All American Hydroponics

Author: Pat Malcolm

Buying the best azalea shrub offers a gardener many choices for various landscapes. The Southern indica azalea hybrids are the most popular flowering shrubs for warm climates that includes the Formosa azaleas of white, pink, red, purple, magenta, violet, and lavender. Other outstanding Formosa azaleas are Duc DeRohan, Dutchess of Cypress, G.G. Gerbing, George L. Tabor, Madonna White, and South.

Kurume azaleas are evergreen azaleas with considerable cold hardiness and were introduced into the United States around 1915 from Japan. Japan has a climate much like mid-Atlantic and Southern States, and Kurume azalea plants thrive in these similar climates. Kurume azalea shrubs grow small waxy leaves and are considered to be dwarf azalea plants, growing 4 feet tall, but rarely some cultivars reach 6 feet in height. The flowers of Kurume azaleas bloom in colors of pink, purple, white, red, orange, and lavender, and some produce double flowers (double rows of petals). Coral bells is important as a pink azalea to plant underneath windows, and the intense flowering habit is also notable in the pink ruffles azalea and the red ruffles highlights any garden landscape planting. Snow is a pure white Kurume flowering azalea cultivar.

Satsuki azalea plants were developed in Japan as a bonsai specimen (dwarf), however, some cultivars can grow 6 feet tall. The flowers can exceed 5 inches, the size of a coffeecup saucer, and the late blooming characteristic of Satsuka azaleas offers the landscape gardener a flower that blooms after May 15 and continues flowering through June.

Compact azaleas are generally preferred for small gardens like the Satsuki hybrid cultivars that includes the Gumpo pink, Gumpo white, Gumpo red, Higasa rose-pink, and Wakebishu dark pink azalea. Satsuki azalea shrubs will flower abundantly.

The USDA began a hybridization program of azalea shrubs at Glenn Dale, Maryland to introduce landscape, cold hardy plants of flowering azalea cultivars that would extend the season for azalea bloom and offer Northern landscape gardeners new colorful cultivars of flowering azaleas. Many of these Glenn Dale azalea shrubs grow flowers similar to the Formosa hybrids. Glenn Dale azaleas bloom with the diversity of Japanese hybrids. Glenn Dale flowering azalea cultivars introduced by the USDA hybridizers have produced over 400 kinds of azalea shrubs, many available to buy through an internet nursery site. Two sensational Glenn Dale azalea hybrids are the salmon-pink Fashion azalea. The Fashion azalea can grow 6 feet tall and is covered with medium sized flowers. A pure white azalea, the H.H. Hume, is an excellent Glenn Dale azalea shrub that blooms in late April. Many Glenn Dale azalea landscape shrubs flower in May and June.

Not all azalea shrubs are evergreen, but American native azalea shrubs drop the leaves during winter and are called deciduous azaleas. In the South, these native azaleas are called fragrant bush honeysuckle or the Florida azalea (Rhododendrun austrinum) with colors of yellow, red, pink, white, yellow-orange, purple, and bicolor light up the forests or garden landscape when domesticated. The wild bush honeysuckle (Rhododendrun austrinum) is an early blooming native azalea shrub, with fragrant flowers appearing before the leaves.

The Oconee azalea (Rhododendron speciosum) flower is considered to be one of the most beautiful flowering plants in America, and the pleasant fragrance wafting through the garden landscape demands an equal appreciation as the captivating beauty of the azalea flower clusters. The Oconee azalea flowering shrub is easy to transplant from the forest, but it also is available from internet nurseries. The flower color of the Oconee azalea ranges from red to yellow-orange.

Many other species of wild, native azalea shrubs can be found growing as a native plant in America, and many of these species have been domesticated as a shrub that you can buy from internet nurseries. Some of the important native azalea species are the Pinxter-bloom azalea, Rhododendron nudiflorum; Swamp azalea, Rhododendron viscosum; Sweet azalea, Rhododendron arbrescens; Florida Pinxter-bloom azalea, Rhododendron canescens; and the red flowering plum leaf azalea, Rhododendron prunifolium.

