Few pot plants rival the beauty of a well grown Regal geranium. Pre-budded Regals can be flowered year-round; however, temperature, light level, and photoperiod are critical to producing high quality plants. It is also important to unpack your Regal cuttings immediately upon arrival and place under lights if required at that time of year.
Crop Timing:
Depends on cultivar, forcing environment, and whether or not plants are pinched. Non-pinched plants should flower in eight to 12 weeks, while pinched plants can take an additional three to six weeks.
Day Length:
Control is critical for Regals from September 15, through April 1; 18 hours of continuous light must be supplied during that time until flower buds show color. Additional lighting to supply the minimum of 10 foot candles at plant level can be supplied by stringing a line of 100 W incandescent bulbs at four foot centers, six feet above benches. This will supply sufficient light for two four-foot benches with an 18" inch aisle between them.
Supplemental lighting during periods of low natural light can help maintain finished plant flower quality. Natural daylight for maximum plant quality should not exceed 4,000 foot candles.
Growing Media:
Use a light well-drained, porous potting media. pH should measure 5.8 to 6.2. Many commercial soilless mixes can be used successfully, as can a media high inorganic material (i.e. 1:1:1 soil:peat:perlite). Mixes with vermiculite should be avoided due to their tendency to compact.
Planting:
Pot in 4", 5", or 6" azalea pots depending on the variety and program desired. When potting, plants should be set slightly deeper than the original soil level. Plant spacing is based on pot size, for 6" pots, set plants at one plant per square foot, while 4" pots can be spaced at 2 ´ plants per square foot.
Watering:
Irrigate three times, one hour apart, the day of potting. Over the next three days, irrigate once daily. Subsequent irrigation frequency should be determined by weather conditions and growth stage. Regals are very sensitive to drying, and the soil must be kept uniformly moist, but not wet, during the remainder of the growing cycle.
Nutrition:
Generally, fertilization should consist of constant liquid feeding at 150-175, but this may need to be adjusted depending on cultivar, environment and growing location. To provide 150 ppm N, mix 9 oz. calcium nitrate and 4´ oz. potassium nitrate in 100 gallons of water. Phosphorous and magnesium should be incorporated into the pre-plant mix to provide the correct nutritional balance. Alternatively, Osmocote can be used at ´ teaspoon per 6" pot at planting, then apply again four weeks later. Regularly conduct soil and foliar tests to determine changes in your fertilization type and schedule.
Flowering Temperature:
Maximum daytime temperature is 68° F and nighttime temperatures should not exceed 58° F. Substantially cooler temperatures will increase crop time, while higher temperatures can cause plants to stretch and result in reduced bud set or bud abortion. Proper ventilation is necessary throughout the growing cycle and is especially critical as the plants begin to flower.
Growth Regulators:
There aren't any growth regulators labeled specifically for use on Regal geraniums. Unpublished research has shown effective height control can be achieved by applying Cycocel at a rate of 3,000 ppm active ingredient (1:40 dilution), 17 days after potting. Apply at a rate to wet foliage (glisten)