Argyranthemums for Spring Color

Jessa Findley

Presented in a cheerful range of spring colors from canary yellows to breezy pinks, argyranthemum are the easy spring daisies that gardeners love. While newer argyranthemum are much more heat tolerant than older varieties, they’ll still do best with cool night temperatures and should be sold in early spring. New varieties have been selected to flower continuously without deadheading; however, in warmer climates, the plants may still flush out of bloom if the night temperatures are regularly staying in the high 70s or above. The plants should continue to do fine, just give them a trim using a sharp pair of scissors or pruning shears. This will help induce more branching and fresh growth, and the plants will be at their best when night temperatures drop and the plants begin to bloom again.

Growing On
Transplant liners into a well-drained medium with a pH of 5.8 to 6.2. Do not over-saturate the media during the initial rooting stages, as this will slow down root development. Begin fertilizing with a complete and balanced fertilizer that includes minor elements after plants have taken root. Drench with a broad-spectrum fungicide immediately after transplant to prevent
disease problems.

Argyranthemum grow best under cool temperatures and high light. Day temperatures of 65F to 75F (18C to 24C) and nights of 50F to 60F (10C to 15C) are ideal. Cooler temperatures can be used to control growth, but flowering will be delayed. Warmer temperatures may produce stretched growth and the need for chemical plant growth regulators. Light levels are preferably between 5,000 to 7,000 foot candles. Supplemental lighting can be used where dark, cloudy conditions persist. If the climate is favorable, growing in a retractable greenhouse or even in a field will provide the desired light levels.

At least one pinch is usually needed to promote branching one to two weeks after transplanting. Be sure to pinch with sterile instruments and avoid standing water on the cut to prevent water-borne pathogens from infecting the plant, especially Crown Gall.

Fertilize with a constant liquid feed at 200 to 250 ppm N. If soluble salts build up, leach with clear water every third irrigation. A cal-mag blend should be applied after the plants have reached a prefinished stage to avoid interveinal chlorosis caused by magnesium deficiency. A supplemental iron chelate or iron sulfate may be needed to correct iron deficiency if the media pH levels get too far above 6.0; a pH of 5.8 to 6.2 is ideal. Keep plants evenly moist, but not overly wet through the production process; plants should not be allowed to wilt.

If growth regulators are required, applications of Cycocel (1,000 to 1,500 ppm) or
B-Nine (1,500 to 2,000 ppm) can be applied two to three weeks after first pinch. Applications can be re-applied every two weeks if needed, but cool growing conditions are the preferred method of regulating growth.
Due to the cool and moist conditions of the growing period, growers should regularly scout for fungus gnats, botrytis, Phythium and Phytophthora. Stem canker and Rhizoctonia can also affect production.

Consumer care
Argyranthemum are tough and are popular with the end users for their resilience and powerful impact. They prefer full sun and fertile soil with good drainage. Regular pruning will keep the plants compact and may increase flowering, but in general, they don’t require a lot of maintenance. Most varieties should continue bearing loads of cheerful daisy blooms until the first hard freeze in autumn. GT

Pictured from left to right: Argyranthemum frutescens Molimba Helio White, Vanilla Butterfly, Molimba Pink and Butterfly.

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Jessa Findley is the pre-finished plant grower at EuroAmerican Propagators. You can reach her at jfindley@pweuro.com.