Commercial Greenhouse Production
Scientific Name: Gerbera jamesonii Bolus ex Hook. f.
Common Names: Transvaal or Barberton Daisy
Dr. J. Raymond Kessler, Jr.
Gerbera Daisies are useful as cut flowers, pot crops, and as bedding plants. They may be planted in outdoor borders, in dish gardens, patio pots, or for holiday and seasonal gifts. The 3½- to 5-inch blooms come in colors ranging from red, to orange, to yellow, to pink.
Robert Jameson, a Scotsman, first discovered Gerbera Daisies while operating a gold mine near Barberton in the Transvaal area of South Africa in 1880. He donated the plant to the Durban Botanical Gardens where, the curator of the gardens, John Medley Wood, sent specimens to Harry Bolus in Cape Town South Africa for identification. Bolus then sent specimens to the Royal Botanical Gardens at Kew in England with the suggested scientific name Gerbera jamesonii. Beginning about 1890 in England, Richard Irwin Lynch carried out breeding programs that resulted in many improvements. The plant soon became popular in the Netherlands where much of the modern breeding has been accomplished.
Gerberas were not produced in North American until the early 1920s. Extensive breeding at the University of California, Davis during the 1970s lead to many plants suitable for garden use. However, breeding in Florida and Europe focused on developing long-stemmed cultivars for greenhouse cut flower production. In fact, much of the production today in Europe and Japan is for cut flowers. In the U.S., California and Florida are leading states in the production of cut flowers and tissue-cultured stock. However, the majority of cut Gerberas come from Columbia, South America, with substantial quantities coming from the Netherlands.
'Happipot' was the first seed propagated cultivar with flower stems short enough to be useful in 5- or 6-inch pots. It was introduced by Sakata Seed Company of Japan in the early 1980s. About the same time, Sunshine Research and Development selected plants for pot culture resulting in the 'Sunshine Series' and 'Sunburst Series'. These are tissue-culture cultivars are marketed through several laboratories (Plant Labs, Inc.). However, the trend today is toward seed propagated plants. Cultivar available today include the 'Small' pot Gerberas from Earl J. Small Co., the 'Nain' Series from Park Seed Company, and the 'Valley Heart' series from Valley Heart Gardens. Current breeding strives for vigorous growth, compact habit, and continuous flowering on sturdy stems.
Gerbera seed (6000 to 8000 seed per ounce) are expensive, delicate, and sensitive to germinating conditions. Considering that the crops requires 14 to 18 weeks from seed to flower, many small to medium sized grower order established plugs from specialists propagators.
Seed should come packed moisture-proof packages, and stored under cool conditions, away from strong sunlight until sown. Once the package is open, all seed should be sown at once because the seed loose their viability very quickly on exposure to room conditions. Though it is not advisable, unused seed may be re-sealed in the package and stored in a refrigerator for a short time. Recommended sowing media varies, but most consists of 40-60% peat and 40-60% perlite with a pH of 5.8-6.0 and some fertility.
Gerbera seed may be sown in open flats or in a variety of plug flat sizes. However, transplanting from open trays requires more labor and delays establishment in the new containers. The more common practice is to sow into a variety of large plug trays from 84- to 200-cells per tray. Some growers will sow into small celled trays, and then transplant up to larger trays or pots. This allows the seedlings to be sorted by size for a more uniform crop, but requires more labor. Water the sowing media before sowing, and cover the seed with a thin layer of vermiculite afterwards.
Germinate the seed using a system that maintains humidity as close to 100% as possible. Use bottom heat to maintain 70 to 75F media temperature. Some growers will place trays in plastic bags or utilize fog systems. Others use germination chambers at 73 to 75F for four to five days. Trays should receive at least 12-hours per day of incandescent light while in germinating chambers. After 7-14 days from sowing or when complete germination has occurred, remove the plastic bags and move the seedlings into the greenhouse.
Night temperatures for growing-on seedlings in the greenhouse should be 68 to 72F. At this point, protect the seedlings from full sun by providing light shade (30-40%) and a high greenhouse humidity (70-75%). During dark periods of the year, supplemental HID lighting will speed seedling growth. Apply HID lighting for at least 14-hours per day at 300 to 500 foot-candles.
Begin fertilizing the seedlings using a low ammonium fertilizer (15-5-15) when about ten days from germination. Gradually increase the fertilizer concentration up to 100 to 150 ppm nitrogen. The young foliage is sensitive to fertilizer burn so rinse the foliage with clear water immediately after fertilizing. Watch the medium pH to see that it does not rise above 6.2 or below 5.5. High pH typically results in micronutrient deficiency. Low pH can result in calcium or magnesium deficiency. Some growers transplant seedlings to large cell-packs, 2½-inch pots, or Jiffy-Strips about a month after sowing or when they have two mature leaves.
