Gerbera is one of the most popular flowering plants. Some say it practically sells itself! However, if quality is not there, sales will suffer. For the highest-quality finished product, Tom Linwick, grower account manager for Syngenta Flowers/Goldsmith Seeds, says gerbera production requires more attention to detail than most crops.
In the early stages, gerberas require special attention to moisture management. In producing young plants, too much water between the second and fifth weeks results in plants that do not develop normally. Signs of overwatering are deformed leaves with a thick, leathery appearance. These deformed plants will not develop properly unless soil moisture is decreased.
Temperature: The optimal temperature is 74° to 75°F (23°C) for the first three to four days. Lower it after germination is complete to 70° to 72°F (21° to 22°C) for the next three to four days. Eventually lower the temperature to 68°F (20°C) for growing on.
Moisture: Keep them saturated (5) the first three days or until radical emergence (approximately the fourth day). If you are unable to dehumidify on day 4, decrease the starting moisture level from saturated (5) to a wet (4+). Media moisture should alternate between a saturated (5) to a moist (3) within 18 hours at radical emergence. Around the fifth day, begin alternating between a wet (4) and a moist (3) level. Keeping the newly germinated seedlings on the dry side will initiate rooting and help prevent foliar disease. When cotyledons are fully expanded, begin to alternate between a wet (4) and a medium (2) moisture level.
Humidity: Grow at 100 percent humidity for the first three to four days. Reduce it to 75 percent for the next four to five days. After one week, avoid disease problems by lowering the humidity to 40 to 60 percent. A maximum of 70 percent humidity should be maintained. Good air circulation is very important.
Light: Optimum day length during germination is 16 hours. During periods of low light, use supplemental lighting at 35 to 40 watt m2 (3500 to 4000 lux), or 400 foot-candles. Gerbera require light during germination so the seed does not need to be covered. If you use vermiculite to maintain a higher humidity, use a very light covering so the seed is still visible after watering the trays.
Media: A porous, well-drained media should be used with an EC of 1.2 to 1.5 and a pH of 5.5 to 5.8. Use a coarse peat to provide better aeration.
Plug Crop Time: In a larger plug, the crop time is approximately seven weeks from sowing if proper temperature, light and fertility guidelines are followed. The young plants are ready to be potted when they reach the four to five true leaf stage.
Fertilizer: Begin feeding with a complete fertilizer after the first week or once the seedlings are established. Some fertilizers that work well are a 14-4-14 or a 17-5-17 at 50 ppm or even a 20-10-20 at 60 ppm if the light levels are higher. Make sure the plants receive enough feed and the pH remains between 5.5 and 5.8. After 14 days, increase the fertilizer level to 75 ppm.
Transplant on time so plants don’t become root bound and delay flowering, inhibit development and result in plants that don’t size up properly. Make sure they aren’t planted too deeply. If the soil covers the crown of the plant, it will inhibit proper growth.
Use a fully fertilized, porous, well-drained soil. EC should be 1.5-2.0 with a pH of 5.5-5.8. A coarse peat with 20 percent perlite provides good aeration.
Start at 70-72°F for two weeks and then lower to 65-68°F. Use a 5-10 degree negative DIF or drop in temperature two hours before sunrise until 9 a.m. You can also lower the temperature at sunset for the same result.
Alternate between moisture levels of wet and medium. Allow media to approach medium before resaturating to wet. Do not allow plants to wilt, which can cause root injury.
Supplemental lighting is beneficial during winter months. In the finishing stages, avoid a daylength greater than 16 hours. When plants are getting established after transplanting, a 14-hour daylength works well, and then after seven to 10 days, reduce it to 11-13 hours. The light intensity with supplemental lighting should be 400-600 footcandles (4,000-6,000 lux); 14-22 moles.
Constant feeding with a 17-5-17 fertilizer at 150-200 ppm is needed to maintain an EC in the soil of 1.75 to 2.0. Under high light conditions, a 20-10-20 fertilizer can be used. Supply 8-12 ppm phosphorous and 1.5 ppm iron. The use of a calcium-based fertilizer is recommended during the winter months but may need to be supplemented with an ammonium-type fertilizer.
Watch your pH closely. The optimal pH is between 5.5-5.8. Gerberas favor a lower pH and will show signs of iron and manganese deficiencies when the pH reaches 6.5. At this point, the leaves will have a mottle to the foliage.
For smaller containers like 4-inch pots, apply B-Nine (daminozide) at 2,500 ppm seven to 10 days after potting. Do not apply B-Nine once buds are visible, because this will cause shortened flower stems. When pea-sized buds are visible, the plants will flower in approximately three weeks.
Preventive fungicides may be applied for Rhizoctonia, Pythium and Phytophthora.