New landscape plants perform well in shade garden trials

Richard C. Bogren, Owings, Allen D.

News Release Distributed 08/09/13

By Allen Owings

LSU AgCenter horticulturist

HAMMOND, La. – Evaluations of landscape plants at the LSU AgCenter Hammond Research Station include a shade garden area where varieties of new ornamental plants or improved varieties of older ornamental plants are evaluated under partially shaded to shaded conditions. Shade is provided by a stand of spruce pine, loblolly pine and oak trees.

Plants in the shade garden evaluated year to year generally include hosta, caladium, torenia, begonia, coleus, New Guinea impatiens along with various others.

Many gardeners aren’t familiar with perennial begonias, but these beautiful foliage plants make nice shade plants for containers or landscape beds. They’re especially appropriate when soil is high in organic matter and drainage is good. This also protects them some from colder winter temperatures that can sometimes threaten their perennial hardiness in the lower part of zone 8B.

One of the objectives of our U.S. Department of Agriculture-Agricultural Research Service cooperators is to “develop perennial begonia varieties for temperate zones by adding ornamental traits from tropical germplasm into cold-hardy species that have rhizomatous roots.” Of 30 varieties being studied, a few are looking promising – these include Bashful Bandit, Bandit, Morning Mist, Swallowtail, Bethlehem Star and Green Fountain.

Torenia, also called wishbone flower, is a great substitute for impatiens and caladiums in the shade garden. These plants work especially well on the front borders of these beds because of their short height and spreading, ground cover-type habit. The Kauai variety from seed and the vegetatively propagated Summer Wave are industry standards.

Torenia is mostly for shade to part sun and grows 10-12 inches tall by 10-12 inches wide. Summer Waves are wider and work well in baskets. You normally plant these in the spring after danger of frost, but you can continue planting them through the summer. Plants flower spring through fall and do not need to be deadheaded or have old flowers removed to continue blooming.

Torenia have great potential for increased use as an impatiens substitute or as a lower-maintenance bedding plant.

Geraniums are not widely thought of for shade in the Louisiana landscape, but we are seeing some varieties perform well even into the summer. This year, a new seeded line of geraniums from American Takii is being trialed with good results.

The Divine series of New Guinea impatiens was the first group of seeded-type New Guineas. Ten flower colors are available. This series also has two bronze foliaged varieties – scarlet and orange. Today’s New Guinea impatiens are much better landscape performers than those first introduced 25 years ago. Divines will establish fast in the warm season-landscape. They are uniform and well-branched and offer big flowers to brighten shaded gardens.

A popular traditional bedding plant for shady gardens is coleus. Many new types of coleus are sun-loving, sun-adapted and sun-recommended. But new shade types are also on the market.

New seeded coleus varieties coming for 2014 include the Kong Jr. coleus and the Mighty Mosaic. The Kong Jr. series from Ball Ingenuity debuted at California Spring Trials this year and is a smaller-growing, less-flowering form of the original Kong coleus. Foliage colors are lime green, green halo, rose and scarlet. Scarlet is the latest to bloom. Mighty Mosaic from PanAmerican Seed is a 20- to 24-inch grower in a Southern landscape. It has an unusual multicolored leaf pattern.

Gingers are popular foliage and summer-flowering tropical plants for the shade. One ginger relative, the Siam tulip, has been impressive in Hammond this summer. Varieties being evaluated include Emerald Chocozebra, Deep Pink Grande, Blushing Star, Kimono Deep Rose and Kimono Pink. These deciduous, tropical perennials require well-drained, moist soil. In the landscape, they reach 18-24 inches tall.

Hosta evaluation is also continuing in the shade garden. Since 2009, Yan Chen, a research horticulturist at the station, has evaluated more than 65 hosta varieties in shade studies. The top 10 based on her research results have been Iron Gate Delight, Stained Glass, Fragrant Bouquet, August Moon, Aureo Marginata, Francee, Albo Marginata, Krossa Regal, Guacamole, and So Sweet. Varieties that have traditionally not returned well from winter dormancy include Blue Angel, Blue Mouse Ear, Cherish, Ginko Craig, Hadspen Blue, Medio Variegata, Mini Blue, Samual Blue, Moon River, Sun Power and Wheaton Blue.

You can see more about work being done in landscape horticulture by visiting 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 at both sites.

Rick Bogren

8/9/2013 9:00:41 PM
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