Downey mildew has become a problem on impatiens in recent years. Fungicide control options are difficult for most homeowners. (Photo by Allen Owings. Click on photo to open, then right click to download image.)

BabyWing begonias add colorful flowers to shady landscapes. (Click on photo to open, then right click to download image. Photo by Allen Owings.)

News Release Distributed 04/12/13

By Allen Owings
LSU AgCenter horticulturist

HAMMOND, La. – As the peak of the spring bedding plant season arrives, we may need a few warm-season flowers in our shade areas around the landscape.

Most of our warm-season flowers prefer full sun or more sun than shade, but we have many great bedding plants that will produce pleasing flowers and foliage for those shaded areas through fall. Examples are torenia (wishbone flower), different types of begonias, caladiums, coleus and impatiens.

Impatiens are the warm-season flower for shade. Overall, it the most widely sold warm-season bedding plant around the country. Morning sun is fine, but they will need shade from late morning through late afternoon, if possible, to perform best. Plants will flower throughout the warm season of the year. Plant impatiens in midspring in well-drained, moist soil.

Great companion plants include coleus, begonia, torenia and caladiums. Most impatiens will get 18 inches tall. Sometimes they will get tall and leggy when planted too close together. Prune them lightly in late summer, and plants will bloom again in two weeks. Many flower colors are available. You can now get impatiens with trailing growth habits.

We need to be cautious with impatiens in 2013. You may have noticed that impatiens did not perform well, or even died, in your landscape in 2012. There is, unfortunately, a new disease plaguing impatiens, not only in Louisiana and other parts of the Southeast but across the vast majority of the country. Impatiens downy mildew is Plasmopara obducens, and the garden type impatiens that we most commonly use are very susceptible to this disease. New Guinea impatiens are disease-tolerant and good plants for shade in Louisiana.

Downy mildew symptoms appear as a gray discoloration on the bottom sides of leaves. The new growth could be yellow and curling downward. The infected leaves will fall off, resulting in severe defoliation. Fungicide control options are difficult for most home gardeners.

The companion plant for impatiens that we normally use in the shade garden is caladiums. These plants can be purchased as bulbs or bought already growing in containers. Caladiums provide colorful foliage in the shade garden – green, pink and red are the most common. Caladiums are grown for their leaves, and the lighter-colored varieties work best in shady settings.

Dragon Wing and other type begonias also do well in Louisiana shade. They are promoted as more sun-type plants in northern climates, but Dragon Wing begonias need shade here.

Begonias are available in many shapes, sizes and flower colors. Foliage colors include green, bronze and red. Typically, the greener-foliaged begonias do best in or require shade while the reddish and bronze begonias tolerate some sunny areas. Rum, Brandy, Whiskey, Vodka and Gin are the varieties in the Cocktail series of begonias – a longtime favorite in the South.

You could seriously consider the BabyWing begonias. These are a Louisiana Super Plants selection. BabyWing has bigger foliage on bigger plants than you may expect by looking at the name. Plants reach about 18 inches tall, and flowers come in pink and white. A bronze-foliaged variety is new for 2013. Partial shade is a great planting location for them.

Coleus have traditionally been shade plants, but many new varieties are being promoted for sunny locations. Older seed-propagated varieties, such as Wizard and Rainbow, are good for shade. In addition, the large-foliaged Kong series is an impressive grower.

Coleus, like caladiums, are grown for foliage enhancement in the garden. The sun-type varieties of coleus perform just as well in shade as they do in full sun – but the foliage color is not as impressive.

Torenia, also called wishbone flower, is a great underused shade-performing bedding plant for blooms spring through fall. They have no problem with humidity, either.

Duchess, Summer Wave and Kauai torenia are popular. Flower colors include white, pink, purple, lavender and yellow. They are not tall – usually 12-14 inches. Plant them 1 foot apart, although the trailing types may need 18 inches between individual plants. No deadheading is needed – they are no-fuss, no-care plants.

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.