Ever Green

By Lois Taylor

Friday, May 21, 1999

By Craig T. Kojima, Star-Bulletin
Azaleas are ill-suited to the hard-packed,
non-acid potting medium most nurseries use.

Getting azaleas to thrive

IF that beautiful potted azalea you got for Mother's Day is fading fast, it could be for a couple of reasons.

One is that most azaleas have been planted in compacted soil that is not strongly acid, and the other is it hasn't had enough water.

Azaleas are part of the rhododendron family, a clan that will not tolerate too much lime in the soil. The planting material provided by nurseries often compacts easily and because rhododendrons and heather are almost the only commercially potted plants that need acid soil, they may be have been planted in a general potting mix.

Azaleas have a mass of fine fibrous roots that should form a solid rootball, and this happens best in a very loose soil mixed with peat moss or chopped fern bark.

They need more air in the root zone than any other garden plant, but at the same time, they need a constant supply of moisture. That means they need a planting medium that drains rapidly but retains moisture, and that's the purpose of the fern bark or the peat moss. Poor drainage results in root rot, which causes yellowing leaves and wilting flowers.

Azaleas grown in pots dry out quickly, especially during warm weather, so they need frequent but light watering. Serious growers on the mainland collect rain water to irrigate their plants, but our tap water is relatively free of salts.


Bullet Replant in loose soil with peat moss or chopped fern bark
Bullet Water lightly but often, especially on warm days

When potted, azaleas should be grown in small, shallow containers since they have shallow roots. There must be plenty of good drainage holes in the bottom of the pot, and growers often suggest an inch of pebbles or broken pottery at the bottom.

When grown outdoors, azaleas bloom best in sunny or partly shady locations and in cooler parts of the island. In hot, dry areas such as the Ewa plain and from Kaimuki to Hawaii Kai, they do best in partial shade with only morning sun.

The most popular azalea grown here, Rhododendron indicum, is a native of Japan, where it is called Satsuki-tsutsuji. It has an interesting history. In 1639, the Japanese officially broke off all trade with foreigners except for the Chinese and the Dutch. Unconsciously a master business move, this self-imposed isolation created a huge interest in Europe in anything Japanese. Azaleas began to appear in China, and were then taken to Europe by plant collectors, where like your Mother's Day plant, they collapsed.

Growers slowly learned the secrets of soil and water, and they became wildly popular as a greenhouse plant in the manor houses of England and France.

During World War I when Holland remained neutral, a grower named F.M. Koster imported the Hinodegirl variety of azalea from Japan and hybridized it with a hardier European variety. It was an immediate success, and Koster decided to extend his profits by moving to the United States.

The nursery he founded in New Jersey in 1921 was the source of much of the azalea stock of the plants we grow today.

At the same time in Japan, Motozo Sakamoto was raising seedlings of wild azaleas found on Mount Kirishima. His collection was taken over at his death by another horticulturist, Kojiro Akoshi, who displayed 12 of his plants at the Panama Pacific Exposition in San Francisco in 1915. They were a sensation, and launched the career of California nurseryman Toichi Domoto who imported the plants from Japan.

Azaleas have since been hybridized all over the country, and have been easily available to gardeners for the last 50 years. Here, azaleas are frequently used as bonsai material because of their small leaves and flowers or planted outdoors as single plants or massed in borders. They are also a beautiful accent to the traditional Japanese rock garden.

Azaleas in the garden should be fertilized at the time they come into flower, using a commercial acid fertilizer designed for rhododendrons. Growers often recommend using half as much twice as often as directed on the container. Potted azaleas should be fertilized monthly, and watered immediately and thoroughly afterward.

They will accept fairly drastic pruning, which is another reason they are a favorite for bonsai growers. They should be pruned just as the flowers are finished. If the terminal buds, found in the center of a rosette of leaves, are pinched, side buds and branches should form. Removing dead flowers at their base, just above the new buds, will produce a heavier flowering.

Azaleas are not particularly prone to pests, but thrips and spider mites will discolor the foliage. Diazanon or malathion will get rid of the thrips and sulfur solution will discourage the mites.

The latest development on the mainland by azalea breeders is a low-growing dense plant used as a ground cover. Much of the year it will present a deep green mass, but in the late spring it will bloom in a glorious burst of cover. But, remember, only in an acid soil.

Do It Electric!

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