Hamelia patens Jacq. (Texas firebush) is a long-day plant for flower initiation and flower development; however, flower development is more sensitive to photoperiod than is flower initiation. The critical photoperiod for flower development at 25C is between 12 and 16 hours. Flowering was delayed under low light conditions, and plant dry weight was heavier and flowering time was earlier for plants grown at a constant 25 or 30C than at 20C. A greenhouse environment with a 16-hour photoperiod and moderately high temperature (25C) would be appropriate for production of H. patens.
The New Crop Program at the Univ. of Georgia has introduced about a dozen crops new to the floriculture and ornamental plant industry. None of the selections arose from controlled crosses or traditional plant breeding, but were due to discovery, natural plant mutation, and plant donations from interested individuals. All successful introductions benefitted from feedback from the industry, evaluation, research, and promotion of the taxa. No marketing was done by the university. Less than 10% of plants trialed were introduced to the industry, and not all introductions were equally satisfactory. The keys to new crop introduction are feedback from the industry, an industry willing to experiment with new material and to be as highly selective as possible in choosing the crops to be introduced. The disadvantages and benefits of establishing a New Crop Program will be discussed.
Plants were subjected to daily temperatures of 15, 20 or 25 °C after transplanting to 10cm containers. As temperatures decreased, plants were significantly slower to reach anthesis, however, however no significant differences in visible bud time occurred between 20–25 °C. Night break incandescent lighting or HID lamps for 2 or 4 weeks were used to illuminate plants during the daylight production cycle (0800–1700 hr). No differences in growth or flowering time between HID durations occurred, but both HID treatments resulted in larger plants and one week faster flowering compared with control and incandescent-lit plants. The effect of incandescent light, however, had no effect on flowering time but resulted in significantly taller plants. Additional photoperiod studies were conducted using continuous LD (night-break lighting), continuous SD (black cloth from 1700-0800) and a combination of LD-SD and SD-LD treatments. In all treatments, photoperiod had no significant effect on flowering time or growth, suggesting Ruellia `Rajin Cajin' is a day neutral taxon. Experiments with `Rajin Cajin' suggested in was a 6 week crop from plug to market.
A teaching methodology was employed to use gardeners in the community to help in the teaching of a Herbaceous Perennial Plant Identification class (8 weeks, about 160 taxa). Most universities do not have a diverse collection of herbaceous perennials planted on campus, nor do most campuses have horticultural or botanical gardens for students. Teaching plant materials with photos alone or trying to force materials in the greenhouse is not only a horticultural challenge but seldom provides students with the important identification characteristics (habit, fragrance, fruit) of the taxon. Approximately six gardeners in the community agreed to open their private gardens to the students. Plants are evaluated 2 days before class time, and a list of plants is published on WebCT each week All gardens chosen must be within 15 minutes driving time from campus. Students were able to drive to the gardens, meet the gardeners and were exposed to the plants in garden setting. Potential problems of being unable to drive to gardens, or not being able to return to the gardens to study were not realized. Gardeners embraced the program and students were enriched by studying plants in a natural garden environment. The final examination is conducted in one of the gardens visited by the class. The use of gardeners in the community has been an important part of the class for 10 years.
Minimizing environmental stress in bedding plant and greenhouse and seedling development has occupied many researchers in academia and industry for many years. The dependence on single plant germination units (plugs) for bedding plant production and high value hybrid seed demand high rates of germination and successful seedling establishment. Pre-germinating or priming of seed is an important method of germination enhancement and methods and benefits of “priming” will be discussed. Environmental options to enhance seed germination of non-primed seed include control of vapor pressure deficit (VPD) and temperature.
Enhancement of seedling establishment through growth room and greenhouse technology includes the optimal use of CO2, temperature and light. Carbon dioxide fertilization on seedlings is receiving serious study and will be further elucidated.
The influence of photoperiod, supplemental lighting, and pinching method on the growth and flowering time of Pentas lanceolata Benth. cultivated as a pot crop was determined. Pentas is a quantitative long-day plant (LDP). Plants given long days (LD) flowered 7 to 10 days earlier than those that received short days (SD). Light was supplemented during daylight hours only to distinguish from photoperiodic effect and 6 weeks of HID (640 ± 30 µmol·s–1·m–2) supplemental light also accelerated flowering. Height was retarded with chlormequat, but daminozide and ancymidol were ineffective. No growth regulator affected flowering time. Pinching delayed flowering time but increased the number of blooms per plant. Pinching to three nodes was more beneficial and resulted in faster flowering than pinching to one node. Chemical names used: 2-chloro-N,N,N-trimethylethanaminium (chlormequat); butanedioic acid mono (2,2-dimethylhydrazide (daminozide); α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol).
Limonium × `Misty Blue' plants were treated with directed sprays of gibberellic acid (GA3) at 400 mg·liter–1 at weekly intervals. All GA3 treatments accelerated flowering and increased yield of flowering stems compared to nontreated plants. Treatment at 4 weeks after planting resulted in the greatest acceleration of flowering and increase in stem yield.
Rooted terminal cuttings and dormant 1-year-old transplants of Phlox paniculata L. `Ice Cap' and `Red Eyes' were cooled for 0, 4, 8, 12 or 16 weeks and forced under long-day photoperiod provided by incandescent lights as either a night-interruption (2200–0200 hr) or extended-day (1700–2200 hr). The influence of cooling duration, long-day lighting regime, and propagule type on forcing days to flower, flowering stem counts, and flowering stem length was evaluated in a 3 × 2 × 5 factorial experiment. Cooling accelerated flowering and increased stem yield and length. Days to flower for both cultivars decreased and flowering stems and length increased linearly as cooling increased from 0 to 16 weeks, regardless of lighting or propagule type, but cooling for 8 weeks or more was necessary to produce marketable cut flower stems. Extended-day lighting produced longer stems than night interruption, and stem counts were higher among plants grown from transplants, regardless of cooling duration, lighting regime, or cultivar. Flowering stems from rooted cuttings were generally longer than those from transplants. Cut flower stems of `Ice Cap' were longer than those of `Red Eyes', but days to flower and yields for the two cultivars were similar.
The influence of temperature, irradiance, photoperiod and growth retardants on growth and flowering of Angelonia angustifolia Angel Mist series was evaluated. When temperature was increased from 15 to 30 °C, time to visible bud and time to flower decreased in a quadratic manner but total plant height and flower stem dry weight increased linearly. As irradiance increased, time to flower, time to visible bud, and height decreased quadratically. Changes in photoperiod had no effect on growth or flowering, suggesting that A. angustifolia is a day-neutral species with regards to height and flowering time. Daminozide, ancymidol, and paclobutrazol resulted in significant reduction of plant height compared with control plants but did not influence flowering time. Chemical names used: K-cyclopropyl-K-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol); butanedioic acid mono (2,2-dimethylhydrazide) (daminozide); K-[(4-chlorophenyl)methyl]-K-(1,1-dimethyethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).