#TeachingTuesday: Azaleas

Even if you don’t do any gardening or landscaping at all, if you live in the south, you probably know what an azalea looks like. In April, you can drive around any neighborhood to see the brightly colored shrubs completely covered in blooms. Many azaleas originated in Japan, but are now icons of the southern garden, with both heirloom and new varieties available. There are also beautiful native varieties from right here in the Carolinas.

Photo credit: Josh Whitener

The Right Plant for the Right Place

Azaleas are woodland understory shrubs, so they do best in dappled shade, protected from winds and harsh sunlight. Azaleas planted in full sun are highly susceptible to lace bugs, which feed on the sap through the leaves. In a bad infestation, the leaves may turn a silvery white color, and over time the health of the shrubs will decline. Avoid having to use chemicals to protect your plants by planting them in an appropriate location from the beginning.

Azaleas tend to develop root rot easily if the soil is not well-drained, but they are also shallow-rooted, and may require irrigation during dry periods in some landscapes.

When Do I Prune My Azaleas?

The answer is: it depends! Before you prune any tree or shrub, you should always ask yourself what the goal is. If you’re not sure, you probably don’t need to prune! Azaleas have an interesting branching structure which makes them more challenging to prune than many other common shrubs. Essentially, there are two main methods for proper pruning of azaleas–one for general shaping and thinning, and one for rejuvenating old, overgrown shrubs.

Thinning or “Pocket Pruning”: identify the branch or stem that needs to be removed, whether it is dead, diseased, leggy, broken, or just needs to be removed to improve air circulation within the shrub. Trace the stem back to where it connects to the main trunk or another branch, and prune it close, without leaving a stub. Thinning should be done AFTER blooming in the spring, in order to preserve the next year’s flowers.
Rejuvenation/Renewal Pruning or “Heading”: This pruning method is more severe, and should only be done if absolutely necessary, as it will alter the natural shape of the shrub. When azaleas become very old and overgrown, sometimes the best thing to do to improve their health is to cut them back to about 6-12″ above the ground and allow them to regrow. This type of pruning is done without regard to the location of the branch unions, so it will look very unattractive until the shrubs begin to grow back. This should be done in the late winter, before the new growth begins, which means that the flowers will be sacrificed for the year.

Azaleas look best in naturalistic masses, under trees that provide protection from the sun.
Photo credit: Marco Acevedo

ID Tips

Most everyone knows an azalea when they see one, but here are a few tips for when they are not blooming:

The leaves are elliptical in shape, ranging from very small to 1 or 2 inches long, and area covered with very fine hairs. On some varieties it may feel like a velvety fuzz, and others it may feel like sandpaper.
The twigs are covered in fine reddish-gold hairs.
The branches and twigs grow in “trusses,” which means that one branch will reach a certain point, then suddenly branch out into a cluster of branches radiating from one point. Each of those branches will grow, then branch off into their own clusters.
There are both evergreen and deciduous varieties of azalea, and some azaleas even bloom twice in one year, once in the spring, and once in the fall.

Encore azaleas blooming in November.
Photo credit: Tony Stewart

#TeachingTuesday: Loropetalum

Spring is really here! We are seeing so many beautiful flowering plants in the landscape this week. To finish out March, we will be covering the loropetalum shrub, or Chinese fringe flower (Loropetalum chinense). This plant has been in the United States for almost 150 years, but recently many new colors of foliage and flowers have been released, which has made it more popular. They typically bloom the most from mid-March through mid-April, but amazingly, loropetalum can bloom sporadically throughout the entire year!

Loropetalum is an evergreen shrub with small leaves that may be anywhere from a medium green to burgundy to almost black in color. The flowers range from white to many shades of hot pink and fuchsia, to bright red. Loropetalum may be grown as a hedge, a small to large shrub, or even a small ornamental tree, depending on the cultivar and how it is pruned. While it will tolerate heavy pruning, it will be a healthier and more attractive plant if maintained in a somewhat natural form. Any pruning should be completed in the spring after flowering in order to promote the best blooms for the following year. Pests and diseases are rarely an issue, but if planted in wet, boggy soils, loropetalum shrubs will likely develop root rot.

ID Tips

Loropetalum flowers look like small little tassels of fringe, with lots of long, thin, straplike petals. They look similar to the flowers of witch hazel, but witch hazels are deciduous, and bloom before the leaves bud out, while loropetalums are evergreen.
Loropetalum leaves are small and roundish to ovate (egg-shaped), arranged in an alternating pattern along the stems. The leaf surface is rough, and may feel a bit like sandpaper. The leaf margins (edges) may be very finely toothed, or smooth.
The stems are densely “pubescent,” or covered with tiny hairs.

Note the alternate pattern and the tiny hairs covering the stem and leaves.

#TeachingTuesday: Camellia and Hellebore

What a beautiful St. Patrick’s Day weekend, reaching the upper 70’s on Friday, and even though the temps dropped back down, we had clear sunny weather Friday through Sunday! We’re doubling up today to get back on schedule, covering two gorgeous late winter/early spring bloomers: camellia (a shrub) and hellebore (a perennial).

