Zinnia is one of the most popular summer garden annuals due to its bright colors and ease of culture; however, it is also prone to many diseases most notably powdery mildew, that have limited its use as a bedding plant. In 1994, ‘Profusion Orange’ was introduced after being crowned with the prestigious All America Selections Gold Medal. ‘Profusion Cherry’ and ‘Profusion White’ quickly followed, also winning All America Selections Gold Medals. The Profusion Series is highly disease resistant and heat tolerant. As the name implies, the plants are covered with medium, semi-double, 21?2-inch flowers all summer long. Profusion has great basal branching and forms mounds of color up to 18 inches tall and 24 inches wide.
Two new colors joined the Profusion series this year, Fire and Apricot. Fire features a bright scarlet orange color that lights up the garden and is a great complement to blue and yellow flowers. Apricot features flowers with a bright apricot color and blends well with soft blue, red, orange and yellow flowers. Combining Fire, Apricot and Orange makes a wonderful warm blend of colors giving a “Santa Fe” look. Profusion is ideal for use in mixed containers, landscape plantings and hanging baskets.
Profusion plugs are best produced in a 200-cell plug tray using a well-drained, soilless media with a pH of 5.8-6.2 and an initial starter charge of 0.75 mmhos. Lightly cover the seed with coarse vermiculite and allow 4-5 days for germination. The optimum germination temperature is 75-78° F.
After emergence, reduce the temperature to 65-70° F, and place the plug trays in a bright greenhouse with good air circulation. Apply 50-100 ppm nitrogen using a well-balanced calcium nitrate-based fertilizer, maintaining an EC of 1.0 mmhos. As plants progress and true leaves appear raise the fertilizer rate to 100-150 ppm nitrogen, maintaining the EC no higher than 1.5 mmhos.
Profusion flowers more quickly under short photoperiod (less than 13 hours). In early spring small plants may flower too quickly. To delay flowering and build the plant body, especially for larger pots, extend the day length to 16 hours starting at day 21 and continuing 2-3 weeks after transplanting.
Growing on to Finish
Profusion works best in 4- or 6-inch pots, with one plant per 4-inch pot and three plants per 6-inch pot. Use a well-drained, soilless medium with a pH of 5.8-6.2 and a medium initial nutrient charge. Boron deficiency, characterized by tip abortion, crinkled leaves and leaf edge burn, results at a pH over 6.5 or if insufficient boron is supplied in the feed.
Maintain night temperatures at 62-65° F and days at 68-70° F, and keep moderate to high light levels. Maintain even moisture; do not allow plants to wilt. Feed weekly with 150-200 ppm nitrogen using a well-balanced calcium nitrate based fertilizer.
Growth regulators are generally not required, but B-Nine at 25 percent is effective. Pay close attention to Cherry, as it is more vigorous than the other colors.
Sow to transplant (in a 200-cell plug tray) takes four weeks; transplant to finished pack takes 5-6 weeks; transplant to saleable 4-inch pot takes 6-7 weeks with one plant per pot; and transplant to saleable 6-inch pot takes 7-8 weeks with three plants per pot.
Watch out for thrips and aphids, as they are common pests of zinnia.