Azaleas, popular shrubs with brightly colored flowers, are a star attraction of many gardens, especially in the Southern U.S. A member of the genus Rhododendron, there are over 6,000 varieties of azaleas, in many colors, from coral to pink, purple and white. Gardeners can choose from many hybrids, in different sizes, to decorate their indoor or outdoor space.
Growing the Azalea
Azalea shrubs thrive in partially shaded environments and need acidic, well-drained soil to stay healthy. Some species of this slow-growing plant need regular pruning, but others require trimming mostly for propagation or shaping.
What You Should Know About the Azalea
When planting this shrub, choose an appropriate planting location in your garden. The flowers look best when planted alone, but placing them against a background of conifers will show off their colors without overpowering the other foliage in your garden.
Plant azaleas in well-drained, but moist soil, with a slightly acidic pH of 4.5 to 6.0. Use loam soil, (a mixture of soil, clay, silt and sand) that allows rapid drainage of water. The soil should contain plenty of organic matter (even chopped leaves and ground bark will work).
In gardens with heavy soil that tends to hold water, place the flowers in a raised bed to prevent damage. Place plants on top of the ground or an inch above the ground, and pack acidic soil around the root ball.
Use mulch, including decomposing leaf and wood mould, pine needles and wood chips, to even out the soil temperature and add much-needed humus. If azaleas are properly mulched, there’s no need for fertilizing. If you want to use a fertilizer, or if leaves are drooping or growing in smaller than normal, use a balanced fertilizer containing equal parts nitrogen, phosphorus and potassium. Spread compost lightly over the entire root area, which can go up to a radius of nine feet. Fertilize in March, May and July if needed only if the soil proves to be nutrient-deficient.
Light and Water Needs
Keep indoor azaleas evenly moist, and mist the leaves to increase humidity. If the plant becomes too dry, it may attract spider mites. Outdoor plants need about an inch of rainfall each week. If you live in an arid region, give the plant a thorough watering every week, but make sure all water drains through the pot or planting area.
The shrubs thrive with a combination of direct sun in the early morning and some shade in the afternoon, or intermittent sun all day. The variable shade provided by tall trees swaying in the breeze offers the perfect combination of sun and shade for azaleas.
Azaleas adapt to different lighting, depending on geographic location. In the northern U.S., they can survive in full sun but will suffer under hot, direct sunlight in the muggy Southern states. The shade of the North may damage the plants, whereas even shady conditions in the South allow the plants to thrive. These hardy shrubs can survive temperatures of up to 86 degrees with no problem. Ideal temperatures depend on the variety of the azalea shrub, but most outdoor plants grow well in 60 to 70-degree weather.
Choose greenhouse azaleas, not the hardy variety, to grow indoors. Keep indoor plants at 60 to 65 degrees, and place them in indirect sunlight. Water regularly, and keep soil even and slightly moist. Don’t fertilise your indoor plant unless it has flowered.
Learn more about how to grow azaleas indoors on “How to Care for Indoor Azaleas Year Round” from the GardenCenterTV YouTube Video Channel.
Planting and Propagating
Prune small branches when your plant’s bloom has peaked, and use them to propagate azaleas for indoors.
Grow new azaleas from these pruned stems, and propagate plants late in spring when leaves have matured. Examine the parent plant to make sure it’s disease and pest-free, and water two days before cutting. Snip stems cuttings from the ends of branches. Put the cuttings in a plastic food storage bag and place in an ice cooler or refrigerator for a day or two, if you’re not able to root the cuttings right away,
Prepare the stems by removing all leaves and flower buds. For faster rooting, scrape off bark on the lower inch of stem. Put the cutting in a loam soil mixture, and keep humidity high to encourage growth. You can use a wire frame, clear plastic bag or part of a plastic soda bottle to make a propagation dome and retain humidity until the cuttings root.
Prune an azalea bush, so it has a natural look. If you prune it into a boxy shape, it will cause sparse growth of flowers and branches. Use pruning shears and cut single branches instead. When pruning your shrub to make it look more attractive, pick out branches that interfere with your mental picture of the result. Trim extra branches one at a time. Avoid cutting more than a third of any branch.
Revitalise a sparse plant by cutting three to five of the branches by a third and prune all the other branches according to the shaping instructions. You don’t need to worry about cutting a connecting branch during pruning. Branches grow back from below the cutting point.
Potting and Repotting
Find a pot with adequate drainage and add a screen to the bottom to prevent the substrate from escaping. For one cutting, use a container that’s 8 inches in diameter. Fill the pot with a 50/50 peat moss and perlite mixture. Put rooting hormone on a three to six-inch cutting and stick the bottom inch or two into the potting medium.
Move a plant from one pot to another by gently scooping the roots out with a trowel, and plant the root ball in new soil up to the same depth as the old pot. Make sure there’s enough soil packed firmly around the top of the pot to support the plant.
Water cuttings until moisture drops from the bottom of the container. Set in bright but diffused sunlight in 65 to 75-degree temperature. If the cutting hasn’t rooted, place a plastic bag over it to retain moisture until it roots.
Watch a first-hand tutorial on “How to Grow Azaleas from Cuttings” on the World Clik YouTube Video Channel.
Problems and Precautions
Azaleas offer a beautiful focus to any garden, but they’re poisonous to pets and humans if ingested. All parts of the plant, even the honey, contain grayanotoxins, which cause vomiting, irregular heart rhythms and other dangerous symptoms. Keep azaleas in an area where dogs, cats, horses and small children can’t get to them.
The plant’s soil lacks nutrients when leaves show a yellow color between the veins. Treat this condition with a slow-release fertilizer containing iron and sulfur. Apply it after plants bloom and again in mid-summer.