February 2008

Calibrachoa Superbells Series By Jeanine Standard

Calibrachoa has not been a part of our industry for very long: The first plants were taxonomically described in 1989 and the first cultivars released in 1992. The original plants were found in coastal areas clinging to rocks and surviving in some pretty harsh conditions, and they so much resembled petunias that they were originally referred to as "Seashore Petunias." Since their release in the early '90s, this crop has grown faster than most other genera and has become a major crop in its own right.

Superbells calibrachoa is a popular genus from Proven Winners, and this year's introductions expand the already strong color palette to a total of 24 choices. Joining the lineup for 2008 are Apricot Punch, Dreamsicle, Saffron, Scarlet, Trailing White, White and Yellow Chiffon.

Scheduling

Superbells are a terrific crop for early spring through fall finish. A 4- to 5-inch container will need 4-6 weeks to finish, with 6-inch and gallon pots requiring 5-7 weeks; an 8-inch container needs 7-9 weeks; and a 10- to 12-inch container will take 10-12 weeks.

Culture

Use a porous media that will not hold an overabundance of moisture. Superbells tend to produce roots quickly and maintain a healthy root system in a peat-based media blended with bark and perlite. Keep liners moist upon transplant into the new media to maintain contact between the plant roots of the liner and the new media, but do not oversaturate. Begin allowing the media to dry between irrigations once the roots have formed. It is very important to not overwater the plants once they have established themselves. Also, do not stress the plants by allowing them to wilt heavily.

A constant application of a balanced feed at a rate of 200- to 250-ppm nitrogen that supplies 25 to 30 percent ammoniacal nitrogen will promote fast growth and lush green color. Reduce ammonium levels if you begin to see signs of stretch. Aim for a pH of 5.5-5.8 at all times and an EC of 0.6-0.9 (using a 2:1 extraction method).

Grow moderately warm at 68-70¡ F during the day and 65-68¡ F at night to establish the root system quickly. Once the plants are rooted and begin filling the container, drop to a constant temperature of 63-65¡ F to slow up the growth and harden off the plant. Superbells love the sun. High light levels promote compactness and accelerate the natural branching of this plant. Once established, Superbells do well when hardened off outdoors in the spring months and can even tolerate a mild frost +/-28¡ F.

Growth Regulation For pots 6 inches and smaller, pinch at transplant only. For hanging baskets and pots larger than 6 inches, soft pinch at planting and trim around the pot just prior to hanging. Five- to 10-ppm Sumagic (uniconazole), or a tank mix of B-Nine (daminozide) at 2,500 ppm and Cycocel (chlormequat chloride) at 500 ppm can be used by Northeastern growers to control growth. In the South and West, a higher rate of either of these chemicals may be necessary.

'Superbells Blue', 'Superbells Tequila Sunrise', 'Superbells Scarlet', 'Superbells Dreamsicle' and 'Superbells Peach' can be more upright, especially in lower light conditions. These varieties might require extra pinching and PGRs to control growth. 'Superbells Red' and 'Superbells Cherry Red' are very responsive to PGRs, so use lower rates.

Insect and Disease Control

In general, be sure to disinfect your greenhouse area prior to the introduction of new plant material to help prevent any insect or disease onset. Disinfectants such as bleach, Green-Shield and ZeroTol are all effective.

As Superbells grow on, be sure to watch for fungus gnats, thrips and aphids. Fungus gnats and aphids are the most common pests of Superbells. Be sure to check hanging baskets that are up high, as it can be easy to forget to scout for insect problems with pots high in the rafters.

Superbells have a higher level of tolerance to pythium, phytoptherea and thelaviopsis than other calibrachoa do, but it is still important to maintain proper pH and ensure proper air circulation, water management and soil porosity. Drench with a broad-spectrum fungicide once the roots have reached the edge of the pot.