Richard Bogren, Owings, Allen D.
News Release Distributed 11/16/12
By Allen Owings
LSU AgCenter horticulturist
November is prime time for cool-season bedding plants, and dianthus have been among the plants in this group gaining considerable popularity the past 10 years. Pansies have long been the most popular cool-season bedding plant, but many new dianthus varieties are making this great, under-used cool-season flower better known to home gardeners.
The two primary species of dianthus we plant in our gardens are Dianthus chinensis – Chinese dianthus or pinks – and Dianthus barbatus – sweet william.
Pinks have always been more popular than sweet william because they bloom more reliably over a long season. Planted in fall, they bloom from then until late spring or early summer. They are generally shorter, bushy plants that produce profusions of flowers in shades of scarlet, rose, pink and white.
Sweet william plants are fairly low and bushy, but they produce their flowers in large clusters on long stems like a lollipop. The main issue is that they are biennials. Planted in fall, they must go through a cold winter before they are triggered to bloom in spring. So a fall planting produces no flowers until spring. And as many gardeners have discovered, spring-planted transplants that have not been exposed to winter cold often fail to bloom.
The Telstar series of dianthus is a recommended group for Louisiana. Individual plants reach 12 inches tall and bear clove-scented flowers that are about an inch and a half across. This series has good heat tolerance, so it will last until late spring. Numerous flower colors are available in the series, and you are guaranteed success whether you choose to use them in a landscape bed or container.
The Amazon series was named Louisiana Super Plants several years ago. These were developed by PanAmerican Seed Company by crossing Dianthus chinensis with Dianthus barbatus to create an interspecific hybrid. The results are nothing short of outstanding.
Louisiana Super Plants have exceptional characteristics and performance in Louisiana growing conditions, and the Amazon dianthuses really deserve this tribute. The foliage is an unusually rich, deep green, and the narrow leaves form a mound at the base. Even when out of bloom, they provide a verdant green color in the winter landscape.
When the plants bloom, the flower stalks are similar to sweet william. The stocky flower stalks are clothed in narrow green foliage, rise about 2 feet above the basal growth and produce large clusters of colorful flowers. However, unlike sweet williams, the plants do not have to go through winter cold to trigger flowering.
The three colors included in the Amazon series, Neon Purple, Neon Cherry and Rose Magic, are brilliant and eye-catching. Neon Purple and Neon Cherry practically glow, their colors are so intense and vivid. Planted together, the colors seem to vibrate visually. You can buy each color separately and plant them together or in a combination called Neon Duo.
Amazon Rose Magic is the favorite of most folks. The large clusters of flowers go through a remarkable, yes “magical,” transformation as they bloom. The flowers open a bright white, age to a soft pink and finally finish up an intense rose. All three colors appear simultaneously in each cluster of flowers. Combine Rose Magic with blue, lavender, pink, silver and white flowers for an elegant effect in the garden or in containers.
The Bouquet and the Corona Cherry Magic dianthus are also popular and are good landscape plants that you can try across all of Louisiana.
Dianthus perform best in full sunlight but also do well in some filtered afternoon shade. Landscape beds need to be loose, well-drained and fertile. Dianthus do well at a slightly acid to slightly alkaline soil pH. They do not tolerate wet soil conditions, so it is important to adequately prepare a landscape bed and irrigate properly.
Plant dianthus during October or November on a 10- to 12-inch spacing to achieve a full landscape effect. At planting, or shortly thereafter, broadcast an application of a slow-release fertilizer over the entire bed area. Depending on plant performance, a second light application may be beneficial in early spring.
Dianthus usually last well until mid- or late spring in Louisiana and can even grow and bloom through summer with limited success. Although dianthus are perennial, they likely will perform best when treated as an annual cool-season plant from midfall through late spring.
You can see more about work being done in landscape horticulture by viewing the LSU AgCenter Hammond Research Station website. Also, like us on Facebook. You can find an abundance of landscape information for both home gardeners and industry professionals.