In 1998, `Freedom Red' poinsettia stock plants were grown outdoors under 0%, 60%, and 80% shade cloth. The stock plants received a single pinch leaving 10 nodes below the pinch. Cuttings were harvested once per week for 3 weeks. The cuttings were propagated, transplanted, pinched, and grown to anthesis in the same greenhouses. After anthesis, the plants were dropped onto a concrete pad from increasing heights ranging from 10 to 70 cm. Stem breakage was recorded each time the plants were dropped. Stem breakage of the finished plants increased as the percentage of shade cloth over the stock plants increased and as cutting harvest week number increased. From the Week 1 cuttings, 0%, 8%, and 10% of the lateral stems broke off of plants from the 0%, 60%, and 80% shade cloth treatments when the plants were dropped 20 cm. From Week 2 cuttings, 6%, 30%, and 36% of the lateral stems broke off the 0%, 60%, and 80% shade treatments. From Week 3 cuttings, 0%, 29%, and 43% of the lateral stems broke off of the 0%, 60%, and 80% shade treatments that were dropped 20 cm. Thirty-six percent of the Week 3 cuttings broke off of the 80% shade treatment plants before anthesis, while none of the lateral shoots broke off of the 0% shade treatment until the plants were dropped from 40 cm.
James E. Faust and Pamela Korczynski
Elizabeth Will and James E. Faust
A model was developed that will calculate the maximum number of containers that can be placed in a specified area. There are basically three patterns of container placement. First, “square” placement involves placing pots in parallel rows in both directions so that any four pots form a square. The other two methods involve staggered patterns in which any three containers form a triangle. In the “long staggered” pattern, the long rows are parallel to the long dimension of the bench or floor space, while in the “short staggered” pattern, long rows are parallel to the short dimension of the bench. Comparisons of spacing patterns were made using a range of greenhouse/bench dimensions and container sizes. In most cases, a staggered arrangement allowed a significant increase in the number of containers fitting on a bench as compared to square placement. For example, when 6-inch pots are placed pot-to-pot in an 8 × 50-foot greenhouse section or bench, “short staggered” or “long staggered” arrangement of containers permitted 10.4% to 11.9% more containers over that allowed by a square pattern. In general, the larger the bench or greenhouse section, the greater the benefit of staggered spacing. The difference between short and long staggered was usually less than 3%, and depended on the specific space dimensions. This model can be easily entered into a spreadsheet for growers to perform their own calculations.
Michael Alden and James E. Faust
The effect of night length (NL) on the flower development of poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) ‘Prestige Red’ was evaluated. Flower initiation occurred by subjecting plants to a 14-hour NL for 10 or 17 days, termed short-day (SD) treatments, and then transferring the plants to each of four NL treatments (11, 12, 13, or 14 hours) to observe the effects of NL on flower development. The plants grown continuously with the 14-h NL treatment were the control group. The timing of first color, visible bud, and anthesis were recorded during flower development, and bract and leaf data were collected at anthesis. Leaf number was unaffected by the SD or NL treatments, suggesting that flower initiation occurred during the 10-day SD treatment before the start of NL treatments; thus, the NL treatments only affected flower development. The timing of first color and visible bud were significantly delayed with the 10-day SD × 11-hour NL treatment relative to the 14-hour NL control; however, first color and visible bud were not delayed with the 17-day SD × 11-hour NL treatment. The 11-hour NL treatment resulted in fewer plants reaching anthesis, and these plants had fewer stem bracts and less bract color development compared with the 12-hour, 13-hour, and 14-hour NL treatments. Therefore, an 11-hour NL is suboptimal for flower development; nonetheless, significant development did occur. The 12-hour NL resulted in less color development than the 13-hour and 14-hour NL treatments in the lowest stem bract positions, but the plants had a commercially acceptable appearance. These results demonstrate that minimal differences in flower development occur with NL ≥12 hours, but that optimal development required NL ≥13 hours.
James E. Faust and Joanne Logan
The National Renewable Energy Laboratory developed the National Solar Radiation Database to provide accessible solar radiation data to the research community for various uses. Previously, we created a series of monthly daily light integral (DLI) maps to provide a tool for horticulturists to estimate the potential growth and flowering responses for various plants throughout the year. The original DLI maps were based on solar radiation data from 239 sites recorded from 1961 to 1990. The DLI maps presented in this article were created from an updated database that included data from 1998 to 2009. This database provides higher resolution data modeled from satellite images of cloud cover. The data are presented in pixels with each pixel representing 100 km2 of land across the lower 48 United States and Hawaii, whereas the Alaska data are 1600 km2 pixels. The database provided global horizontal irradiance data that were converted to DLI (mol·m−2·d−1) using the conversion factor of 0.007265 mol (400–700 nm)·Wh−1 (400–2700 nm), which assumes that 45% of the solar radiation is in the photosynthetically active radiation (PAR, 400–700 nm) region and 4.48 μmol·J−1 is the conversion from radiometric to quantum units. The updated DLI maps provide more geographically precise data reflecting recent weather patterns. We present a comprehensive review of recent research exploring the growth and flowering responses of horticultural crops to DLI.
