Get It Growing: Little Ruby alternanthera gives summer color

By DAN GILL

LSU AgCenter Horticulturist

The foliage of ornamental plants generally plays a supporting role to their colorful flowers. Leaves, in all their many different shades of green, typically provide a backdrop for the flowers that delight the eye and dominate our attention.

But this is not always the case. Many of our best and most reliable plants that brighten our summer gardens rely on colorful foliage, rather than flowers, to provide the color we all crave in our landscapes.

Plants grown for their attractive foliage will often stay more reliably colorful than flowering bedding plants. Flowers can come and go, but the foliage is constant. As long as these plants are alive and healthy, they provide color. And you don’t have to deadhead faded flowers to keep them looking fresh and neat.

Colorful foliage plants also combine beautifully with flowering bedding plants.

Alternanthera is a genus that has long provided a variety of bedding plants grown for their attractively colored foliage. Called by the common name Joseph’s coat or their genus name alternanthera (al ter NAN ther ah), these plants have been used by gardeners since the Victoria period to create beds of color laid out in simple or complex patterns.

Many different types of ornamental alternantheras are available to gardeners. Depending on the type, the foliage may be burgundy, purple, chartreuse or yellow or variegated in white or shades of red, orange, hot pink and gold. They may grow relatively tall — up to 3 feet — or stay short and low to the ground. Some types do well in full sun while others prefer some shade. They are well adapted to the heat and humidity of Louisiana summers.

The LSU AgCenter Hammond Research Station has done extensive trials and evaluated many types of alternanthera for a number of years. And as is often found when doing variety trials, all alternantheras do not perform equally well.

One alternanthera, Little Ruby, has consistently demonstrated outstanding characteristics that make it particularly worthy of planting.

Little Ruby alternanthera (Alternanthera dentata Little Ruby) is among the very best alternantheras for Louisiana gardeners to plant. Because of its outstanding characteristics, it is a spring 2013 Louisiana Super Plants selection.

Several things set Little Ruby apart from other alternantheras. It is a compact grower staying around 12 inches or less, making it useful in containers and in the front of flower beds. It maintains its attractive, low-mounding growth habit through the summer growing season, never getting rangy or out of shape.

Unlike most of the lower-growing, compact alternantheras, the leaves of Little Ruby are relatively large at an inch or more in length. This gives the plant more impact in the landscape. And the color of the foliage is outstanding and dramatic.

Deep shades of burgundy and purple predominate, but the back of the leaves is a rich ruby red. The color never fades through the scorching heat of mid- to late summer, and they look just as great at the end of summer as they did when you planted them.

This heat-loving plant is best planted after danger of frost, so now through midsummer is a great time to add it to containers and flower beds in your landscape.

Little Ruby is most colorful and compact when grown in sunny locations that receive six to eight hours of sun each day, although it can also be grown in slightly shadier spots. It may grow a little taller, and the color may not be quite as intense. Avoid planting in shady areas.

Before planting, prepare beds with generous amounts of organic matter. Work 2 to 4 inches of compost, composted soil conditioner or composted manure and a general-purpose fertilizer (follow package directions) into the upper 8 inches of the soil. Then rake the bed smooth.

It is best to plant Little Ruby (and most bedding plants) into beds built up 6- to 8-inches high to ensure good drainage.

Plant transplants into the garden at a spacing of about 12 inches. This allows the plants to develop and spread to fill the area where they are planted. Do not plant them any deeper than they were growing in the pots because this can make them more prone to crown rot.

Little Ruby is very heat and stress tolerant. Water them deeply as needed during the first few weeks while they are getting established.

Once established, however, they are relatively drought tolerant – they do not need constant irrigation through the summer. Overwatering can lead to problems, so make sure the plants really need to be watered before you do.

Beds should be mulched 1- to 2-inches thick with your favorite mulch. This will help conserve moisture and reduce the need to irrigate. Mulches also make a planting look more attractive and reduce weed problems.

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. New selections are announced and promoted each year in spring and fall.

Louisiana Super Plants have a proven track record having gone through years of university evaluations and years of observations by green industry professionals.

Home gardeners and professional horticulturists alike can benefit from using Louisiana Super Plants. Louisiana Super Plants are “university tested and industry approved.”

To see a list of nurseries participating in the Louisiana Super Plants program, go to www.lsuagcenter.com/super plants.

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