Plant Profile: Azaleas

Evergreen azaleas are the backbone of spring color in the Mid-South. Our climate and soil are perfect for these plants that transplant well, and are easy to grow and propagate. They are unsurpassed as flowering shrubs.

Azaleas like a fair amount of shade, and well-drained slightly acidic soils, both of which are prominent in established neighborhoods in the Mid-South. They do not like competition from shallow rooted trees such as maples and magnolias, but most hardwoods like oaks are fine shade providers for azaleas. Before planting, soils should be amended with soil conditioner (ground pine bark), red sand, and leaf mold, if available. These amendments acidify the soil and provide good drainage, which azaleas need to thrive. They should be planted high or in slightly raised areas, never in low spots, because poor drainage can affect their growth.

The diversity of the azalea is staggering. The blooms en masse are showy and come in many vivid colors. They can overpower and clash with neighboring plants so coordination of colors and other plantings' bloom times are important.

In the Mid-South, some of the best performing cultivars of evergreen azaleas are hybrids, which are usually defined by the place or persons involved in the breeding. Time-tested performers are found in the Kurume, Glenn Dale, Back Acres, and Kaempferi hybrids. The Satsuki group of azaleas work well here, are generally smaller in stature, and flower in May. Recently the Encore azaleas have become widely available, with taut blooms that continue all season until the fall. Kurumes are April-flowering azaleas. Although they have smaller flowers, they make up for this in quantity of blooms. Only two Southern Indian hybrids work well in the mid-south, and these hybrids grow as far north as New England: ‘Mrs. G. G. Gerbing’ (white) and ‘George L. Taber’ (light pink).

The Glenn Dale azaleas are another popular group of hardy evergreen azaleas with flowers as big as the Southern Indians, and all are cold hardy. These are bred by B. Y. Morrison at the USDA in Maryland. This is another staple for mid-south gardens. The common ‘Fashion’ (salmon pink), ‘Glacier’ (white), and ‘Amy’ (pink) are all members of the group, which has 454 cultivars.

In terms of design, planting in drifts or groups provide a more visually appealing display than planting individuals. Using white azaleas to blend and soften the strong colors gives a long season of color that blends nicely. For example, a combination of Rhododendron poukhanense, ‘Herbert’, ‘Gwenda’, and ‘Martha Hitchcock’ overlap bloom times.

In terms of plant health, azaleas are generally carefree; however, there are two common problems that can affect azalea growth in the midsouth, but can be easily remedied. Chlorosis of the leaves is a condition in which veins remain green while the leaves turn yellow. This is generally a sign of iron deficiency and regular evaluation of soil pH levels is suggested. Azaleas prefer acidic soil and, if grown in a less-than-optimal pH, often have trouble absorbing iron. In addition to adjusting the pH, ironite can be added if problem persists.

An insect called lace bug is the culprit for the second common problem. This pest, with lacy long wings, will cause the upper surface of a leaf to look dusty because it will have so many tiny spots. The easiest and safest method to control these insects is with imidacloprid. Sold to homeowners as Bayer Advance Tree & Shrub formula, one soil drench in late March or early April will keep these pests in check for the balance of the season.

After these plants flower, cutting them back and fertilizing them will increase next year’s bloom count. Gently controlling the shape so they look natural and maintain lower branches keeps them much healthier than gasoline-powered or scissor-type hand shears. Mulch after cutting them back.

Posted by Kristen Rambo at 7:00 AM
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