Camellia

The camellia that everyone is noticing this time of year is Camellia japonica. It’s a beautiful evergreen shrub with dark, glossy green leaves and large rose-like flowers that range from single (only one row of petals), to full double varieties with rows and rows of petals, similar to a peony. Camellia sasanqua looks similar, but has smaller leaves and flowers, and the flowers only come in single or semi-double forms. It blooms in the fall.

Camellias prefer well-drained, rich soils and can be slow to establish due to their slow growth. They should be protected from harsh sunlight and heavy winds in order to perform at their best.

Camellia sasanqua, photo by Herbie Champion

Maintenance and ID Tips

Camellias should never be sheared.
Occasional pocket pruning can be done to gently shape the shrub and increase air flow within the canopy.
Camellias are recognizable by their thick, leathery, glossy, leaves with finely toothed edges. There are no thorns or spines.
The flowers are very recognizable, even though there are a varieties of types and colors available. The flowers are very large, and bloom much earlier in the year than most flowering shrubs do.

Hellebore, AKA Lenten Rose

Hellebores (Helleborus spp.) are excellent perennials for dry shade gardens. They bloom during a time when most perennials are dormant, so they really make a statement in the late winter/early spring garden! Shade resistant, drought-resistant, deer- and rabbit-resistant…these are tough plants. Some varieties self-seed, so gardeners can transplant new ones that sprout up each year. It usually takes 3 years for a plant to flower if grown from seed, but if plants are purchased from nurseries, they are generally old enough to flower the first year after planting.

Maintenance and ID Tips

Cut back ratty or wind-burned foliage in late spring as needed. The flowers last a long time, but may but cut back when they are no longer attractive. Leave the flower stems until the seeds develop and fall if new plants are desired.
A general slow-release fertilizer may be applied in late winter when the new growth starts to appear, if desired.
The evergreen leaves are thick, leathery, dark green, and sometimes shiny. They have serrated edges which may cause scratches or cuts on skin because the leaves are so stiff.
The flowers last a long time because the outer petals are not actually petals, but “tepals”, which are sepals that look like petals (sepals are the protective coverings of the outside of a flower bud before it opens–think of the little green leaflike parts on the base of a rosebud). Because they are meant to protect the bud, they are much tougher than petals and can survive cold temperatures.
The flowers often nod like bells on the flower stalks.
The common name, lenten rose, refers to the fact that they are often in bloom during Lent.

Helleborus (Rodney Davey Marbled Group) ‘Penny’s Pink’ under Cornus stems in John Massey’s garden at Ashwood Nurseries © Copyright Jonathan Buckley

#TeachingTuesday: Red-Twig Dogwood

Usually, when people think of “dogwoods”, they think of the eastern flowering dogwood (Cornus florida), a small, native, understory tree with showy white or pink blooms in the spring. But did you know there are lots of different kinds of dogwoods, including both trees and shrubs? This morning, our crews were trained in identification and maintenance of red-twig dogwoods (Cornus sericea), which are beautiful shrubs with brilliant red stems that look absolutely stunning in the winter–especially in the snow! The stems can also be cut and used in holiday floral arrangements.

A winter landscape at JC Raulston Arboretum: Red-twig dogwoods in the foreground with maidengrasses and pine trees in the background.

Red-twig dogwoods, also known as red-osier dogwoods, are native to most of Canada and the western and northern regions of the United States. They are shrubs that truly have 4 seasons of interest. In the spring, they leaf out with fresh green foliage; in early summer, they bloom with clusters of tiny white flowers that mature into red berries; in fall, the leaves develop a deep, purplish-red color; and in winter, the leaves drop to reveal the brilliant red stems. They can grow up to 9 feet tall and wide if left natural, but typically a rejuvenation pruning schedule is followed to retain the bright red young stems (more on this below). They tolerate sun to part-shade and wet to dry soils, support many species of local insects and wildlife.

Maintenance

Red-twig dogwoods are pretty low-maintenance shrubs. In natural areas where size is not an issue, they can be left to their own devices. However, as the stems mature, they will lose the intensity of the red color, and will eventually turn gray after a few years. So, periodically, the old stems need to be pruned out. Ideally this would be done once per year in the winter, and the oldest stems that are starting to lose their color would be pruned all the way to the ground. Be careful not to prune new shrubs that have been planted within the last year, and don’t remove more than 1/3 of the total stalks in one year.

ID Tips

The bright red stems are pretty good indicator that a shrub is a red-twig dogwood (or closely related species).
The stems will have light tan “lenticels”, which are small, corky bumps or lines on plant stems or trunks that allow gases to interchange between the air and the interior plant cells.
The leaf shape and venation (vein pattern) are similar to eastern flowering dogwood, although the leaf may feel thicker and tougher.
The flower clusters are white, and each floret (tiny flower) has 4 petals and a reddish center.
In late summer, the flower clusters will develop into clusters of red berries, which will persist through the fall.

Notice the pattern of light tan dots (called “lenticels”) covering the stems.