Alternatives in Cool-season Flowers for the Landscape

Linda F. Benedict, Bracy, Regina P., Rosendale, Roger M., Owings, Allen D.

Allen D. Owings, Regina P. Bracy and Roger Rosendale

The LSU AgCenter Hammond Research Station evaluates approximately 300-350 cool-season bedding plants in landscape settings each year from October through May.

Of the annual flowers for the cool season of the year, most people are familiar with pansies, snapdragons, petunias, garden mums and older varieties of dianthus. But there are many more.

Violas are the cousins of pansies and continue to gain in popularity. The Sorbet series of violas always perform well in landscape plant evaluations. The series blooms early and performs well from midfall through May. Planted in mass, they provide a great flower show. The blooms will last two weeks longer into the later spring than typical pansies. The new pansy for the past two years has been the trailing series called Plentifall. This series is being discontinued but is being re-introduced with new genetics under the name Cool Wave pansies.

The best of new dianthus is the Amazon series. These prolific flower producers should be planted in September, October or November. Flower heads are large and will last until mid-May. The series also has cut-flower potential. Flower colors include Rose Magic, Purple, Cherry and Neon Duo. Amazon dianthus was a Louisiana Super Plant selection from the fall of 2010.

Dwarf flowering tobacco is a good alternative cool-season bedding plant for south Louisiana. Though dwarf they still reach heights of 24 inches. Nicotianas have less cold hardiness than some other cool-season flowers. In south Louisiana they should be able to withstand winter conditions as long as plants are not exposed to temperatures in the upper 20s or lower in the first week after installation. They can be planted in mid-to-late February in both south and north Louisiana. Plants last until late spring. Flower colors available include white, lime, rose and red. They do best during the cool season of the year in full sun but will perform better into late spring, if partial shade is provided. The Nicki, Perfume and Saratoga are popular.

The LSU AgCenter has been evaluating landscape performance of columbines the past three years. The Swan and Songbird series are both propagated by seed. Columbine is a perennial normally treated as an annual in Louisiana. For the landscape, plant in flower beds mid to late fall for eight weeks of flowers in March through early to mid- May. Many flower colors are available besides the yellow or golden columbines from Texas. Varieties in the Songbird series are Blue Bird, Bunting, Cardinal Improved, Dove, Goldfinch, Robin and Nightingale. Varieties in the Swan series are Blue White, Burgundy White, Pink Yellow, Red White, Rose White, Violet White, White and Yellow. The Swan series is a Louisiana Super Plant selection for the fall of 2011.

Although tall-growing delphiniums are better known, there is a smaller variety for landscape beds. Diamonds Blue delphinium has intense blue flowers and is a new seed-propagated variety. This plant is considered a first-year-flowering perennial but should be treated as an annual. It should be planted in full sun in the fall for great flowering performance from February through May. Plants reach a height of 18 inches with a 10- to 12-inch spread so should be planted 12-14 inches apart. The LSU AgCenter has also evaluated the taller growing Guardian series delphinium. These are 36-inch tall plants with 24-inch flower plumes. Colors available are white, lavender and blue.

There is renewed interest in foliage plants for the landscape, and edible kale is a good selection for the cool season. Redbor is popular and a proven performer in the South. It was a Mississippi Medallion winner in 2005 and a Louisiana Super Plant for the fall of 2011. It is one of the most vigorous-growing and heat-tolerant kales on the market. Extremely curly foliage, early dark purple foliage and a spring height of 3 feet are characteristics of this plant. Plants seldom flower – a downfall of many of the ornamental kale plants. Greenfoliaged ornamental kales closely related to Redbor include Starbor and Winterbor.

Camelot foxgloves, also known as digitalis, are new to the market. For best results, these flowers should be planted in the fall. They produce 2-foot spikes of flowers in the spring. Flowers bloom two to three weeks before the popular Foxy variety and last two to three weeks longer. Flowers in the Camelot foxglove are lavender, cream, rose and white, with lavender, cream and rose being the better- performing colors.

The flowers of the African daisy are similar to Shasta daisies. They started being sold about 10 years ago, and new, better performing varieties continue to be developed. These plants do best when planted mid to late winter, and they last in the landscape until early summer. These transition plants can tolerate temperatures down to the upper 20s and go downhill during 90-degree days and 70-degree nights in May but still last until June. You will usually see blooms by late February to early March, and blooming continues in cyclic patterns. If you want to try to carry the plants through the summer, they need some shade and no fertilizer. Remove old flowers as they fade to extend the bloom. New flower colors and shades are available – mostly in the white, purple and lavender color ranges. The Akila series is new and has been a great performer in cool-season landscape trials. Colors in the Akila series are lavender, white and purple.

Allen D. Owings, Professor, Hammond Research Station, Hammond, La.

(This article was published in the summer 2012 issue of Louisiana Agriculture magazine.)

9/12/2012 7:49:58 PM
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