Growing Tips for Summer Spice Hardy Hibiscus
The Summer Spice Hibiscus collection, with its distinct bloom colors and noteworthy compact habits, had the distinction of receiving two Medal of Excellence awards from Greenhouse Grower for Editor’s Choice and Readers’ Choice in 2018. The deeply incised foliage in dark and green hues with an abundance of blooms makes Summer Spice hibiscus a worthy plant for the garden.
“We were very impressed with the growth habit of the Summer Spice series,” says Roger McGaughey, the Senior Head Grower at Pioneer Gardens in Deerfield, MA.
This year, Pioneer Gardens produced rooted liners from unrooted cuttings supplied by J. Berry Nursery. Pioneer Gardens grows bareroot Summer Spice Hibiscus for 10-inch and 3-gallon deco containers. First blooms were spotted at the beginning of July and large 6- to 8-inch flowers continued until the first major frost.
Hibiscus plants are heavy feeders. A liquid feed application with extra minors added helps with early establishment after planting in the field or containers, says McGaughey. Then follow with a slow release fertilizer including extra minors to help produce plants with strong root and shoot systems. These hibiscus love the sun and need moist, well-drained soil. Keeping them well watered provides large flowers and lush foliage. Although Summer Spice Hibiscus are considered winter hardy perennials, McGaughey recommends Northern growers take precaution against frost in late spring to prevent foliar damage, while Southern growers should water more frequently during the growing season and expect blooms earlier than July.
Keep in mind that hibiscus is a late dormancy breaker and thrives in warmer weather, so it is one of the last perennials to emerge in spring. McGaughey says finishing growers will want to wait to plant until week 12 or later, but the vigorous growth makes up for the late start. Pinching achieves multiple breaks early on and is the best method to maintain a fuller pot. Plant growth regulators can be used to keep internodes short on young plants, says McGaughey, who adds that a mix of Dazide at 2500 ppm and Cyclocel at 750 ppm, every seven to 10 days, was used effectively.
Japanese beetles love to feast on hibiscus, along with thrips and whiteflies. Using a biological control program is an effective way to keep young plants insect free while protecting frequent pollinators, McGaughey says. He also recommends a fungicide program aimed at Botrytis and leaf spot prevention..
McGaughey’s Recommendations for Growing Summer Spice Hardy Hibiscus Successfully:
Fertilizer: Liquid feed application, 200 ppm 14-4-14, with extra minors added. Continue with a slow release fertilizer with extra minors.
Propagation: Not permitted.
Plant Growth Regulators: Not needed, pinching provides a better result.
Lighting: Start the bareroots in late spring.
Pinching: Yes, to develop more breaks early on.
Growing media: Average soil, slightly acidic
Irrigation: As needed, drip rather than overhead is ideal.
Planting/Scheduling: Hardy from Zone 4a to 9b.
Learn more about Summer Spice Hardy Hibiscus at JBerryNursery.com.