The best pruning jobs begin with a goal, a determination of what needs to be accomplished–reducing size, controlling shape, rejuvenating growth. As with all pruning jobs, removing the dead and diseased wood is the first call of order. Then take a step back and look at the framework before moving ahead with your mission.
The best time to prune azaleas and rhododendrons is immediately after bloom into mid-July. If you wait too long, buds will already have formed for the following year. In general, azaleas and rhododendrons need minimal pruning.
Reducing Size
To reduce the height of an azalea while allowing it to retain its natural appearance, follow the branch targeted for removal down to a lower lateral branch, and make a cut just above the point of intersection. The cut should be slightly above where the two branches intersect so as not to cut into the tissue of the branch that will remain.
Another way of reducing the size of an azalea is to cut it back to just above a whorls of leaves. Also look for circular scars around the stem, where leaves once were. Cutting just above these areas should create good bud break. In either case, make the cut just above new buds, whether they are visible or latent.
Controlling Shape
Evergreen azaleas can be sheared back to form nice mounds if desired. If you are pruning the azalea into a mound, remember to occasionally open up the plant and let some light penetrate into the dense mass of foliage so that it doesn’t get too congested.
If you’d like to make a young azalea or rhododendron more compact and well-branched, the easiest thing to do is to pinch off the vegetative buds in spring. First take a look at the plant to familiarize yourself with the bud system. The fat swollen buds are flower buds. These form in the previous season and overwinter, and you’ll want to leave these alone. They are generally twice the size of the vegetative buds, which are the narrower, pencil-like, smaller buds.
The majority of azaleas native to North America hail from the states running down the Appalachian mountain range; from Maine to Florida. All of the North American natives are deciduous, tend to have open, loosely branched habits, are known for their hardiness, and for their exquisite fall foliage. Many are scented, with perfumes ranging from sweet to spicy.
Though azaleas in general prefer part sun and moist, humus-rich, well-drained soil, among species there is a broad spectrum of tolerance for heat, moisture, and hardiness. Flowering times are also wide ranging: from early April into August.
Following are some native species and their cultivars that can be found in the Azalea Garden.
As discussed last week, good site conditions such as a soil pH of between 4.5 and 6, soil rich in organic matter, good drainage, and a part-shade to full-sun environment including protection from strong winds are essential for the health of azaleas. Be sure to research basic information about the azaleas you are purchasing including color and bloom time, its ultimate size, growth habit, and hardiness When planting azaleas, it is important to provide enough space between them for sufficient light and air circulation. Plant labels and catalogs generally supply appropriate spacing information for both the height and width of the azalea.
Chances are that the azaleas you purchase will have been grown in a container, either in a soil-less potting medium or a mixture of composted bark and sand. While these are fine mediums for plants grown in a container, making them easier to care for, the potting mediums are very different in structure from native soil, and water will not flow freely from one to the other. Often, the native soil around the newly planted azalea will be moist while the root ball remains dry. Because of this, the day before planting, water your potted azaleas so that they are well hydrated but not too soggy.
If you have good drainage, plant your azaleas at the same level to the soil as they were in the container. The planting holes should be the same depth as the container and 3-5 times as wide, with sloping sides. Most of the roots on each azalea will be growing in the top 12 inches of the soil, extending outward rather than downward. The goal in making a wide hole is to loosen the soil in the area of maximum root growth. Remember, azaleas are a shallow rooting plant. Do not dig the hole excessively deep, otherwise the root ball will sink and settle too low. If you have clay soil, you can plant your azaleas slightly higher than grade (1 to 2 inches higher). Sometimes azaleas are planted 6 inches higher with great success. To do this, add coarse sand and leaf compost to the backfill and grade on a slight slope.
When removing an azalea from its container, take care to protect the tiny hair-like feeder roots along the main roots, which can be torn if the plant is pulled from its base straight from the container. Instead, for a small container, with one hand cup the top of the container around the stem. Tip the container upside down–cradling the plant with the cupped hand–and slide it out of the container. If the root ball sticks to the container, tap it against a firm surface to dislodge the plant from the pot. For a large container, two people may be needed to hold and tip the container or to lay it on its side and gently slide the plant out.
Azaleas are wonderful additions to the garden. They are easy to grow, look sensational, and have attractive foliage. Evergreen azaleas provide year-round interest while deciduous azaleas often have exquisite fall color and exhibit an elegant woody framework in winter.
In their native habitats, azaleas are often found growing in or on the edge of woodlands in well-drained, acidic soil that is rich in organic matter. They have a shallow, fibrous root system, which needs to be considered when caring for them. Azaleas do well in full sun or part shade (about four hours of sun). Planted in full sun, azaleas will be more compact and floriferous. When planted in part shade, they will stretch toward the sunlight and form a more graceful habit; flowers will not be as plentiful but will last longer.
When using azaleas for foundation plantings, locate them 3 – 4 feet from the building so that the roof will not obstruct rainfall and so that air can circulate around the plants. Avoid planting near highly reflective walls unless on the north side of the building or in the shade. Windy sites are problematic: in winter, winds and sun can desiccate the foliage, of evergreen azaleas especially. Deciduous azaleas are more forgiving.
Azaleas need good soil structure and plenty of organic matter so that their shallow roots will not dry out. Conversely, azaleas can be suffocated by excess water and poor drainage; soil compaction around foundations and in yards is a frequent problem. When amending the soil, it is better to prepare the entire bed rather than just the planting hole to create a uniform condition so that the fibrous roots are encouraged to spread. As a general rule, the soil should contain 5 – 10% organic matter.
Azaleas, as seen in the Garden‘s spectacular new Azalea Garden, provide home gardeners with wonderful spring color that extends from April into July (depending on the species). Evergreen azaleas provide year-round interest while deciduous azaleas often offer multi-seasonal appeal and lovely fall foliage. Azaleas are slow growing; many of them, save some of the larger deciduous natives, make good candidates for foundation plantings. By following a few simple rules, it is easy to design effectively with azaleas.
Azaleas can be planted as specimens or in groups. The royal azalea (Rhododendron schlippenbachii) not only has luminescent pinkish-white flowers in late April/early May but also exquisite rounded foliage that is arranged like pinwheels on the stems, making it an ideal specimen plant.
The native flame azalea (Rhododendron calendulaceum) flowers in late May to early June in a variety of shades from fiery red-orange to yellow-orange (as the name would suggest). Specimens can reach up to 12 feet tall and 5 feet wide and rival any large Viburnum in the garden. When planted en masse, flame azaleas create a nuanced color harmony that will brighten any landscape; they do not look congested or dense due to their graceful structure. Though deciduous, they can provide seasonal screening in your yard.
Pay attention to bloom time when planting azaleas in groups. Azaleas can generally be categorized by three bloom times: early, mid, or late season. I have visited gardens where azaleas are effectively planted so that they flower sequentially; as one azalea fades its neighbor opens, providing color for extended periods. Or, weave a tapestry by planting groups of azaleas that flower at the same time.
It’s an Azalea Garden of another color: Yellow. No, we’re not genetically engineering plants here at the Garden, we’re just planting for year round color. This new garden won’t open to the public until next Spring, but we’re hoping this beautiful image will entice you to come visit the Azalea Garden both when it opens and a year from now!
The Azalea Garden in Fall (photo by Ivo M. Vermeulen)
