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- Author or Editor: James E. Faust x
Our objective was to determine the effect of planting date and pinching on flowering dates and plant size of field-grown garden mums. Experiments were conducted in the field during two consecutive growing seasons in 1997 and 1998. In one experiment, 15 to 20 cultivars were planted on five dates (14 May, 4 June, 25 June, 16 July, and 4 Aug.) and received no pinching, one manual pinch 2 weeks after potting, or two manual pinches 2 and 4 weeks after potting. In another experiment, four cultivars were planted at the five dates. Pinch treatments were control, one manual pinch, two manual pinches, one Florel spray at 500 mg·L–1, or two Florel sprays at the same time as the manual pinches but on separate plants. Data were collected for days to first color, first open flower, 10 open flowers, and full bloom. Height and width were measured at 10 open blooms. Although the 1998 season was warmer and caused heat delay, the flowering data followed the same trends as the 1997 experiments. Pinching delayed flowering for the early plant dates. Pinching did not affect plant height or plant width. Planting date affected days to 10 blooms for most early season varieties but not late-season varieties. Planting early produced larger plants and more uneven flowering and resulted in greater heat delay of heat-sensitive varieties. Florel delayed flowering and increased plant size. We concluded that pinching was not required to produce high-quality garden mums of many new cultivars.
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.
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.
Stock plants of six herbaceous species (Antirrhinum ×hybrida `Primrose with Vein' L., Chrysocephalum apiculatum `Golden Buttons', Diascia ×hybrida `Sunchimes Coral' Link & Otto, Lavendula dentata `Serenity' L., Osteospermum ×hybrida `Zulu' L., and Verbena ×hybrida `Lanai Bright Pink' L.) received nine different pinch treatments. Stock plants received a first pinch treatment at one of three pinch heights [low (L1), middle (M1), and high (H1)] followed by a second pinch at one of three pinch heights [low (L2), middle (M2), and high (H2)] in a 3 × 3 factorial arrangement. After the two pinches, cuttings were removed weekly from the stock plants. Cutting yield per stock plant increased as pinch height increased from L to H for both the first and second pinch for all species. A low first pinch followed by a low second pinch (L1L2) produced stock plants with the lowest cutting yield, while a high first pinch followed by a high second pinch (H1H2) produced the stock plants with the highest cutting yield for all species, e.g., the percentage increase in cutting yield was 133% for Antirrhinum, 98% for Chrysocephalum, 144% for Diascia, 80% for Lavendula, 250% for Osteospermum, and 44% for Verbena. This study suggests that pinch height during scaffold development of the stock plant is an important tool for increasing cutting production.
Poinsettia `Prestige', New Guinea impatiens `Sonic White', and petunia `Improved Charlie' cuttings were harvested from stock plants, weighed, placed in glass jars, and placed at 10, 15, 20, or 25 °C. Carbon dioxide accumulation was measured and used to determine respiration rates at 2, 6, 10, 24, and 48 hours. Vegetative cuttings have very high initial respiration rates that quickly decline over time. At 2 hours, respiration rates at 25 °C were 5.4-, 2.4-, and 4.3-fold higher vs. 10 °C in poinsettia, New Guinea impatiens, and petunia, respectively. By 48 hours, there was little difference in respiration rates. In a second experiment, poinsettia `Prestige' cuttings were pre-cooled at 10 °C for 0, 3, 6, 12, or 24 hours before being transferred to 20 °C. Respiration rates were measured at 0, 2, 6, 10, 24, 48, and 72 hours in the 20 °C environment. Regardless of pre-cooling duration, respiration rates increased when cuttings were transferred from 10 to 20 °C. Respiration rates of cuttings pre-cooled for 3, 6, or 12 hours were not significantly different from cuttings maintained at constant 20 °C. However, after transfer, cuttings pre-cooled for 24 hours had a respiration rate significantly lower than cuttings maintained at constant 20 °C, but by 72 hours, there were no significant differences.
Dendranthema ×grandiflorm (Ramat.) Kitamura `Powerhouse' plants were pinched to five nodes and grown in growth chambers at 35C day temperature (DT) and 14,17,21,24, or 27C night temperature (NT) to determine if NT influenced lateral shoot development on plants exposed to high DT. Vegetative cuttings were removed from two successive flushes of lateral shoots and evaluated for lateral shoot development after rooting and subsequent apex removal. Lateral shoot development was determined on a third flush of shoots that developed on the stock plants. The percentage of nodes that developed lateral shoots on stock plants or vegetative cuttings was not related to NT. The percentage of first-order, second-order, and third-order axillary nodes that developed a lateral shoot on the stock plants, averaged over all NT, was 76, 65, and 12, respectively. The percentage of nodes that developed lateral shoots on the first-order and second-order cuttings was 29 and 19, respectively. We concluded that cool NT were ineffective in preventing a decrease in lateral branching on plants grown under high (35C) DT conditions.
The effects of supplemental lighting on vinca (Catharanthus roseus L.) plant temperature were quantified in greenhouses maintained at air temperatures of 15. 25, and 35C. High-pressure sodium (HPS) lamps delivering 100 μmol·m-2·s-1 PPF provided 73 W · m-2 of total radiation (400 to 50,000 nm) to lighted plants. Plant shoot-tip temperature was measured by using 40-gauge thermocouples. Relative to air temperature, plant shoot-tip temperature depended on the irradiance and vapor-pressure deficit (VPD). Irrespective of VPD, the additional irradiance absorbed by plants under the HPS lamps increased plant temperature 1 to 2°C. Under relatively low VPD conditions (1 kPa), plant temperature was greater than air temperature, while under high VPD conditions (4 to 5 kPa), temperature of both lighted and unlighted plants remained below air temperature throughout the day. Temperature of lighted plants however, remained 1 to 2°C above that of unlighted plants. Analysis of a degree-day model of vinca development showed hastened development associated with supplemental lighting could be explained by increased plant temperature rather than any specific photosynthetic effect.
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.
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.
An energy-balance model is described that predicts vinca (Catharanthus roseus L.) shoot-tip temperature using four environmental measurements: solar radiation and dry bulb, wet bulb, and glazing material temperature. The time and magnitude of the differences between shoot-tip and air temperature were determined in greenhouses maintained at air temperatures of 15, 20, 25, 30, or 35 °C. At night, shoot-tip temperature was always below air temperature. Shoot-tip temperature decreased from 0.5 to 5 °C below air temperature as greenhouse glass temperature decreased from 2 to 15 °C below air temperature. During the photoperiod under low vapor-pressure deficit (VPD) and low air temperature, shoot-tip temperature increased ≈4 °C as solar radiation increased from 0 to 600 W·m-2. Under high VPD and high air temperature, shoot-tip temperature initially decreased 1 to 2 °C at sunrise, then increased later in the morning as solar radiation increased. The model predicted shoot-tip temperatures within ±1 °C of 81% of the observed 1-hour average shoot-tip temperatures. The model was used to simulate shoot-tip temperatures under different VPD, solar radiation, and air temperatures. Since the rate of leaf and flower development are influenced by the temperature of the meristematic tissues, a model of shoot-tip temperature will be a valuable tool to predict plant development in greenhouses and to control the greenhouse environment based on a plant temperature setpoint.