Mary Vargo and James E. Faust
Herbaceous stock plant production and cutting harvest methods affect the performance of cuttings harvested from those stock plants. Specifically, the effect of daily light integral (DLI), ethephon spray applications, and the stock plant node position (NPSP) of hybrid impatiens (Impatiens ×hybrida) ‘Compact Electric Orange’ stock plants on the flowering of the harvested cuttings was examined. The DLI treatments were grouped in ranges of low (5.1–5.5 mol·m–2·d–1), medium (7.6–8.8 mol·m–2·d–1), and high (10.3–12.0 mol·m–2·d–1) levels. The stock plants were treated weekly with 0, 50, 100, 200, or 300 mg·L–1 ethephon. Cuttings were harvested from six NPSP, which refers to the location on the stock plants from which the cuttings were harvested. Time to flower of the harvested cuttings decreased as DLI increased from 5.1 to 12.0 mol·m–2·d–1, as ethephon concentrations decreased from 300 to 0 mg·L–1, and as NPSP moved from lower to upper positions within the stock plant canopy. Time to flower was highly correlated with the node position on the cutting (NPC) where the first flower appeared. For example, when flowers appeared in the lowest NPC on the shoot (NPC 1), the first flower opened 2.5 weeks after sticking the unrooted cuttings in propagation, while flowers that appeared in NPC 7, the seventh-oldest node from the base of the cutting, opened at 9.0 weeks. The results demonstrate how stock plant management practices can be manipulated to produce cuttings that allow growers to produce flowering plants on different schedules, i.e., production time can be shortened from conventional production schedules, which may allow hybrid impatiens to be marketed like bedding plant species such as impatiens (Impatiens walleriana).
Michael Alden and James E. Faust
The effects of day temperature (DT), night temperature (NT), and night length (NL) were evaluated on the flowering responses of heat-tolerant and heat-sensitive poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) cultivars Orion Red and Prestige Red, respectively. Plants were placed under 60 DT × NT × NL treatments that consisted of three DT (20, 24, 28 °C), four NT (16, 20, 24, 28 °C), and five NL (10, 11, 12, 13, 14 hours) for the first 17 days of the experiment. After 17 days, all plants were consolidated to one greenhouse with an inductive environment (14-hour NL, 24 ± 2.0 °C DT and 21.2 ± 1.4 °C NT), and the timing of first color, visible bud, and anthesis were recorded. ‘Orion Red’ reached anthesis 8 to 10 days faster than ‘Prestige Red’ across all NLs; however, in both cultivars, days to anthesis decreased in a sigmoidal pattern as NL increased. The relative rate of progress to anthesis (1/days to anthesis) under a 12-hour NL was approximately half that of plants grown at a 13- or 14-hour NL. At a 12-hour NL, the relative rate of progress to anthesis decreased linearly as DT increased for both cultivars. At 13- to 14-hour NL, DT had relatively little effect on the relative rate of progress to anthesis. Thus, high DT delayed flowering of both heat-tolerant and heat-sensitive cultivars when flower initiation occurred under NL, typical of naturally occurring NLs in September and early October (i.e., 12-hour NL), whereas high DT did not delay flowering for either cultivar under a 14-hour NL, which is typically provided under black cloth systems. In contrast, the flowering responses to NT were quite different for the two cultivars. The heat-tolerant cultivar showed relatively little change in the relative rate of progress to anthesis as NT increased from 16 to 28 °C within each NL treatment; however, the heat-sensitive cultivar displayed a large decrease in the relative rate progress to anthesis as NT increased from 20 to 28 °C within each NL treatment. Although the delayed flowering that occurred at 28 °C and 14-hour NL was significant, the relative rate of progress to anthesis at this treatment was significantly higher than the 28 °C and 12-hour NL treatment. This suggests that artificially shortening NL to 14 hours with a black cloth system does not prevent heat delay of poinsettia, but it allows for more rapid flowering than if flower initiation took place under natural NL (≈12 hours). To summarize, high DT affected flowering when flower initiation took place at 12-hour NL for heat-tolerant and heat-sensitive poinsettia cultivars, whereas high NT uniquely delayed flowering of the heat-sensitive cultivar at NL from 12 to 14 hours.
