CULTURE NOTES
9/1/2019

Modern Décor with Potted Hydrangeas

Joan Mazat

The collaborative team of Ball Ingenuity, Aldershot Greenhouses and the Hydrangea Breeder Association (HBA) brings a new generation of hydrangea to market. Kanmara has large, majestic blooms in unique shades and elegant foliage. The collection radiates glamour and is sure to steal the show on your customers’ shaded terrace, doorstep or balcony. The beautiful colors of this patio hydrangea guarantee an unrivaled display well into late summer or fall.

Pictured: Kanmara Blue Hydrangea

Kanmara H. macrophylla are supplied by Aldershot Greenhouses in Burlington, Ontario, as dormant 9-in. (23-cm) pots with six-plus canes. Aldershot follows the strict protocol for ideal production, performance and uniformity laid out by the HBA. In order for your greenhouse to finish top-quality patio hydrangeas, we offer the following guidelines.

To finish Kanmara hydrangeas, provide a soil pH of 4.5 to 5.0 for blue varieties and a soil ph of 5.5 to 6.0 for pink varieties, with light levels at 3,000 f.c. maximum, preferably below once temperatures increase in the spring. No pinching, as hydrangeas develop their flower buds during the previous autumn and are already present in the cane tips upon arrival to the grower’s door.

Different factors can contribute to the bloom time and temperature can be used to increase or decrease the rate of growth. Ideally, your average day and night temperature should be 66F (19C). Be sure to chart growth for the entire crop cycle and make changes only at one to two degrees at a time. If too rapid growth, decrease temperature. If too slow, increase temperature. As days lengthen and light quality improves, bloom time will be faster. Be sure to apply whitewash to greenhouses in the spring to 40% to 45% once wilting is observed on sunny days. Up to 75% shade may be needed in the later spring.

Be sure to space two weeks after forcing begins to prevent stretching, uneven bloom set and Botrytis. For a size of a plant like Kanmara, doing this on time is very important.

Moisture
As “hydrangea” is derived from the Greek words for water (hydro) and for vessel (angeion), keep in mind that frequent watering is needed as they develop their size using drip or sub-irrigation. Overhead watering is not recommended due to potential damage to the flower heads. When the sepals begin to color before sales, use clear water every other watering to assist in shelf life for the consumer. DO NOT ALLOW PLANTS TO WILT, particularly in the later crop stages, as this will damage the flowers and cause the leaf margins to burn.

Fertilizer
When considering fertilizing hydrangeas, different formulations are needed for pink, red and white than what’s required for blue. The suggested formulation for blue is 20-0-20 starting at the first watering at 200 to 300 ppm N. Blue varieties must have aluminum sulfate applications to bring out the blue color. The blue variety has been treated before receipt by the grower, however, this should continue for best results. (Note that aluminum and phosphorus will bind in a solution to form aluminum phosphate. Aluminum phosphate is not available to plants and will not assist in turning plants blue.)

Apply aluminum sulfate at 12g/L at hose end for blue varieties. Begin the aluminum sulfate as a soil drench and begin applications as leaves develop, repeating every seven to 10 days for a minimum of five applications. The aluminum sulfate can also lower pH, lessening the need for acidification depending on your water. Be sure to apply a fertilizer with phosphorus to the blue varieties twice during the crop time to prevent deficiencies. When doing this if using drip irrigation, be sure to flush lines with fresh water before and after application to prevent the lines from being plugged.  

Fertilizer for the pink, red and white varieties can be 20-8-20, but any well-balanced fertilizer will work starting with the first watering.

Tips for fertilizing all colors

• Maintain soil EC at 1.8 to 2.2.

• At first sign of color, fresh water can be applied.

• After first color, feeding can continue, but it’s key to lower the soil EC to 0.8 to 1.0.

• Hydrangeas love iron. Supplementing iron with iron chelate EDDHA at 1 to 3 ppm in the fertilizer mix is recommended, especially in the early weeks of forcing.

Plant growth regulators can be an excellent tool for height control and crop evenness. B-Nine is most effective, starting at a lower rate at 750 ppm and increasing to 2,500 or even up to 4,500 ppm as light intensity/temperatures increase and how much control is desired. It’s best to use early on in the crop cycle, as late applications can reduce flower size and can be applied every 10 days starting two weeks after the plants are first introduced to the greenhouse. Stop using PGRs when the flower bud petals are expanding.  

The most common pest can be spider mites and watch for powdery mildew on lower leaves. Take sound cultural practices to prevent Botrytis on the blooms.

Kanmara should be ringed due to the extreme weight of the huge flowers during time of rain. The flower heads should be supported. Total crop time is approximately 11 to 12 weeks depending on temperatures/time of year. If forced late spring into June, it can be as quick as nine to 10 weeks.

Kanmara is best placed outdoors in the deep shade in a somewhat protected area for best performance in the garden. Consider placing it where it’s too shaded for other plants to thrive due to low light. Kanmara can brighten up any covered porch, deck or entrance way! GT


Joan Mazat is Head of New Product Development for Ball Ingenuity, a division of Ball Seed that partners with breeders to bring unique and exciting plants to market. Learn more at www.ballingenuity.com. The Vander Lugt family has been growing quality flowers in Southern Ontario since 1954. Learn more about Aldershot Greenhouses Ltd. at www.agl.ca.

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