Most people think of indoor flowering pot plants when they hear Primula. But Sakata Seed’s Primula polyanthus F1 SuperNova series is versatile for a wide range of uses including indoor and patio containers, landscape plantings and mixed combinations. There are 11 varieties and a Mix.
This early-flowering series has a consistent flowering window across all colors. Plants are compact (8 inches tall with a 5- to 6-inch spread) producing 4- to 5-inch flower umbels bearing 2-inch-wide blooms. The SuperNovas can be used as an alternative crop for early-spring or fall sales.
Plants are hardy to USDA Hardiness Zone 5. Outdoors, plants do best in cool summer conditions with adequate shade and moisture. In cold climates, plants produced from seed sown in mid-November flower in mid-March (140 days). In warm climates, plants produced from seed sown in mid-June flower in mid-November (168 days).
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Sow seed in a well-drained growing medium with a pH of 5.5 and electrical conductivity of 1.0-1.2 mmhos (2:1 slurry). Primula is sensitive to soluble salts.
Sow seed into open flats or plug trays. Cover the seed lightly with vermiculite. Light is necessary for germination and a lighted germination chamber provides the best results. Optimum germination temperature is 64°F. Germination occurs in six to seven days.
After germination, maintain 68°F with a day length of 14 hours to keep plants actively growing. If light levels fall below 200 footcandles, use supplemental lighting of 230-250 footcandles. Application of 200 parts per million nitrogen a week before transplanting will assist plants in transitioning from plug tray to final container.
Plugs are ready to transplant in six to seven weeks. Transplant plugs into a peat-based growing medium with a pH of 5.5-6. A growing temperature of 59°F is best. The temperature should be above 46°F until plants are established. Established plants grow and flower best at 43°F-50°F.
Plants are receptive to flower initiation when they’ve developed six to 10 leaves and have a well-established root system. Lower the temperature to 45°F for five to six weeks.
Once flower initiation occurs, the temperature can be raised to 59°F. Once buds appear, plants tolerate 52°F-57°F. Shading is required when plants are grown at higher temperatures. Do not allow the medium to dry out.
Use a well-balanced fertilizer to provide continuous feed of 100-150 ppm nitrogen. Discontinue using ammonium-containing fertilizers during winter and apply a calcium nitrate-based fertilizer instead. Maintain a medium pH of 6.0-6.2 to avoid iron and manganese deficiencies, which can result in chlorotic plants.
Light levels should range from 1,700-2,000 footcandles with a maximum of 3,000 footcandles. If plants are grown outdoors, plants should be shaded the first two weeks after transplanting to avoid burn.
Fungus gnats and shore flies are common during germination and plug production. Aphids, thrips, whitefly and cut worms can be insects of concern. Good airflow around plants helps lower humidity and reduce disease development, particularly Botrytis.
For more: Sakata Seed America Inc., (408) 778-7758; fax (408) 778-7768; www.sakata.com.
Specifics
Name: Primula polyanthus
Crop timing: Four-inch pots produced from seed sown in mid-November flower in mid-March. Plants produced from seed sown in mid-June flower in mid-November. Plants require a vernalization period of five to six weeks of 45°F nights for flower initiation to occur.
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Grower benefits: Low-temperature crop. Multiple uses for landscape plantings, specimen plants and combination containers. Can be used as alternative crop for early-spring or fall sales.