Whether the Gerbera crop is started from seed in-house or ordered from a specialists propagator, they should be transplanted to the final container six to seven weeks from seeding or when they have four to five mature leaves. An additional week may be required if the crop spends the principal amount of time in the winter. If plugs are received from a specialists propagator, remove the plugs from the shipping boxes and inspect them for insects and diseases. Then place them in the greenhouse for a day or two before transplanting to allow them to acclimate. However, transplant the plugs after two days so the plants do not become root bound. Overgrown transplants take longer to finish and are small at finish. When transplanting, plant slightly high so that the crown is not covered with soil after watering.
Potting media used for Gerberas should be loose and well-drained with a high percentage of organic matter. Many growers use 50% to 80% peat with perlite, vermiculite, calcine-clay, or course sand added for the remaining percentage. Dolomitic limestone should be added to a pH of 5.8-6.0. Superphosphate at 4.5 lbs per cubic yard and micronutrients at the manufacturer recommended rate is also added. Because Gerberas are fairly heavy feeders, a starter charge of calcium and potassium nitrate is often added to the mix at one pound each per cubic yard.
After potting, place the plants pot-to-pot where they will receive the maximum amount of light. Gerberas can be watered and fertilized overhead for about four weeks before they must be placed at final spacing.
If a starter amount of fertilizer was added to the medium, do not begin fertilizing until root reach the sides and bottom of the pot. Many sources recommend applying a low-ammonium, balanced fertilizer such as 15-16-17 (peat-lite special) or 15-15-18 at 150 to 200 ppm nitrogen on a constant liquid basis. Excellent results have been obtained using slow-release fertilizer such as Osmocote 14-14-14 in combination with the lower CLF rate.
Many of the fertility problems encountered withe Gerberas are pH related. Monitor the medium pH weekly to see that it does not rise above 6.2 or below 5.5. High pH typically results in micronutrient deficiency, frequently iron. A spray application of iron chelate at the manufacturers recommended rate will help alleviate the chlorosis symptoms. But steps must be taken to low the medium pH. Repeated application of a acid residue fertilizer such as 20-10-20 helps. Low pH can result in calcium or magnesium deficiency. Repeated application of a basic residue fertilizer such as calcium nitrate helps. Magnesium deficiency can be alleviated using 1½ pounds magnesium sulfate (Epsom salts) per 100 gallons.
A night temperature of 68F is preferable until plants establish a root system, usually during the pot-to-pot stage. Then temperatures may be reduced to 65F night temperature. Ventilation can begin during the day at 75F. Slightly warmer or cooler temperatures can be used to speed or slow the crop, but extremely higher or lower temperatures will delay finish. Elongation of the flower stalk is sensitive to positive or negative DIF either applied generally or as an early morning application.
Botrytis can be a serious problem with Gerberas during dark, cool periods in winter when the greenhouse humidity is high. Take steps to keep the humidity below 70% during the day, and below 85% at night. Good internal air circulation at night and ventilation in the daytime is essential. High humidity appears to contribute to flower stalk stretching.
Gerberas require high light intensities for good quality plants and a high flower bud count. For this reason, they are mostly produced in the spring and summer with the greater amount of production for the spring market. Gerberas appear to respond only slightly to photoperiod. Short days tend to speed flower production while long days delays flowering. Though many growers produce Gerberas with no photoperiod control. Some growers extend the photoperiod from October through March for four weeks only to get more vegetative growth before flowering. Extending the photoperiod for longer than four weeks can result in excessive foliage growth. During the seedling and pot-to-pot stage in winter, supplemental lights (HID) may be applied for at least 14 hours per day.
Gerberas should receive a thorough watering, and then be allowed to dry somewhat. This limits the growth of the flower step and discourages soil-born diseases. They should never be allowed to wilt, however. It is also a good practice to water early in the day so that the foliage is completely dry before evening.
After four weeks pot-to-pot, space the plants so that plenty of light reaches the crown and there is free air movement. Tight spacing can delay flowering and cause leaves to stretch. Exact spacing is difficult because of different pot sizes and cultivar sizes. However, begin with: 6" × 6" minimum for 4- to 4½-inch pots, 8" × 8" minimum for 5-inch pots, and 10" × 10" minimum for 6-inch pots.
B-Nine is the growth retardant of choice for Gerbera growers. Generally, the first application is made 10 to 14 days after potting to the final container at 2500 ppm. B-Nine at 1000 to 1500 ppm may also be applied in the plug stage when seedling have four to five mature leaves. The number of applications depends on the season, cultivar, and pot size. Do not apply B-nine in the last four weeks before flowers open of flower size and shape may be adversely affected.
Leaf miners, spider mites, cyclamen mites, whiteflies, aphids, and thrips are the main insect pests of Gerberas.
Powdery milder, Phytophthora, Botrytis, and Impatiens Necrotic Spot Virus are the main disease problems of Gerberas.