Producing The New New Guinea Impatiens
By Mike Fernandez
This has long been a gardening favourite, as reflected by its strong retail sales year after year.
By Mike Fernandez
October 2017 – A longtime garden favourite, New Guinea impatiens can be an easy growing option for the greenhouse producer as well, with a few simple tips and techniques. That is true of the newer sun loving varieties like Sun Harmony as well.
This series provides all of the same features that have made New Guinea impatiens so popular, with the added advantage and versatility of growing in partial shade and full sun alike. Sun Harmony varieties, for example, are well branched with a lovely mounded and compact habit. Plants are covered in large 5 cm flowers and excel in both the ground and containers.
Rooting and transplant: For rooting, choose a light, well draining peat media. Keep pH at 6.0 to 6.5, and maintain electrical conductivity (EC) at approximately 0.6 to 0.8.
Apply a preventive fungicide spray at sticking to protect from botrytis.
Maintain greenhouse temperatures at 22 to 24 C (72 to 75 F).
Keep soil moderately dry. No fertilizer in the mist is needed. Light levels should be high – 5000 foot-candles or more.
Time to transplant should be approximately four weeks for well-rooted liners.
Plant in January to March for a spring finish. From a 10 cm (4 to 6 inch) pot, plants will be ready for sale in eight to 10 weeks. Plant one plant per pot and three per pot with 25 cm (10 inch) pots or hanging baskets, and plants will be ready for spring sale in eight to 10 weeks.
Media: Select a well draining diseasefree medium. Keep pH at approximately 6.0 to 6.5, and maintain electrical conductivity (EC) at 0.6 to 0.9.
Fertilizer: For the first two weeks, keep fertilization at low levels (50 ppm nitrogen mist). At week three after transplant, begin feeding 65 to 80 ppm nitrogen in a well-balanced fertilizer. This should be about the time roots reach the sides of the pot. Avoid salt accumulation, as Sun Harmony can be sensitive to high salt levels. Proper runoff should prevent this.
Light: New Guinea impatiens prefer high light levels, a minimum of 5000 foot-candles.
PGRs and pinching: Sun Harmony may need plant growth regulators (PGRs). Both Sumagic and Bonzi are effective at low rates. If needed in weeks six to 14, drench with Bonzi at 1/10th of 1 ppm and up to 1/2 if needed.
Temperatures: Daytime temperatures should be 18 to 28 C (68 to 72 F). Maintain nighttime temperatures at 16 to 21 C (68 and 70 F). Stem elongation can result from overly high temperatures.
On the other hand, low temperatures can cause plants to be too compact. If grown cooler, add more production time to the crop.
Watering: Keep plants evenly moist, and avoid overwatering.
Pest and disease control: Maintaining moderate humidity levels and providing good air circulation should be part of any good preventive program. Preventing insect or disease activity starts with vigilant scouting and monitoring.
Watch for insects including thrips and broad mites, and scout for diseases including myrothecium and botrytis.
For more information on Sun Harmony or any of Danziger’s products, visit www.danziger.co.il.
Mike Fernandez is North American product manager for Danziger “Dan” Flower Farm. He can be reached at firstname.lastname@example.org.