. The perennials were obligate long-day, facultative long-day, or day-neutral plants. For example, Campanula carpatica `Blue Clips' had no response to cold and was an obligate long-day plant requiring photoperiods of 16 hours or longer or night interruption for flowering. Rudbeckia fulgida `Goldsturm' had a facultative response to cold and required photoperiods of 14 hours or longer or night interruption for flowering. Veronica longifolia `Sunny Border Blue' had an obligate cold requirement and was day-neutral. Some species responded differently to photoperiod before and after cold. Leucanthemum ×superbum `Snow Cap' flowered as an obligate long-day plant without cold and as a facultative long-day plant after cold. Response categories are discussed.

Free access

Erik S. Runkle, Royal D. Heins, Arthur C. Cameron, and William H. Carlson

Twenty-four herbaceous perennial species were treated at 5C for 0 or 15 weeks. Critical photoperiods for flower initiation and development with and without a cold treatment were determined. Photoperiods were 10, 12, 14, 16, and 24 h of continuous light and 9 h plus a 4-h night interruption. Continuous photoperiodic treatments consisted of 9-h natural days extended with light from incandescent lamps. Response to cold and photoperiod varied by species; Scabiosa caucasica `Butterfly Blue' flowered without a cold treatment under all photoperiods after 8 to 10 weeks of forcing, but plant height increased from 14 to 62 cm as daylength increased. Rudbeckia fulgida `Goldsturm' flowered without cold after 13 to 15 weeks of forcing, but only under 16 hours of continuous light and night interruption treatments. Heuchera sanguinea `Bressingham Hybrids' did not flower without cold under any photoperiod but did flower under all photoperiods with cold. The only Lavendula angustifolia `Munstead Dwarf' plants that flowered without cold were those under 24-h continuous light; ≈60% flowered. After cold, some lavender plants flowered under all photoperiods, and the flowering percentage increased with increasing daylength.

Free access

Mei Yuan, William H. Carlson, Royal D. Heins, and Arthur C. Cameron

Scheduling crops to flower for specific dates requires a knowledge of the relationship between temperature and time to flower. Our objective was to determine the relationship between temperature and time to flower of four herbaceous perennials. Field-grown, bare-root Coreopsis grandiflora `Sunray', Gaillardia grandiflora `Goblin', Rudbeckia fulgida `Goldsturm', and tissue culture-propagated Chrysanthemum superbum `Snow Cap' were exposed to 5C for 10 weeks. They were grown at 15, 18, 21, 24 or 27C under 4-h night interruption lighting. Time to visible bud (VB) and first flower (FLW) were recorded. Days to VB, days to FLW, and days from VB to FLW decreased as temperature increased. Time to flower at 15C was 70, 64, 96, and 54 days and 24, 39, 48, and 36 days at 27C for Coreopsis, Gaillardia, Rudbeckia, and Chrysanthemum, respectively. The 27C temperature apparently caused devernalization on Coreopsis because only 40% of the plants flowered. The effects of temperature on flower size, flower bud number, and plant height also are presented.

Free access

Cheryl Hamaker, William H. Carlson, Royal D. Heins, and Arthur C. Cameron

To determine the most effective lighting strategies for flower induction of long-day (LD) plants, 10 species of herbaceous perennials were chilled at 5C for 0 or 12 weeks and then forced at 20C under the following photoperiods: short day, 4-h night interruption (4-h NI), 7-h night interruption (7-h NI), 7-h day extension, 7-h predawn (7-h PD), and 24-h continuous light (24-h). All treatments consisted of a 9-h photoperiod of sunlight supplemented with 90 μmol·m–2 from HPS lamps. LD treatments were delivered by incandescent lights and induced flowering in obligate LD plants. Rate of flowering, height, and bud number at first flower varied among species and LD treatments. Although flowering was accelerated under 24-h and 7-h NI for most species, it was delayed under 24 h for Coreopsis verticillata `Moonbeam' and Campanula carpatica. For unchilled plants of most species, flowering was delayed under 7-h PD compared to other LD treatments. Chilling decreased time to flower and reduced differences between LD treatments. Coreopsis `Moonbeam' and C. Ianceolata `Early Sunrise' were shorter when grown under 4-h NI.

Free access

Catherine M. Whitman, Royal D. Heins, Arthur C. Cameron, and William H. Carlson

The influence of cold treatments and photoperiod on flowering of 8- to 11-node and 18- to 23-node Lavandula angustifolia Mill. `Munstead' plants from 128-cell (10-mL cell volume; P1) and 50-cell (85-mL cell volume; P2) trays, respectively, was determined. Plants were stored at 5 °C for 0, 5, 10, or 15 weeks, then forced under a 9-h photoperiod (SD), or under a 4-h night-interruption (NI) (2200 to 0200 hr) photoperiod at 20 °C. Percentage of plants flowering, time to flower, and plant appearance were evaluated. Increasing duration of cold treatment was associated with an increase in flowering percentage in plants from both cell sizes. More plants flowered under NI than SD except in P2 cooled for 15 weeks, where all plants flowered. Average time to visible bud (VB) and to opening of the first flower (FLW) generally decreased with increasing duration of cold treatment. Inflorescence count in P2 plants increased with increasing duration of cold treatment. To determine the relationship between forcing temperature and time to flower in L. angustifolia `Munstead', three sizes of plants were exposed to 5 °C for 13 weeks and then forced under a 4-h NI (2200 to 0200 hr) at 15, 18, 21, 24, or 27 °C. Plants generally flowered more quickly at higher temperatures, time to FLW decreasing from 77, 71, and 60 days at ≈15.6 °C to 46, 40, and 36 days at ≈26 °C for P1, P2, and 5.5-cm (190-mL pot volume) (P3) plants, respectively. Generally, P1 plants flowered 5 to 10 days later than P2, and P2 flowered 5 to 10 days later than P3.

Free access

Erik S. Runkle, Royal D. Heins, Arthur C. Cameron, and William H. Carlson

Six obligate long-day species of herbaceous perennials were grown under six night-interruption treatments to determine their relative effectiveness at inducing flowering. Photoperiods were 9 hours natural days with night interruptions provided by incandescent lamps during the middle of the dark period for the following durations: 0.5, 1, 2, or 4 hours; 6 minutes on, 54 minutes off for 4 hours (10% cyclic lighting); or 6 minutes on, 24 minutes off for 4 hours (20% cyclic lighting). Response to night interruptions varied by species, but five of the six species flowered most rapidly and uniformly under 4-hour night interruption. Few or no Campanula carpatica `Blue Clips', Rudbeckia fulgida `Goldsturm', or Hibiscus ×hybrida `Disco Belle Mixed' plants flowered with 1 hour or less of continuous night-break lighting. All Coreopsis ×grandiflora `Early Sunrise' flowered, but flowering was hastened as the duration of night interruption increased. Echinacea purpurea `Bravado' flowered similarly across all treatments. In general, the effectiveness of the night-interruption treatments at inducing flowering was 4 hours > 2 hours > 20% cyclic > 1 hour > 10% cyclic > 0.5 hour.