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Why is my indoor azalea dropping buds and leaves?
Only a couple of species of the large genus Rhododendron which includes azaleas have been developed extensively as houseplants. These are known as "florist azaleas". Many people regard these beautiful indoor plants as being "difficult" because they tend to shed leaves, buds, and flowers when subjected to unfavorable conditions. This need not be so, but keep in mind that azaleas flourish naturally under conditions that are nearly opposite from those encountered in our usual indoor environments. Of the various symptoms of distress, bud drop is probably the most aggravating to the average indoor gardener. It can be minimized by taking some simple precautions.
Azalea bud drop can result from any of a number of factors; moving the plant, chilling, high temperatures coupled with low humidity, low soil moisture, and/or insufficient light.
Often the transfer of a plant from grower to home involves two moves, both of which may be resented by your azalea and can contribute to bud drop. When moving your new plant from florist to home, take special precautions to avoid chilling during winter weather. If the plant is in bud and flower, put it in a cool, bright, but not sunny, spot in your house and leave it there until flowering is over.
Although azaleas grow best under cooler temperatures, they can be damaged by severe chilling. Exposure to temperatures below about 40 degrees can cause buds and flowers to fall. Leaves can also be affected at temperatures near freezing. In addition to taking precautions during moving, you should also avoid drafty window sites and unheated growing spaces during winter months.
Azaleas thrive when kept in sites where the temperatures range from 50 to 68 degrees. If they are suddenly moved into warmer rooms, (75 degrees and above), soils will dry quickly leading to bud and leaf drop. If warm temperatures are coupled with low humidity, expect increased needs for water and short-lived flowers.
Most florist azaleas are potted in nearly pure peat moss which should be maintained in an evenly moist condition. If such potting media are allowed to dry excessively, rapid wilting and fall of flowers, buds, and leaves can be expected. Additionally, such potting soils are difficult to re-wet satisfactorily. Immersion of the pot in a container of tepid water for about 15 minutes, followed by thorough draining, is a good method for moistening a dried-out soil ball. Azaleas also prefer medium to high humidity. Humidity-wise, dry growing conditions can be improved by using wet pebble trays as pot supports and by regular misting of your plants. To maintain their health, however, avoid soggy soil conditions, and never allow your plants to stand in puddles of water. In the St. Louis area, azaleas should be watered with rainwater, or with tap water containing one tablespoon of vinegar per gallon.
Potted azaleas in bud or bloom should be placed in a cool, bright site but not in direct sunlight. Avoid drafts of hot, dry air and cold blasts of air from nearby doors or windows.
Most florist azaleas are discarded when they have finished flowering. However, Rhododendron obtusum hybrids are relatively hardy and can be planted permanently in protected, outdoor sites about May 1. They will require mulching for winter protection. Rhododendron simsii hybrids must be returned indoors to survive through subsequent winters. Both species are somewhat difficult to rebloom indoors.