7 Care Tips for Indoor Azaleas
Indoor azaleas bloom at right in time with the holidays. They bring color to winter days with bright blooms in red, white, pink, salmon, and purple. Florist selections this time of year make sweet gifts loaded with buds and lush evergreen foliage in small, giftable pots.
These florist azaleas usually represent two cultivated species and their hybrids in the large Rhododendron genus: R. simsii and R. obtusum. Formosa and Hiryu azaleas, respectively, naturally grow in China and Japan as understory shrubs in mild-climate woodlands with rich, acidic soils. Forced to bloom in winter with controlled temperatures and growth, a spring and early summer bloom time is the usual cycle.
Most are R. simsii, an evergreen shrub in USDA zones 8-10. Formosas enjoy summer outdoors in pots, overwintering inside in cold climates. Rhododendron obtusum can move out to the garden in spring. With shelter from winter winds and mulch protection, it survives outdoors in USDA zones 7-10.
To enjoy your indoor azalea to its fullest, we’ll cover the essential seasonal care tips. We’ll also look at keeping it beyond the season for those not ready to part with the bloomer.
Cool Temperatures
Cool temperatures are important for the best and longest-lasting indoor azalea blooms. Ideal daytime temperatures are between 60-68°F (16-20°C), with nighttime temperatures near 50-55°F (10-13°C). Warmer temperatures—75°F (24°C) or higher—indicate a warming spell, and buds and flowers may drop as roots warm. Below 50°F (10°C), too, risks slow development and bud loss.
A cool environment helps the petals hold longer. Place pots in a cool room or near a window to experience lower temperatures. In warm situations, they’ll open and drop more quickly.
Indoor specimens perform best in cooler temperatures, but chilly blasts or prolonged cold exposure cause leaf and stem damage. Temperatures near 40°F (4°C) result in bud loss, while near-freezing conditions can damage tissues. Alternatively, hot and dry conditions cause stress and deterioration.
Humidity
Humidity is an important care consideration for overwintering indoor azaleas. A level of around 50% or higher is best, and while this is average in many households, winter can vary with heated conditions.
Keep pots out of drafts to avoid drying air, hot or cold blasts, and drastic changes. Heating and air vents, open doors, space heaters, and fireplaces cause sweeping fluctuations that may inhibit blooming.
To increase humidity, group houseplants to raise immediate air moisture. Or, place the container on a tray of pebbles filled with water. The pot should rest on the pebbles, not in the water, to avoid oversaturated soils.
Keep Soils Moist
Florist azaleas come with a couple of special watering needs. The first is that they are often in a peat moss potting media. When peat dries, it takes time to rehydrate. Azaleas have fine surface roots that are sensitive to drying out, and you’ll notice quick wilting. It’s best to keep soils evenly moist and well-draining without drying between sessions. When the soil surface is dry on top and half an inch deep, it’s time to water.
The second note is their sensitivity to lime in hard water. Tap water in hard water systems may contain alkalinity in the form of dissolved sodium bicarbonate, which is toxic to azaleas. If you have hard water, rainwater or bottled water is best.
How to Water
If your specimen is in a peat-based mix with significant drying, rehydrate it with a good soak. Submerge the pot in a sink or bucket of tepid water for 15 minutes. Let it drain thoroughly post-soak. Continue with a regimen for even moisture, watering when the media begins to dry on the surface.
Watering frequency is usually about once a week, depending on the growing environment. Water deeply until it runs through the pot’s drainage holes. Don’t leave a filled tray to linger beneath the container long after a watering session.
Optimal Light
Indoor azaleas thrive in bright, indirect light. Place them near an east-facing window or, in cold climates, a south-facing winter exposure. Four to six hours of indirect sunlight sustains the energy needed to flower.
Keep the pots out of direct sunlight to prevent burning the tender leaves and petals. Filter direct rays with a curtain for dappled light.
Post-Bloom Care
Florist azaleas delight for a season. Growers prune roots and control upper growth so they’ll fit beautifully into our homes as potted specimens in full flower. If you want to try growing them year-round, a combination of indoor and outdoor growing is helpful.
They’ll do best outdoors where hardy and overwinter indoors in colder climates. It can be challenging to get them rebloom indoors, and it may take a year or two after forced conditions.
Deadhead
Remove faded blooms from potted selections to direct energy into developing strong roots and healthy foliage instead of producing seeds. Deadheading the large trumpets also improves air circulation in the dense crown. Dropped blooms foster damp conditions that may promote disease as they lay in place on healthy leaves, stems, and the soil surface. Removal also helps tidy the look.
Repot
Potted azaleas benefit from repotting every two or three years. When it’s time to repot, you may see roots poking through drainage holes or popping up on the surface. Stems may wilt, and soil will dry out quickly.
A primary reason to repot is to refresh soil nutrition and aeration. Potting mixes break down with regular water and root development. Nutrient and oxygenation levels necessary for health lessen.
The best time to repot is right after flowering. Transplanting at other times can affect foliar growth and budding. A commercial potting mix specifically for acid-loving plants is a great option. Otherwise, use a high-quality mix amended with pine bark chips and horticultural sand.
In the ground, they benefit from acidic soils. The sweet spot is a pH between 4.5 and 6.0.
The Right Fertilizer
Acid-loving azaleas are sensitive to increased alkalinity, which can cause iron deficiency. Certain potting materials, hard tap water, or overfertilizing can cause toxicity. Alkaline soils have high pH levels (above 7.5). Adjusting soil pH makes iron available.
Alkaline soils block access to nutrients, leading to yellowing leaves, a lack of vigor, and eventual decline. Organically rich soils with good drainage (including pine bark chips or horticultural sand) are a good foundation.
Avoid overfeeding potted specimens. If you’ve just received the beauty in bloom, it won’t need fertilizer until spring, if at all. If you’re nursing an existing azalea, stick with a formula for acid-loving plants (rhododendrons, hollies, camellias). A tailored acidic formula provides nitrogen in the beneficial form of ammonium nitrate over common nitrate nitrogen. Garden sulfur and iron chelates are other amendments to correct deficiencies.
If you keep your azalea, begin fertilizing in early spring as new growth emerges with a granular or liquid feed. Granules need to be reapplied every two to three months, while liquids absorb quickly and require more frequent application. Apply it every other watering session in the warmer months.
Pests and Diseases
Fortunately, indoor azaleas have few pest and disease problems. Spider mites may visit, and root rot from overwatering can occur. Fortunately, these issues are preventable.
Spider Mites
Spider mites are common in houseplants and live on the undersides of leaves, indicated by webbing and light yellowing of leaf surfaces. Outdoors, beneficial predatory insects like ladybugs and predatory mites help control populations.
These pesky pests gravitate toward specimens stressed by under or overwatering. For small populations, run plants under a stream of water to displace the pests. Dab them with a Q-tip or cotton swap soaked in isopropyl alcohol. Insecticidal soaps and horticultural oils are effective as more potent treatments.
Root Rot
Overly soggy soils damage roots and lead to their inability to uptake water and nutrients necessary for flowering. A common fungal disease to look out for is root rot. Overwatering creates saturated conditions that promote its development. Rot causes the roots to turn brown and mushy and as they decay, they can’t function to support growth.
Plants in overly soggy media with poor airflow may show yellowing and wilting leaves. Slip plants out of their pots to check the roots and clip off those that are brown or damaged. Replant the azalea in fresh media and water thoroughly. If caught early, you may see rebounding growth.