James E. Faust and Royal D. Heins
The effects of temperature and irradiance on flower initiation and development were quantified to provide a basis for an inflorescence development model. The percentage of leaf axils forming an inflorescence increased as the daily integrated PPF increased from 1 to 4 mol m-2 d-1, while the rate of inflorescence development was a linear function of temperature from 18 to 26C. The appearance of a visible flower bud in the leaf axil was correlated with leaf blade length of the subtending leaf. Mathematical functions were used to describe leaf blade length at the time of visible flower bud as a function of temperature and irradiance, and also to describe the influence of temperature on the rate of leaf extension. The time of visible flower bud in the leaf axil was then predicted by measuring the current length of the subtending leaf blade and estimating the time required for the leaf blade to extend to the length required for visible flower bud appearance. A phasic development scale was used to describe the developmental status of an inflorescence from visible flower bud to anthesis. A model was then created which predicted time to anthesis based upon temperature and the current stage of inflorescence development.
Terri Woods Starman and James E. Faust
The objective was to provide options for hanging basket production schedules by varying the number of plants per pot (one to four) and the number of manual pinches per basket (zero to two). Several species were evaluated in Spring 1995 and heat tolerance was assessed throughout the summer. Plugs (82 plugs per flat) were transplanted into 25-cm hanging baskets in a 22/18°C (venting/night temperature set points) glasshouse. Bacopa speciosa `Snowflake', Brachycome iberidifolia `Crystal Falls', Helichrysum bracteatum `Golden Beauty', Scaevola aemula `New Blue Wonder', and Streptocarpella hybrid `Concord Blue' produced quality baskets with three or more plugs per basket and no pinch. Pentas lanceolata `Starburst' and Lysimachia procumbens (Golden Globes) produced quality baskets with fewer than three plants per basket if plants received at least one pinch, however length of growing time was increased. Pentas lanceolata `Starburst', Scaevola aemula `New Blue Wonder', and Streptocarpella hybrid `Concord Blue' proved to be heat tolerant, blooming throughout the summer. Bacopa speciosa `Snowflake', Brachycome iberidifolia `Crystal Falls', and Lysimachia procumbens (Golden Globes) were not heat tolerant, i.e., ceased developing flowers in June and resumed flowering in September. Bidens ferulifolium did not produce an acceptable quality hanging basket under any experimental treatments.
James E. Faust and Royal D. Heins
Poor lateral branching sometimes occurs when certain poinsettia (Euphorbia pulcherrima) cultivars are pinched. Two experiments were conducted to determine the effect of high temperatures on axillary bud development. In Expt. 1, `Red Sails' plants were grown in a high-temperature environment (HTE) of 27°C at night (8 hr) and 30°C (3 hr), 33°C (10 hr), and 30°C (3 hr) in the day for two months, then transferred to a 20°C environment. In Expt. 2, plants grown at 20°C were transferred into the same HTE described above for 0, 2, 4, 8, 16, or 32 days and were then moved back into the 20°C environment. Axillary buds were examined for viability at the end of each experiment. In Expt. 1, only 8% of the lateral buds forming in the HTE were viable, while 80% of the buds forming in leaf axils of leaves unfolding after the plants were transferred to the 20°C environment were viable. In Expt. 2, 80% of buds produced in axils of the first four leaves to unfold after the start of the experiment were viable in all the treatments. However, the percentage of viable buds in the axils of leaf numbers 5 to 8 was 100, 100, 100, 96, 56, and 0 for the plants placed in the HTE for 0, 2, 4, 8, 16, and 32 days, respectively. These data indicate day temperatures of 30 to 33°C adversely affect lateral shoot development of `Red Sails' poinsettia.
James E. Faust, Elizabeth Will, and Millie Williams
Graduate students received training in total crop management (TCM) techniques including pest scouting and trapping, nutritional monitoring, and graphical tracking of crop height. In 1995, one student visited five greenhouse businesses biweekly during the poinsettia (Euphorbia pulcherrima Willd.) season to provide TCM training to one greenhouse employee per business. In 1996, a second student visited one greenhouse business every week during the poinsettia crop to conduct the TCM program for that business. The students benefited from the gained practical knowledge of greenhouse production techniques and TCM techniques, and they also benefited from the opportunity to visit commercial greenhouses and interact with staff throughout the production cycle for an entire crop. This program also provided the students with the opportunity to develop their teaching, communication and training skills. The participating growers benefited during this study from receiving useful production information and TCM training. An evaluation of the program conducted in 1998 indicated that four of the five participating businesses continue to use some TCM techniques, while two of the five have fully integrated the TCM program into their normal production routines.