Potted roses

Consumers are constantly looking for value in whatever they purchase. The Terrazza rose series, bred by De Ruiter’s New Roses International and available exclusively from Greenheart in the United States, offers consumers a choice of using the plants in containers for the patio or in the landscape. This series contains seven floribundas that are prolific, repeat bloomers with double flowers borne in clusters. Some flowers are fragrant. The compact plants, which finish about 18 inches tall and 12 inches wide, are well-suited for perennial programs and have a quick production cycle.

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Terrazza varieties are available from Greenheart in 32-, 72- and 98-cell rooted liners. Liners should be planted into a well-drained growing medium with a pH of 5.8-6.3 and an electrical conductivity of 0.2-0.3. Liners should be planted at the same level as the surrounding root medium. Irrigate thoroughly with a fertilizer solution of 100-120 parts per million nitrogen after liners are planted.

Plants should not be pinched until the root system is well-developed and roots have reached the sides of the container. Plants can be spaced pot-tight until pinching occurs. Pinch plants by removing 1/2-1 inch above the last cut. Additional pinches can be made to produce fuller, bushier plants.

When plants are fully rooted, feed them with 150-200 ppm nitrogen from a complete nitrogen-phosphorus-potassium fertilizer with micronutrients at every irrigation. Most of the nitrogen should be in the nitrate form. Apply supplemental iron from iron chelate either as 5-10 ppm with each irrigation or as a 30-50 ppm drench every seven to 10 days (wash foliage of afterwards). During the last two to three weeks of production, lower fertilizer rates to 125-150 ppm or leach periodically with clear water.

Plants should be produced in full sun to maximize production and maintain quality. Early-spring crops benefit from the addition of supplemental light of 350-500 footcandles for 13 hours from high-intensity-discharge lamps. Light levels below 200 footcandles can result in weak stems and flower bud abortion.

Optimum night temperature range is 58°-65°F with day temperatures of 68°F-75°F. Higher temperatures speed up growth and flowering, but may also cause weaker stem and fewer flower petals.

The rate of development can be slowed by maintaining a night temperature as low as 50°F. Relative humidity must also be lowered.

To avoid disease development, relative humidity control is very important. A relative humidity of 60-70 percent is usually low enough to suppress disease pathogens.

If growth regulators are applied, better height control is achieved prior to the visible bud stage. Bonzi sprays of 30-60 ppm can be applied when new shoots measure 1-1 1/2 inches long after the first pinch. Additional applications can be made every seven to 10 days until the first visible bud.

Plants in smaller containers are ready for sale when two flowers are open and several buds are showing color. Plants finished in larger pots should show more open flowers.

Powdery mildew, aphids and spider mites are the most common disease and insect problems.

For more: Greenheart, P.O. Box 1510, Arroyo Grande, CA 93421-1510; (800) 549-5531; fax (805) 481-7374; www.greenheartfarms.com.

Specifics

Name: Rosa hybrida Terrazza series.

Crop timing: Plants produced in 6-inch pots from one 98-cell liner per pot with one pinch finish in eight to 11 weeks. Plants grown in 1-gallon containers from one 72-cell liner per pot and 10- to 12-inch patio pots with four 98-cell liners per pot, that receive two pinches, finish in 12 to 16 weeks.

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Grower benefits: Can be grown for container and landscape sales.