An important native flowering azalea is called the flame azalea, however, this common name overlaps the descriptions of many specific species of wild azaleas. The name, flame azalea, was originally used to describe clusters of flowers on the azalea shrub (bush) that glowed in the spring with colors of yellow, orange, and red. These various species of flame azaleas occur and grow in forests from Ohio to Georgia, and are cold hardy in zones 5-8. One particular species of flame azalea is Rhododendron calendulaceum, and was first noticed in American forests in 1765 by the great botanists and explorers John Bartram and his son, William Bartram, author of the classic book, Travels. The Bartram family members were English loyalists to the English King George III during the American Revolutionary period. English noble plant collectors who were searching to buy interesting plant specimens, roots, and seed of unique American native plants sponsored and financed the expeditions of the Bartram family. John Bartram was appointed by King George III as the official royal botanist to the American English colonies. Even though William Bartram sent specimens of the flame azaleas back to England after he wrote extensively about them in his botanical classic, Travels in 1773, he was not given credit for the present naming of the flame azalea, which he called the “Fiery Azalea.” It was the French botanist Andre Michaux, sent to the colonies in 1795 to collect plants for France, who received credit for the name “Flame Azalea,” Rhododendron calendulaceum, for this particular American spectacular flowering azalea instead of William Bartram, who actually had seen and identified several species that he called “Fiery Azalea,” twenty-two years earlier than Michaux. Bartram described the Flame (Fiery Azalea) with a glowing spectrum of colors of orange, finest red lead, yellow, bright gold, and cream. All of these colors were observed to appear on a single plant by William Bartram. In his book, Travels, William Bartram observed that giant clusters of flowers covered the azalea bushes with incredible profusion along the sides of the hills. Bartram was affected with a mystical apprehension that the hills were “set on fire” (page 321), and he described the “Fiery Azalea” as the “most brilliant flowering shrub,” known up to that date—no plant or shrub exhibiting such a great “show of splendor.”

Native flame azaleas can grow 10 feet tall and 15 feet wide and can be grown into a flowering tree as a specimen in the landscape garden. The size of most other flowering landscape azalea bushes is quite variable, some dwarf azaleas grow one foot tall and others up to 15 feet with age. Some azaleas in Japan are reported to be several hundred years old and grow into small trees with trunks up to one foot in diameter.

Most gardeners prefer to buy azalea shrubs at a nursery in the spring while the bush blooms. Some azalea experts suggest planting azalea shrubs in the winter or fall by buying containerized nursery bushes, so that the root system can support beautiful flowering in the spring. Most azalea shrubs are slow growing in the landscape, and many gardeners prefer to buy large established azalea clumps that will flower on a grandiose scale in the spring.

Azalea bushes thrive under the partial, filtered shade of pine trees, along with companion dogwood trees and camellia shrubs. Azalea plants are better grown in partial shade, and when planted next to buildings, the north side offers protection from cold damage. The flowers of the azalea plant last longer in filtered pine tree shade because of the cooling effect. Pine tree straw, pine cones, and pine tree bark make excellent mulch under azalea bushes by conserving soil moisture and preventing weeds. When planting azalea bushes, the shrub should be put into a landscaped hole that contains half soil and half organic matter, such as pine tree bark or peat moss. Azalea plants are very shallow rooted and must be grown in an organic soil mixture.

The azalea plant is acid loving, and a pH of 4.5 to 5.5 is ideal for vigorous growing. Watering may be necessary if rain does not happen for a two week period and fertilizing is usually avoided. Fertilizer can burn the tender fibrous root system. If yellowing occurs in the leaves or leaf veins, Iron or Magnesium (Epsom salts) will usually correct the condition. Leaves and humus are the best organic fertilizers for azaleas and generally fertilizer is not recommended, because the plant may be damaged or killed by gardeners who wish to be “too kind” to their plants. Azaleas flourish in an acid soil (low pH), and lime should never be used, since it can be fatal to your azalea plants.

If leaves of azalea shrubs show a dull, dark green leaf color with reddening beneath, this means that there are deficiencies of phosphorus in the soil that can easily be corrected by applying phosphorous in water-soluble fertilizer, such as miracle grow. Bright green, shiny azalea leaves generally means that the azalea plant is in a healthy state of growth.

If azalea bushes are pruned after flowering, during the summer, there may be only few azalea flowers formed the following season, therefore the sooner you prune after flowering, the better your chances are of ensuring beautiful flowering next year.

Azalea shrubs are easily propagated and increased by taking a cutting about 8 inches long and placing the cut end about 2 inches deep in sand. Roots on azalea plants can form within a week during June and July, and the plant may grow another foot tall before it is ready to be planted permanently in your yard.

There are thousands of different cultivars of azaleas. An excellent reference book, Azaleas, by Fred Galle, describes 6000 flowering varieties, and is published by Timber Press. Very few of these azalea cultivars are available commercially, because most nursery garden centers do not wish to stock shrub perennials, unless they are in bloom, and the blooming period of azalea is restricted to a month or less. Azalea plants don’t sell well unless they are in full flower – except from year round shipping by internet companies that can ship them at any season.