Heat-tolerant Plants Available To Provide Color In Summer Gardens

Daniel Gill, Merrill, Thomas A.  |  5/26/2005 11:12:31 PM

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Get It Growing News For 06/03/05



By Dan Gill
LSU AgCenter Horticulturist400x444
Successfully creating colorful flowerbeds and container plantings for summer depends a lot on which plants you choose. Fortunately, a lot of attractive and colorful heat-tolerant plants are available to do the job.

A large part of the research that the LSU AgCenter does on bedding plants is carried out in trials at its Burden Center in Baton Rouge. This research evaluates the performance of different types of bedding plants and also compares different varieties of the same bedding plant in typical Louisiana growing conditions.

Here is information on some of the plants that performed well in trials and can be planted throughout the summer.

Zinnias have been a standard in summer flower gardens for a long time. The typical garden zinnia (Zinnia elegans) that many of us are familiar with has more than its share of insect and disease problems, which often leads to disappointment.

A different species of zinnia, however, called the narrow-leaf zinnia (Zinnia angustifolia), is far more insect and disease resistant and rarely has major pest problems. It is a low-growing, sprawling plant that produces multitudes of 1-inch single daisy flowers in orange, yellow or white. Performance in sunny areas is outstanding, and the plants reliably hold up through the intense heat and rain of summer.

Two issues with the narrow-leaf zinnia are the limited color range and small flowers. To improve this, plant breeders have crossed the garden zinnia with the narrow-leaf zinnia. The best results of these efforts, so far, are the Profusion zinnias.

The Profusion zinnias have received top marks in performance at Burden. They produce short, compact, ball-shaped plants covered with flowers throughout the summer. The flowers are larger and come in more colors than narrow-leaf zinnias, but the plants have inherited the pest resistance and compact habit of that species. The original colors released were Profusion White, Profusion Orange and Profusion Cherry. New for this year are Profusion Fire (brick red) and Profusion Apricot.

Torenia, or wishbone flower (Torenia fournieri), has been one of my favorite summer bedding plants for a long time. You simply can’t beat their reliable performance in sun to part-shade. The neat, compact plants stay under a foot tall and come in various shades of lavender-blue, purple, pink and white.

When Summer Wave torenia became available several years ago, a whole new type of torenia entered the gardening scene. Producing unusually large flowers of medium lavender-blue, the plants have a vigorous low spreading habit. One plant can easily cover a 2 foot by 2 foot area (or larger), and they never stop blooming. Their stamina is everything you could ask for, since they will still be blooming heavily when the first freeze of December hits. Other colors are available these days, and new for this year, Proven Winners has released the Catalina torenia series, which look like they will be similar.

The most commonly grown type of perilla (Perilla frutescens) has aromatic foliage that is ruffled and dark purple, and it can be used as a culinary herb as well as an ornamental. A new variety called Magilla perilla is different and rapidly becoming popular. The dark purple leaves are highlighted by an area of pink or vivid magenta in the middle. It closely resembles coleus (both are in the mint family), grows to be 2 feet tall or more and thrives in full sun to part shade. The colors are more muted in shadier areas.

A wonderful, relatively new plant called angelonia (Angelonia angustifolia) performs beautifully in sunny beds. Early cultivars tended to be rather tall and gangly. Newer, improved types are more compact, produce more flowers and come in more colors. They are outstanding performers in the summer flower garden and will bloom until first freeze. Angelonia may survive mild winters in protected locations. Look for AngelMist and Carita series, which come in a variety of colors.

Coleus, which had long been used in shady beds, began to be part of our sunny gardens with the release of new sun-tolerant types in the 1990s. This trend has continued, and virtually all the new coleus varieties released in recent years have been sun tolerant. Bucking the trend, however, is the new Kong series of coleus, which prefer shade.

Kong coleuses come in five different colors and sport leaves far larger than other types of coleus. You will find that the bold texture and bright colors of the large leaves make a dramatic addition to shady beds.

If you are adventurous, try out brand new impatiens called the Fusion series. They don’t have a proven track record here – but they are worth an audition. Similar to other African impatiens (like Jungle Queen and Jungle Gold), they produce flowers in shades of yellow and orange, colors not often found in shade-loving plants. If they hold up to our summer heat, they will be a wonderful addition to shady flowerbeds.

Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at www.lsuagcenter.com. A wide range of publications and a variety of other resources are available.

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Contact: Dan Gill at (225) 578-2222 or dgill@agcenter.lsu.edu
Editor: Tom Merrill at (225) 578-2263 or tmerrill@agcenter.lsu.edu

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