Growing Guide for Azaleas: Plant Care Tips, Varieties, and More

Azaleas are a distinctive part of landscapes all around the world. There are varieties that are native to North America, Europe, and Asia. They make great border plants that can flower in early spring when few other shrubs do. Often they are used on banks and around foundations or steps, where they serve as deep green backdrops to shorter perennials and annuals blooming later in the season.

Botanical Name	Rhododendron
Common Name	Azaleas
Plant Type	Deciduous or evergreen flowering shrub
Mature Size	Typically between 3-10 feet; can grow up to 20 feet
Sun Exposure	Filtered sunlight
Soil Type	Nutrient-rich. acidic
Soil pH	5.0-5.5
Flower Color	White, pink, orange, red
Toxicity	Toxic to pets

How to Plant Azaleas

Most people propagate their azaleas or purchase them from a garden center, but it's not difficult to grow azaleas from seed. Azaleas can grow from a few feet tall (for dwarf varieties) to up to 20 feet. Plant them in a protected area away from prevailing winds. Early spring is the best time for planting, especially in northern climates, so that the plants have time to establish strong root systems before winter sets in.

Azaleas prefer well-drained soil. Before you plant your azalea, dig a hole and fill it with water. If the water does not drain readily, then double the size of the hole and fill it half-way with a mix of sand and compost, which will increase the soil's drainage.

Growing From Seed

Growing azaleas from seed is the least expensive route to these beautiful plants, but patience is required, as it may take three to four years until you see blooms. 

Start with any dry flower pot about the size of a gallon milk jug. Make sure you have washed it with soapy water and that it has holes in the bottom for drainage. Fill the pot halfway with a potting mix and moisten it with distilled water (to avoid impurities and chlorine). Add a top layer of sphagnum moss, then spread a few well-spaced seeds over the moss. Add an azalea fertilizer, then seal the flower pot with plastic wrap or a plastic bag to create humidity.

Place the pot about 4 inches below a regular lamp for 18 to 24 hours a day. Germination will take 2-3 weeks. Once they've developed a second set of leaves, you can divide the plants into separate cells or small pots. Keep them moist and under lights until they develop 4 or 5 sets of leaves, at which point you can gradually acclimatize them to their final setting. Plant them once all danger of frost has passed.

Growing From a Starter

You can propagate your own azaleas by dividing existing plants. Simply dig up a plant, break the clump of stems and roots into segments, then replant them. It sounds brutal, but you'll be restoring vigor to older plants, as long as each segment contains healthy stems and a mass of roots. Trim off any old or dead roots and stems, and cut off about a third of the top growth, since the remaining rootstock will only be able to support a smaller plant. Divide plants when they are dormant, either early spring or late fall. Dig your new holes in advance so that the roots are exposed to air as briefly as possible so that they don't dry out. Carry the segments by the roots, not by the stems. 

Layering is another method of propagation. This involves burying a low-lying branch without detaching it from a healthy plant and turning it into a root. Early in spring, strip a single stem of all but its topmost foliage. Scar the bark in the stripped portion of the stem and apply a hormone (available at garden centers) to spur root growth. Bend the stem to the ground and bury it up to its tip in a shallow trench. Keep the soil moist.

By the beginning of the following spring, you will have a well-rooted plant ready for cutting from its parent. Apply a liquid organic fertilizer, then leave the cutting in its place for a few weeks before transplanting. 

Azalea Care

Once established, azaleas need little care except for the occasional watering during dry periods. Native azaleas are better at tolerating drought and, being natives, are hardier in North America and easier to grow. Just be sure to grow azaleas that are suited for your climate.

Slow-growing, azaleas need little help from mulch, but if you must mulch for aesthetic reasons, a thin layer of light-textured mulch or pine bark will do. Don't over-mulch. Azaleas have rather shallow roots, and over-mulching them smothers them with love.  

Light

Azaleas can tolerate more sun exposure than rhododendrons, but contrary to popular belief, neither are full-shade plants. Filtered sunlight is best, as long as they receive some direct sun. In northern climates, azaleas will do well in four to six hours of full sun. In southern climates, limit exposure to direct sun to no more than four hours.

Soil and Nutrients

Azaleas prefer growing in nutrient-rich, acidic soil with a pH balance of 5.0 to 5.5. If your soil needs amending, you can add sulfur or iron sulfate to increase the acidity. To maintain acidity, provide an annual application of an organic fertilizer designed for acid-loving plants. Alternatively, pine needles or shredded oak leaves make an excellent mulch, as they slowly add acid to the soil. Wait until after the flowers bloom in spring to feed your azaleas. This delays new growth and prevents it from being damaged by a late frost.

Water

Standing or excess water leaves azaleas susceptible to molds and fungi, so make sure your soil drains well. An inch of rain per week during the growing season is ideal. If you need to resort to hand watering, avoid wetting the leaves in order to discourage molds.

Overwintering

If you live in a cold climate, protect your azaleas from winter dehydration with extra watering before the first hard frost, then add a thicker layer of mulch to prevent evaporation. Evergreen azaleas continue to lose water through their leaves in winter, but their dormant roots can't take up any new water. Build a temporary screen around them using wooden stakes and burlap to protect them from desiccating winds.

Azalea Varieties

There are over 10,000 azalea cultivars, as they have been cultivated by American gardeners since the 1830s. Some are better suited for southern climates and don't do well in the north—and vice versa. If you are planting more than one, choose different complementary colors to highlight their differences. The American Rhododendron Society regularly registers new hybrids, descendants of both tropical and temperate varieties. North American natives are better at attracting pollinators, and the early blossoms are especially welcome for hungry bees just emerging from hibernation.

Easy-to-Grow Native Azaleas
Variety	Blooms	Colors	Height (feet)
Coast (R. atlanticum)	mid-May	White	3-5
Mountain (R. canescens)	April	Pink	6-8
Flame (R. calendulaceum)	May	Orange	8-10
Sweet (R. arborescens)	June-early July	White	6-8
Rose-shell (R. prinophyllum)	May	Pink	4-8
Pinkshell (R. vaseyi)	late April-May	Pink, White	5-6
Swamp (R. viscosum)	mid-June-July	White	5
Oconee (R. flammeum)	April-May	Yellow-orange, Red	6-8