Question: Over the last few years, I’ve bought 3 different indoor azaleas and they all died within a month of purchase. I love this plant and want to try again. What can I do to keep it alive?
Answer: The indoor or florist’s azalea (Rhododendron simsii) is certainly not the easiest houseplant to grow. Many people lose theirs quite quickly, yet, if properly tended, it can not only live for years in the average home, but go on to bloom year after year.
The main difficulty with the indoor azalea is that it is generally sold seriously underpotted. Whether this is for aesthetic reasons or to save space in the production greenhouse, I don’t know, yet when you bring it home, you’ll discover it starts to wilt after just a few days. With massive quantities of fine roots crammed into a small pot, a once-a-week watering schedule just isn’t going to suffice!
Try giving it a soak—immersing the whole root ball in tepid water for 10 to 30 minutes—once every 3 to 4 days. Watering once a week will only be sufficient if you’re able to grow it under very cool conditions (45–60°F/7–16°C). Soaking the plant more than once a week should keep it alive and well during its initial flowering … and that can last 6 weeks and more.
The gardening industry considers the indoor azalea to be a temporary houseplant: just a gift item you’re supposed to toss it after it finishes blooming. However, it will actually live for decades indoors and rebloom annually if you know what to do. True enough, this is not a plant for beginners, but if you like a bit of a challenge…
So, as soon as you get the chance, why not fix that “needs watering twice a week” thing? It was sold to you underpotted, so move it into a pot of a more appropriate size, probably two pot sizes larger than the original (i.e. if the plant was in a 6-inch [15 cm] pot, move it to a 10-inch [25 cm] pot). Since soil is a natural water reservoir, more soil around its roots means the plant can now go longer between waterings.
The azalea prefers acid soils, with a pH of about 4.5 to 5.5, although 6 is acceptable. The average potting mix, with a pH of 5.5 to 6.5, is just a touch too alkaline. So, dilute its alkalinity by mixing in one third peat moss, a naturally acid sol ingredient: that will bring the pH to just the right level.
Although an indoor azalea bought in flower will “hold” in weak light, for healthy new growth and future flowers, it will need more: bright light much of the day including a few hours of direct sun, especially cool morning sun. In winter, full sun is not too much, especially in higher latitudes.
One thing that won’t change is that you’ll have to keep the growing mix moist at all times. An azalea simply will not stand drying out and every time you let it wilt brings it one step closer to the grave. Check regularly and water as needed.
Ideally, you’d water with lime-free water. Tap water is usually alkaline, so rain water or distilled water (or water from your dehumidifier) would be best, but… I find you can get away with tap water from fall through spring as long as you do one thing: put your azalea outdoors for the summer where rains will flush the soil of any alkalinity.
A summer outdoors in a partially shady spot is practically a sine qua non for this plant anyway. It seems to please the azalea in more ways than just water quality.
Fertilize during the growing season (spring through early fall). Again, if you can find a fertilizer designed for acid-loving plants, all the better.
Leave your azalea outdoors well into fall, bringing it indoors only when frost threatens. This will give it the cool conditions necessary for initiating flower bud formation: 40 to 55°F (4 to 13°C). If you’d done your job well, it will already be full of flower buds before you bring it in.
Indoors, keep the air humidity up or the flower buds could dry up. You could use a humidifier or place the plant on a humidity tray (pebble tray). Room temperatures are acceptable once flower buds have been initiated, but still, your azalea prefers cooler conditions than most other houseplants. Night temperatures of 45–60°F (7–16°C) will make it especially happy.
In general, homegrown azaleas bloom less densely than greenhouse-grown ones, but do so over a longer period, often from late fall right through until spring.
Do keep an eye out for pests. Spider mites are a threat in dry air, while mealybugs and scale insects can travel to your azalea from infested plants nearby.
As for multiplying your plant, now you’re really pushing your luck, but stem cuttings taken in spring, dipped in rooting hormone and kept under high humidity, like under a transparent dome, will root … eventually. Don’t be surprised if the success rate is low and if even the few survivors take up to 3 months to show signs of growth!
There you go: you really can make your indoor azalea thrive and even rebloom indoors. It just takes a lot of TLC!