Cartwheel Gerbera Culture Guide Gerbera jamesonii

Cartwheel Strawberry Twist gerbera from Syngenta Flowers Inc. was introduced to growers in 2013 as a unique color addition to the Cartwheel series, which is known for its large, semi-double flowers. This innovative color is derived from a segregating genetic that brings various flower colors and shading to each plant. The flowers can vary from plant to plant to produce a range of colors from buttery yellows with a hint of pink to deep strawberry with a hint of yellow and everything in between. To provide retailers with a high-quality Cartwheel Strawberry Twist, follow the key production tips below.
 

Production:

• Minimum Germination Rate: 90
• Seed Product Form: Raw, coated

Flowering

• Photoperiod response: Facultative short-day plant; flower initiation is earliest under day lengths 12 hours or less, but flowering will occur regardless of day length.
• High light and short days shorten time to flower. Best growth and flowering occur under a 12 - 13 hour photoperiod. Day lengths less than 12 hours result in earlier flowering, but more compact plants. Longer day lengths delay flowering by one week or more and result in plants with larger leaves.

Plug Culture

Germination stage 1 (Approximately days 1 - 4)

• From the time a seed is sown until radicle emergence takes place; usually with the root penetrating the media and some cotyledon development.
• Tray size: 72- to 128-cell size plug tray. One seed per cell.
• Cover: Seed cover is not recommended. Seeds require light to germinate.
• Light: If using a germination chamber, providing a light source of 10 - 100 foot candles (100 - 1000 lux) for 16 hours/day will improve germination.
• Temperature: Day and night: 74°F - 76°F until radicle emergence.
• Moisture: Saturated (level 5) for days 1 - 4 or until radicle emergence.
• Relative humidity: 100% from the time seeds are sown until radicle emergence, initial root has penetrated media and cotyledons appear. Expect radicle emergence in 3 - 4 days.
• Media: pH 5.3 - 5.8. EC 0.7 - 1.0 mS/cm (saturated media extract).

Germination stage 2 (Approximately days 5 - 7)

• Light: 2,000 - 2,500 foot candles (DLI (Daily light integral): 6 - 8 mols/day.
• Temperature: Once cotyledons have unfolded, reduce temperature to 72°F - 74°F.
• Moisture: After radical emergence, alternate media between wet (level 4) and moist (level 3).
• Relative Humidity: Lower relative humidity to 40 - 50% (approximately day 5). Provide horizontal airflow to aid in the drying of media through evapotranspiration.
• Media: pH 5.3 - 5.8. EC 0.7 - 1.2 mS/cm.
• Fertilizers: 13-2-13 at 50 - 75 ppm nitrogen as needed. Keep nitrogen concentration less than 100 ppm to avoid leaf distortion on young plant tissue.

Plug bulking (Approximately days 8 - 28):

• The time necessary for the shoots to proportionally fill the plug and for the roots to develop throughout the media. Plug time will vary based on growing environment and culture.
• Light: 3,500 - 5,000 foot candles; DLI: 12 - 18 mols/day.
• Temperature: 68°F - 70°F
• Moisture: It is critical to allow adequate dry back between watering to prevent stunted and distorted growth. Alternate between moisture levels wet (level 4) and medium (level 2), allowing media to dry back between watering.
• Relative humidity: 40 - 50%.
• Media: pH 5.5 - 5.8. EC 1.0 - 1.5 mS/cm .
• Fertilizer: Alternate 13-2-13 and 17-5-17 at 75 - 125 ppm nitrogen to maintain a media EC of 1.0 - 1.5. Supply 8 - 12 ppm phosphorus, 1.5 ppm iron and 0.5 ppm boron.
• Plant growth regulators: At this stage, no chemical plant growth regulation should be needed.
• Fungicides: Preventive fungicides may be applied for Rhizoctonia, Pythium and Phytophthora.

