June 2004

Dianthus By Paul Pilon

Dianthus 'Eastern Star' bears numerous red-flowers with raisin-red centers above glaucous blue-green foliage. The flowers measure 1-inch across and have a velvety appearance, highlighted by subtle soft pink margins. It forms small compact mounds measuring about 7 inches tall x 7 inches wide and remains evergreen throughout the year. This award-winning cultivar is widely used in perennial borders throughout USDA Hardiness Zones 4-10. Eastern Star blooms prolifically in early summer and will continue to bloom sporadically throughout the season. Deadheading is highly recommended to promote a reflush of flowers.

Dianthus was named by the famous botanist Theophrastus, from the Greek words dios, meaning divine, and anthos, which translates into flower. The common name most often used for this genus is pinks, referring to the ragged edges of the flowers, which most often appear to have been cut by pinking shears. The genus dianthus contains more than 300 species, many of which are very suitable for commercial production as bedding plants, biennials and perennials.

The Chicago-based. non-profit organization, National Garden Bureau has selected 2004 as "the year of the dianthus." Perennial growers have promoted "the year of the dianthus" by producing and offering this stunning cultivar and the other cultivars of the Star series ('Artic Star', 'Brilliant Star', 'Pixie Star' and 'Spangled Star'). The Star series was bred by John Whetmon, of Whetmon & Sons from Devon, United Kingdom, and is brought to the U.S. market by Plant Haven.

Propagation

Eastern Star is most commonly propagated by vegetative cuttings. It is a patented cultivar, and a license is required to commercially propagate this variety of dianthus. Licensed propagators generally root a finished cutting in 4-6 weeks in a growing medium with both good aeration and water-holding capacities. Maintaining a soil temperature of 68-73¡ F by providing bottom heat will enhance root development. To accelerate rooting and improve uniformity, dip the base of the cuttings in a solution containing 1,000 ppm IBA rooting hormone. Plugs acquired from growers range in size from a 128-cell up to 3-inch liners.

Production

Eastern Star performs best when produced in a growing medium with both good water-holding capacity and drainage characteristics. When planting, be careful to not plant the plugs too deeply, as this could lead to crown rot. I recommend applying a fungicide drench such as Subdue Maxx or OHP 6672 (Cleary's 3336 and FungoFlo contain the same active ingredient as OHP 6672), or drench a combination of ç these two fungicides immediately after transplanting.

Eastern Star is a moderate feeder and grows well under constant liquid fertilizer programs with fertilizer rates of 50-100 ppm nitrate. Growers using controlled-release fertilizers get the best results by incorporating at a rate equivalent to 1 lb. of nitrogen per yard of growing medium or by topdressing at the medium recommended rates. For example, if your time-release fertilizer formulation is 15-9-12, meaning it contains 15 percent nitrogen; you would need to incorporate 7 lbs. of this product per yard of media to obtain 1 lb. of elemental nitrogen (one lb. is 15 percent of 7 lbs.). The pH of the growing medium should be maintained at 6.0-6.5. Water thoroughly as needed, allowing the soil to dry slightly between waterings.

The best quality is achieved when plants are grown in full sun or in greenhouses with high light intensities, preferably 5,000-9,000 foot-candles. When produced under lower light levels, the stems will become leggy, and overall plant quality will be reduced. Due to its naturally small growth habit, controlling plant height with chemical growth regulators should not be necessary.

For container production, Eastern Star is suitable for production in 4-inch to 1-gal. containers. For 1-gal. production, I have found it highly beneficial, if not necessary, to pot them in late summer or early fall for the following spring sales. This allows them to bulk up and receive vernalization, which produces larger, fuller appearing plants with numerous blooms that will be of the highest quality for spring sales. Planting in late winter or early spring produces plants that are often too small or only flower sporadically — both reduce the overall quality and salability of this crop.

For plant establishment, it is recommended to maintain average temperatures of at least 65¡ F. Once they are established, grow dianthus with 55-70¡ F day temperatures and night temperatures of 55-60¡ F. At these temperatures a quart-sized pot can be finished from a 72-cell plug in 4-6 weeks.

Dianthus is considered a day-neutral plant. Therefore, it does not have a critical photoperiod necessary to achieve flowering. Regardless of the photoperiod, Eastern Star will flower faster when grown under higher light intensities and/or long-day conditions. Providing supplemental lighting is not necessary but will reduce the time to flower, especially when grown under low light levels. Although vernalization or exposure to cold is not necessary for flowering, I would recommend providing a cold treatment to reduce both the time to flower and increase the overall number of flowers produced. After the vernalization period or spring transplanting, it generally takes 7-8 weeks to flower when grown at temperatures averaging 65¼ F. It may take 2-3 weeks longer when grown under short-day conditions.

Pests & Diseases

The primary insect observed feeding on dianthus are aphids. Although dianthus is an acceptable food source for aphids, it does not seem to be their main preference. With the presence of aphids only occurring occasionally, growers do not have to implement preventative programs but can detect their presence through weekly scouting activities to determine if control measures are necessary.

Availability

Eastern Star liners are available through several reputable licensed propagators throughout the country including Clifford Perennials and Vines; Emerald Coast Growers; James Greenhouses; Pacific Plug & Liner; Sawyer Nursery, Inc.; Skagit Gardens, Inc.; Walters Gardens, Inc.; and Yoder Brothers, Inc. Finished containers can also be purchased from many reputable growers throughout the country.