Kauai White Torenia in the shade garden at the Hammond Research Station in October 2013. (Photo by Allen Owings)

For Release On Or After 04/11/14

By Dan Gill
LSU AgCenter Horticulturist

Spring is here, and it’s time to plant warm-season bedding plants into our flower gardens. These plants will provide color for us through the coming summer. An outstanding choice is Kauai series torenia (Torenia fournieri), a Louisiana Super Plant selection for spring 2014.

Here in Louisiana, summer bedding plants must tolerate extreme heat and humidity and have the stamina to hold up over our long summer season. Torenias thrive in the Louisiana summer no matter how hot, humid or rainy the weather. This is not surprising when we consider that the original species is native to forests in tropical Southeast Asia. They bloom from spring to late summer or early fall and prefer partly shaded beds.

Louisiana gardeners have been growing torenia at least since the 1970s. And they were likely grown by gardeners well before that. The original species is a nice lavender-blue color with very dark patches on the face of the flower (this has led to the occasionally used common name of “summer pansy”). The throat has a small, bright yellow patch – a guide for pollinating insects.

The common name, wishbone flower, comes from the way the stamens grow. The two stamens each grow from opposite sides of the flower. They meet in the middle and form a structure that looks just like the wishbone of a chicken. You can easily see this when you look down into a flower throat.

Torenia is a bushy plant with soft, succulent stems and serrated leaves of medium green about an inch long. The height is around 12 to 16 inches. Abundant tiny seeds are produced, and under the right conditions it is not unusual to see volunteer seedlings show up in locations where torenias grew the previous summer. These are easily removed or transplanted to locations where you want them to grow. I’ve never known the plant to become a nuisance.

New colors were introduced in the 1980s when the Clown series was released. It included rosy pinks, light blue and magenta-purple flowers. More recently, the Panda series has been commonly available. Both of these series were more compact than the original species and produced a greater number of flowers in a wider range of colors.

Kauai torenia

The Kauai series is the most recent introduction in torenia breeding and was put into trials at the LSU AgCenter Hammond Research Station for evaluation. The outstanding performance of this series over the past few years was so impressive that it has been named a Louisiana Super Plant selection for spring 2014.

These plants perform best in a location that receives part shade to part sun. Kauai torenias will grow in sunny beds and even in shady spots. But plants in the sun have more faded foliage, and plants in the shade are taller and don’t bloom as profusely. A location that gets about a half a day of sun – morning or afternoon – or a location with plenty of dappled light or high shade provides the best results.

Kauai torenias are a great alternative to impatiens in shady areas. Concern continues about the new downy mildew disease that is so destructive to impatiens (Impatiens walleriana). Torenias are not prone to any major insect or disease problems and remain healthy and attractive through the summer. About the only care they need is regular irrigation if the weather is dry.

As with all bedding plants, a well-prepared bed will encourage the plants to perform their best. Till the bed about 8 inches deep. Next, spread a 2- to 4-inch layer of organic matter, such as compost, over the bed and scatter a light application of a general-purpose fertilizer. Thoroughly work all of that into the soil, rake the bed smooth, and you are ready to plant.

These compact plants grow to be 10 to 12 inches tall and about 14 to 16 inches wide. Space the plants about 12 inches apart when planting them into the garden. Torenias can be planted in the spring as soon as the chance of freezes is past and the weather is warm and settled – generally around April or May. You can continue to plant torenias through the summer – they will establish well even if planted in the intense heat of midsummer. After planting, mulch the bed to conserve moisture and help control weeds.

What really sets Kauai series torenias apart is the improved color range of the flowers. Colors in the series include Kauai Blue and White, Kauai Deep Blue, Kauai Lemon Drop, Kauai Magenta, Kauai Rose, Kauai White and Kauai Burgundy. Notable are Kauai Lemon Drop and Kauai White. Lemon Drop produces white flowers with yellow patches on each of the petals. And, Kauai White produces flowers that are a unique, clear, clean white with just a tiny spot of yellow in the throat.

Kauai torenias combine beautifully with shade-loving perennials and look great planted with other summer bedding plants that like part shade, including begonias (such as the Louisiana Super Plant selections BabyWing White and BabyWing Pink) and caladiums. They are also an excellent choice for planting in containers.

The Louisiana Super Plants program is an educational and marketing campaign of the LSU AgCenter that highlights tough and beautiful plants that perform well in Louisiana landscapes. To see a list of nurseries participating in the Louisiana Super Plants program, go to www.lsuagcenter.com/superplants.