September 2009 Culture

Dianthus ‘Coconut Punch’ By Paul Pilon

With its ease of production and blooming characteristics, dianthus continues its popularity as a mainstream perennial for growers, landscapers, and gardeners alike. 'Coconut Punch' is the result of the breeding efforts of Kevin Hurd from Walters Gardens, Inc.

'Coconut Punch' produces an abundance of fragrant, intricately patterned, 11/2- to 2-inch double blooms. The flowers open deep red with white blotches in the center of each petal. As the blooms mature, the white blotches expand and the red coloration lightens, leaving a wine-colored ring around each petal. This variety is one of five cultivars in the Fruit Punch series. The other cultivars in this series are 'Apple Slice', 'Black Cherry Wild', 'Dragon Fruit' and 'Pomegranate Kiss', which have all been selected for both their heat and humidity tolerance and colorful double blossoms.

'Coconut Punch' blooms prolifically in the early summer and continues to bloom sporadically throughout the season. Deadheading is recommended to improve plant appearance during the summer and promote a reflush of flowers. The bicolored double flowers are held above compact mounds of glaucus blueÐgreen foliage measuring 12 inches wide and tall when in bloom. It performs well throughout USDA Hardiness Zones 4-9 and AHS Heat Zones 8-1. In the landscape, dianthus prefers full sun, but partial sun is acceptable.

'Coconut Punch' is an ideal perennial for container, border or mass plantings. Once established, dianthus is fairly drought tolerant. The foliage is deer resistant, and the flowers attract butterflies and can also be used in cut or dried flower arrangements. With these attributes and flower power, this fragrant and colorful variety will add some real "punch" to your perennial program.

Propagation

Dianthus 'Coconut Punch' is vegetatively propagated by tip cuttings and is available exclusively from Walters Gardens, Inc. Because a plant patent is being sought (PPAF), unlicensed propagation of this cultivar is prohibited.

Production

'Coconut Punch' performs best when grown in a moist, well-drained medium with a slightly acidic to neutral pH: 6.0-6.5. Many commercially available peat- or bark-based growing mixes work well provided there is adequate drainage. Growers commonly produce dianthus in quart to gallon containers. When planting, the liners should be planted so the original soil line of the plug is even with the surface of the growing medium of the new container. Planting the crown too deeply will lead to crop variability and losses from crown rots. It is often beneficial to apply a broad-spectrum fungicide such as Banrot or Hurricane after planting.

Grown in containers, dianthus require average irrigation and do not tolerate overly wet or overly dry conditions or extreme wet-dry cycles. Under consistently wet conditions, they are susceptible to crown and root rots. When irrigation is necessary, water plants thoroughly and then allow the soil to dry slightly between irrigations.

Dianthus are light to moderate feeders; nutrients can be delivered using water soluble or controlled release fertilizers. Growers using water soluble fertilizers apply 75- to 100-ppm nitrogen with every irrigation or use 150 to 200 ppm as needed. Controlled-release fertilizers are commonly applied as a top-dress onto the media surface using the medium recommended rate on the fertilizer label or incorporated into the growing media prior to planting at a rate equivalent to 1 to 11/4 pounds of elemental nitrogen per yard of growing medium.

The best quality is achieved when plants are grown in full sun or in greenhouses with high light intensities; 5,000 foot-candles is sufficient. When produced under lower light levels, the stems will become leggy and overall plant quality will be reduced.

Throughout the majority of production, it is not usually necessary to control plant height, but as the shoots with the flower buds begin to elongate (the last few weeks of production), it is beneficial to implement some type of height control. In many cases, stem elongation can be reduced by spacing the containers slightly farther apart beginning approximately one month before the anticipated market date. If plant growth regulators are necessary, apply them just as the stems are beginning to elongate rapidly. One or two foliar applications using a tank mixture of 2,000-ppm daminozide (Dazide or B-Nine) plus 3-ppm uniconazole (Concise or Sumagic) are effective in controlling stem elongation.

Insects and Diseases

Dianthus are susceptible to several insect pests including aphids, caterpillars, spider mites and thrips, but these pests rarely become problematic. Although they generally can be grown without the incidence of plant pathogens, dianthus under certain circumstances are susceptible to numerous diseases including Botrytis, leaf spots (Alternaria, Cladosporium, Heterosporium and Phyllosticta), rust and pathogens that cause the plants to appear wilted (Fusarium, Pythium and Rhizoctonia). They are most susceptible to these diseases when they are grown under cool and wet conditions, such as going into or coming out of winter dormancy or following extended periods with wet foliage. Growers should utilize routine scouting programs to detect the presence of insects and diseases early and to determine if and when control strategies are necessary.

Forcing

'Coconut Punch' can be forced into bloom for mid season sales by following a few guidelines. When large containers (1 gallon) are being produced, it is beneficial to plant them during the late summer of the previous year, allowing them to bulk up prior to over-wintering. Aim to have the plant canopy cover approximately two-thirds of the media surface before overwintering them. Planting large container sizes of dianthus in the spring often results in small blooming plants before the container has reached a marketable size. Spring planting vernalized liners is acceptable for the production of small container sizes.

Dianthus has an obligate cold requirement for flowering. They will flower sporadically and have low bud counts when vernalization is omitted. As mentioned above, it is recommended to 'bulk up' large containers before overwintering them. Provide at least six to nine weeks of cold temperatures (less than 44¡ F) before forcing them in the spring. Following the cold treatment, they will flower under any photoperiod (day-neutral plants) and can be forced into bloom under natural day lengths. The length of the photoperiod does not have any effect on the time to flower or the number of blooms produced, but they will flower slightly faster when they are grown under high light intensities.

The time to bloom after vernalization depends on the temperature the plants are grown at. 'Coconut Punch' grown at 68¼ F will flower in approximately seven weeks, while plants that are grown at 60¡ F will reach flowering in nine to 10 weeks. Producing them at cooler temperatures increases the time to flower, but improves the overall quality characteristics of the plant, such as the color intensity of the foliage and flowers.

Availability

Dianthus 'Coconut Punch' is available exclusively from Walters Gardens Inc., Zeeland Mich. (www.waltersgardens.com). Finished containers can be purchased from many reputable finished growers or garden centers throughout the country.