Azalea are popular garden and landscape plants that are prized for their foliage and beautiful flowers. Hundreds of varieties have been developed by breeders and horticulturists over the years, and today, these woody shrubs, members of the Rhododendron genus, are often grown in containers. Growing azalea in pots is very easy, as these plants adapt well to container gardening. They are also popular with bonsai enthusiasts, who grow azalea that are no more than a hand's breadth in size, providing a good example of their ability to thrive when grown in containers, even when very small. Growing azalea in pots is a simple matter of providing the proper sun, soil, and water conditions.
The best soil mix for azalea depends on several factors. Azalea like soil that is slightly acidic, well drained, and rich in organic matter. Many nurseries and large garden centers sell soil mixes specially formulated for azalea in pots. If special azalea soil is unavailable, use basic potting soil and adjust for pH with a suitable soil additive to bring the soil into a range between pH 5.5 and pH 6.0, which is slightly acidic. Additives for adjusting soil pH are available at any garden center.
Before planting, make sure the pots have ample drainage. There must be holes in the bottom to allow excess water to drain away. Fill the bottom of the pot with a layer of pebbles, lava rock or even broken terra cotta or pottery shards about 2 inches deep. Then fill the new pot with enough soil so that when you add the azalea plant, the top of the root ball will be 1 to 2 inches below the rim.
Next, remove the azalea from its temporary garden center pot, and while supporting it, add soil around the plant, very gently packing the soil as you fill the pot, using care not to compact the soil. The aim should be to firm the soil slightly without compressing it. Fill to the where the root ball joins the stem. Moisten the soil and place the plant in a spot that gets lots of light, especially morning sun, and that is at least partially shaded during the hottest parts of the day. Azalea plants dislike too much direct sun, particularly in warm climates.
Water azalea regularly. Use your finger to check the soil, and when it is dry to a depth of a finger length or so, water until water runs from the holes in the bottom of the pot. Wait a few minutes and repeat. Fertilize the plant using a general purpose fertilizer for container plants or one of many specialty fertilizers for azaleas and other acid loving plants. Follow the manufacturers directions for whatever fertilizer you choose. Generally, fertilizer should be applied every two weeks during periods of growth and discontinued near the end of growing seasons and during dormant periods.
In areas with mild winters, where temperatures rarely drop below freezing, the azalea may be kept outside year round if given protection from sun and cold winds. In areas with harsher winters, azalea in pots should be brought inside and placed in a bright, sunny window. The plant can be returned to the outdoors in the spring when danger of hard freezes or temperatures below 30 degrees F (-1.1 degrees C) are past.