Growing:
Any good, porous soil mix will be suitable for Regal production. Regals produce a fairly fine root system, which can be sensitive to over-watering, so it is best to use a well-drained mix of high quality peat and 15% to 25% perlite. Water plants thoroughly at the start, Regal roots will not tolerate high EC's. A good soil starting range would be a pH of 5.6 to 6.0 and an EC of .75 to 1.0 mmhos. Newly planted liners will root aggressively, with new roots visible at the edge of the container from 7 to 10 days after planting. Fertilize to maintain a soil EC of .9 to 1.1 with a balanced fertilizer. Regals respond well to cal/mg type fertilizers alternated with 20-10-20 applied at 150 ppm. Light levels are essential to quality Regal production. It is important to maintain high (>4000ftc) light during winter months. This helps develop greater petalage in the flowers and fuller, more compact plants.
Lighting:
The flower development process includes extended-day lighting. This can be achieved with 'mum' lighting (100 watt bulbs on 6' centers, 4' above the crop) from 5 am until daylight and 4pm until 8pm from November 1st until April 1st. There is a strong relationship between total irradiance (amount of accumulated light) and flower quality. Essentially, the more light the plants get, the more petals in the flowers.
Insects and Diseases:
The most significant malady of Regal Geraniums is greenhouse whitefly. Regals are a favorite food and a good indicator plant for whitefly scouting. Yellow sticky cards should be used to monitor adult populations during production. Marathon®, applied during the vegetative growing stage has been an effective control. Other products such as Distance®, Orthene®/Tame® and M-Pede® are also effective. In any case, it is important to achieve control during the non-flowering phase because Regal flowers are sensitive to most chemical sprays. While not a significant problem during the growing phase of Regals, Botrytis can be damaging to a finished crop. Flowering plants should be kept in areas where good horizontal airflow is available, and water can be kept off the flowers. Additionally, preventative Botrytis sprays used prior to first color will reduce disease pressure and help ensure a problem free finish. As with all Pelargonium species, Regals can be host to Bacterial Blight (Xanthomonas c. pelargonii.) Although symptomless in Regals, Bacterial Blight can be spread from infected Regals to other Geranium species. Culture Indexing is the most effective method of assuring the integrity of a Regal crop. Carrying stock of a 'favorite' old Regal variety may also mean carrying an undetected and unwanted pathogen.
Growth Regulators:
Culture is the most effective and preferred method of growth regulation on Regals. Cool nights, high light, moderate moisture and day temperatures will easily produce outstanding quality Regals. Current experience suggests two additional tools: Cycocel® and Bonzi®. Cycocel®, used at 1500 to 3000 ppm, until bud elongation, will reduce stretch. Also, growers are reporting good success with Bonzi® at 8 ppm, used as often as weekly, until plants are showing color. Use growth regulators with caution and trial them in your growing environment before broad use is adopted.
Finishing:
The breeding and selection work done by David Lemon of Oglevee Ltd. has greatly improved the flowering speed and performance of Regals. Today's cultivars are ready to sell in 7 to 10 weeks after completion of bud initiation. This dramatic reduction in crop times makes Regals a much more predictable crop. Finishing Regals is nothing more than an extension of the budding process. Maintain 55ºF soil night temperatures and 65ºF day temperature with a relative humidity of < 70%. Light levels may go as high as 4000 f.c. until the plants begin to show color. At this time, light levels should be reduced to 2500 f.c. to reduce leaf temperature and extend flower longevity. Fertilizer levels should not exceed 1.1 mmhos, and pH of 5.6 to 6.0 will maintain adequate micro-nutrient availability. Once the flower buds have developed and begun to elongate, finished plant size can be increased by raising night temperatures to 62F. This should only be done during the last 3 to 4 weeks of production. Growing of a 4", single non-pinched plant can be done at 3 to 4 plants per square foot. A 6" single non-pinched plant would require spacing of 12", while a 6 1/2" single plant from a pinched liner, or 3 plant non-pinched should be spaced at 15" on center. Other container sizes such as 10" to 12" hanging baskets or patio pots are becoming increasingly popular as well.