Initiated bulking (Approximately days 29 - 48):

• Seedlings develop from juvenile to mature stage, usually determined by the number of leaves present (cultivar specific). Seedlings are receptive to initiation and flower bud development.
• Light: Provide 3,500 - 5,500 foot candles.
• Temperature: 68°F - 72°F. A temperature drop of 5°F - 10°F can be used at sunrise for two hours to reduce stem elongation.
• Moisture: Alternate between moisture levels wet (level 4) and medium (level 2), allowing plants to dry back between watering. Too much water and fertilizer will cause deformed plants with thick leaves.
• Fertilizers: Alternate between 13-2-13 and 17-5-15 at 100 - 150 ppm nitrogen to maintain a media EC of 1.2 - 1.5. Supply 8 -12 ppm phosphorus, 1.5 ppm iron and 0.5 ppm boron. If leaves develop interveinal yellowing, supplemental applications of magnesium sulfate (Epsom salts) and chelated iron can be used to green plants.
• Plant growth regulators: If needed, a foliar spray of daminozide plant growth regulator (daminozide) at 1,250 - 2,500 ppm is effective.
• Fungicides: A preventive fungicide application may be applied for Rhizoctonia, Pythium and Phytophthora.

Transplant to finish (Approximately days 49 to finish):

• Optimize plant shoot and root growth, which is usually a 1:1 ratio. Flower buds are usually present and developing.
• Container size: Works best in larger, patio-ready containers.
• Light: Provide 4,000 - 6,000 foot candles. Provide an 11 - 13 hour day length for optimum vegetative growth and flowering. Cartwheel gerbera is a facultative short day plant and will flower one week earlier under 10-hour versus 16-hour photoperiods.
• Temperature: Start at 70°F - 72°F or the first two weeks after transplant and then lower to 65°F - 68°F. A temperature drop of 5°F - 10°F at sunrise for two hours can be used to reduce stem elongation. Flowering is delayed if the average daily temperature (ADT) is less than 63°F (17°C).
• Moisture: Alternate between moisture levels wet (level 4) and medium (level 2). Allow media to approach medium (level 2) before irrigating to return to wet (level 4). Adequate dry downs are critical to prevent stunted, distorted growth.
• Relative humidity: 40 - 50%
• Media: pH 5.5 - 5.8. EC 1.5 - 2.0 mS/cm. Iron deficiency can occur if pH levels rise above 6.0.
• Fertilizer: Constant feeding with a 15-5-15 or 17-5-17 at 150 - 200 ppm nitrogen to maintain a media EC of 1.75 - 2.5. Under high light conditions, 20-10-20 fertilizer can be used. Supply 8 - 12 ppm phosphorus and 1.5 ppm iron. Leaf tip yellowing or interveinal chlorosis can indicate iron deficiency. Additional chelated iron can be applied at 2 - 4 oz./100 gal to correct an iron-deficiency and to green plants. If magnesium levels are low, a one-time drench with magnesium sulfate (Epsom salts) at 8 oz./100 gal can be applied.
• Plant growth regulators: If required, an application of daminozide 2,500 - 5,000 ppm or ancymidol at 1 - 3 ppm are effective for growth control and toning. Plants grown under photoperiods longer than 13 hours can have larger leaves than plants grown under shorter day lengths. Therefore, higher PGR rates or additional applications may be required if finishing under long days. Paclobutrazol sprays at 2.5 - 5 ppm or drenches at 0.25 - 0.5 ppm can also be used. Avoid PGR sprays after flower buds reach a diameter of 1 cm (pea-sized) since this can cause small flowers and short flower stems. • Common Diseases: Foliar – Alternaria, Botrytis and Powdery Mildew; Soilborne – Phytophthora, Rhizoctonia and Pythium.
• Common Pests: Aphids, fungus gnats, shore flies, broad mites, cyclamen mites, spider mites, thrips, whitefly and leafminers.

For recommended plant protection products biological control agents for Gerbera, visit http://bit.ly/1gsSp7f

Scheduling

• Plug time: 128-cell trays: 5 - 6 weeks; 72-cell trays: 7 - 8 weeks when grown at an ADT of 68°F and under a DLI of 12 - 18 mols/day.
• Finish time from transplant: Timing will vary depending on plug size, finish container size and growing environment. At an ADT of 68°F and under long days with a DLI of 10 - 15 mols/day, 128-cell plugs (six weeks old) finished in 6-inch pots will take 9 - 11 weeks from transplant. See table. Finish time is 7 - 10 days shorter at an ADT of 73°F versus 68°F.
• Total crop time: For finishing in 6-inch pots grown under long days, at an ADT of 68°F and under a DLI of 10 - 15 mols/day, the total crop time is 16 - 17 weeks. Cartwheel is a facultative short-day plant and will flower one week faster under photoperiods 12 hours or less.

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