plant of the month
Rhododendron spp. (ro-do-DEN-dron)
Azalea, Florist azalea
Azaleas have funnel-shaped flowers in clustered heads. Single-, semidouble- and double-flowered varieties are available as are ruffle-petaled varieties. Leaves are dark green, leathery and oblong to obovate shaped. Houseplants are typically dwarf shrubs that grow to heights of 1 foot to 1.5 feet, but “topiary” forms also are cultivated today.
Hues include a range of reds and pinks, lavenders and purples, peach, salmon, coral and white as well as bicolors.
With proper care, azaleas typically provide consumers two to four weeks of flowering enjoyment, depending on the plants’ stage of maturity at the time of purchase (see “Purchasing Advice,” below). Blooming is often followed by a flush of new foliage.
Azaleas are available year-round.
in-store and consumer care
Azaleas require bright diffused light (no direct sunlight).
These plants’ potting medium, which is usually all or part peat or Sphagnum moss, dries out quickly and must be kept evenly moist at all times. Water with soft water, if possible. If the potting medium dries out, it can be difficult to rehydrate and usually requires submerging pots into a larger container of water for an hour or so several times each week; even then, irreversible damage to the plant may have occurred.
Azaleas prefer cool air; 60 F to 70 F during the daytime and 50 F to 60 F at night is ideal.
Azaleas like high humidity levels. Misting leaves daily during the blooming period can be helpful in dry environments.
While blooming as houseplants, azaleas require no fertilization.
Azaleas prefer a potting medium of equal parts peat or Sphagnum moss and soil.
Azaleas are affected by exposure to ethylene gas. Symptoms include bud, flower and/or leaf drop.
Remove faded flowers promptly.
Unless you live where winters are short and mild, florist azaleas are difficult to get to rebloom (unlike the hardy garden Rhododendrons/azaleas). It’s usually best to advise customers to enjoy their azalea plants as they would long-lasting cut-flower arrangements.
BUD, BLOOM AND/OR LEAF DROP
Causes include exposure to ethylene gas, dry potting medium (see “Shriveling Leaves,” below), low humidity, high temperatures and exposure to direct sunlight.
The most common cause is dry potting medium. Soak the pot in a larger container of soft water for at least one hour, until the potting medium is thoroughly saturated (bubbles disappear), several times each week. Other causes are low humidity, high temperatures and exposure to direct sunlight. If the plant loses more than one-third of its leaves, discard it because it will never recover.
This is an indication of either an iron deficiency or the presence of lime in the potting medium or water. To treat an iron deficiency, fertilize the plant with an acid azalea food that contains iron. To rid compost of lime, treat with Multi-Tonic, and water the plant with soft water.
This can be due to root rot caused by fungi in the soil. Infected plants should be discarded.
Spider mites are the most common azalea pests, and infestations occur when the air is too warm and/or too dry. Parched or crinkled leaf tips, with webbing on leaf undersides, is a sign of spider mites. Prune infested stems, and spray remaining plant parts with insecticidal soap; however, if more than one third of the plant is infested, discard it.
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WHAT’S IN A NAME The genus name “Rhododendron” is derived from the Greek rhodon (rose) and dendron (tree).
FAMILY MATTERS Rhododendron is a member of the Ericaceae (heath) family. Relatives include Erica (heath), Calluna (heather), Gaultheria (salal), Vaccinium (huckleberry/blueberry/cranberry) and manzanita.
HOME SWEET HOME Azaleas are native to Japan; Southeast Asia, from the Himalayas and southern China south to Malaysia; and the temperate regions of North America.
Buy plants that have masses of well-developed buds and no more than 20 percent open blooms.
Photos: Bay City Flower Company, Inc.
Some information provided by:
by Terrill A. Nell, Ph.D., and Michael S. Reid, Ph.D.
Botanica, by R.J. Turner Jr. and Ernie Wasson
Chain of Life Network® , www.chainoflife.org
Complete Guide to Conservatory Plants, The
by Ann Bonar
Complete Houseplant Survival Manual, The
by Barbara Pleasant
by Liberty Hyde Bailey and Ethel Zoe Bailey
Houseplant Encyclopedia, The
by Ingrid Jantra and Ursula Krüger
House Plant Expert, The, by Dr. D.G. Hessayon
SAF Flower & Plant Care