Azalea Plant Profile

pink azaleas

The Spruce / Adrienne Legault

Is there a more welcome sight in spring than an azalea shrub in full bloom? These shade-loving plants can bring delightful color to all corners of the spring garden. Heirloom varieties can grow as high as twelve feet tall, with spectacular displays in spring. The range of colors is spectacular, from white to pale pink to a range of reds and purples. Most azaleas bloom in mid-spring (mid to late April), but some bloom earlier or later than others, and it's easy to choose a variety for your design needs. Like their larger cousins, the Rhododendron ferrugineum, the azalea's thick leaves can remain evergreen, though most varieties grown in the United States are deciduous.

In the garden industry, the names "azalea" and "rhododendron" are often used interchangeably, which can become confusing. One way to tell them apart at first glance is the size and shape of the blooms: traditional rhododendrons have large round clusters of flowers, whereas azalea blooms are more evenly distributed on the entire shrub. Rhododendron leaves are also larger, fleshier and darker green than azalea leaves. There are numerous cultivars, so do a bit of research before you buy to make sure you get the plant best suited for your needs. For example, some varieties are more cold hardy than others. There are also now many azalea-rhododendron hybrids, which makes for very hardy plants that are a more manageable size and that have a wide range of flower colors.

Botanical Name Rhododendron
Common Name Azalea
Plant Type Deciduous or evergreen shrub
Mature Size 3' to 12'
Soil Type Acidic
Soil pH 5.5 to 6.0
Bloom Time Early to late spring
Flower Color White, pink, red, orange
Hardiness Zones 3 to 9 (3 to 7, 5 to 9)
Native Areas Asia, Europe, North America
   
azalea shrub

The Spruce / Adrienne Legault

closeup of pink azaleas

The Spruce / Adrienne Legault

red azaleas

The Spruce / Adrienne Legault

Row of bright pink azaleas by a lake and rock wall reflecting in the water
These hot pink azaleas in a botanic garden in Seattle show how dramatic these spring favorites can be in the garden.  Aurora Santiago / Flickr / CC BY 2.0

How to Grow Azaleas

Proper planting is key to success with these long-lived shrubs. Amending the soil will probably be necessary to ensure it gets a good start: have some peat moss and compost on hand to mix in with some good soil. Water in when planting and water daily for the first week until established.

Light

Azaleas flourish in shady spots, though they like a bit of sun: a few hours of morning sun is best, so the flowers don't wilt if a spring day becomes too hot. Most azaleas stay in bloom for about two weeks, barring rain or wind damage from a storm.

Soil

Azaleas love acidic soil; this explains why potted nursery plants usually have mostly peat moss for the planting medium. Soil should also have good drainage and good fertility with plenty of organic matter (compost, chopped leaves, etc.) and azaleas do best with a natural mulch such as pine bark mulch.

Water

Azaleas need water to bloom, and spring rain showers usually do the job. However, if the spring is dry, extra watering can be beneficial.

Temperature and Humidity

Azalea hardiness ranges between 3 and 9, with most of them having a narrower range at one end or the other (3 to 7 or 5 to 9). With ranges this narrow it's important the choose your plant and your planting site carefully. Too cold, and buds may not form; too hot, and flowers may burn from over exposure. Mildew can be a problem with azaleas; make sure they have plenty of air circulation and don't plant them too close to other large shrubs.

Garden Design Suggestions

Azaleas look great planted beneath trees or at the back of a border. They can make a great specimen planting in a prominent place by an entrance or patio also. Since the flowers are so showy, ideally you want your azaleas to bloom when your garden needs a boost of spring color. Maybe after your early blooming daffodils are fading, and before the peonies light up? You could also coordinate tulip plantings for striking color combinations. Consider orange tulips (like April-blooming "Orange Emperor" tulips) with pink azaleas, or purple tulips (like "Passionale" or "Negrita") with white or red azaleas. Having more than one variety of azalea with overlapping spring bloom times is an ideal scenario. There are some reblooming cultivars (the "Encore" series) that will give you blooms from spring through late summer.

Varieties to Choose

One can't flip through a garden catalog without seeing a new variety of azalea.Here are some tried and true ones, including newer hybrids.

"Rosy Lights" : This compact (4' to 6') deciduous cold hardy (USDA 3 to 7) shrub blooms in late spring and features a sprightly flower in a rosy red color with hues of coral and blush. This is one of the "Northern Lights" azalea-rhododendron hybrids. The flowers are borne in "trusses" - not as round as traditional rhododendrons but not as diffused as traditional azaleas.

"Windbeam" : With smaller leaves and a tidy habit (3' to 4'), this popular cultivar features luminous pale pink flowers and olive green leaves that turn bronze in autumn. Hardy in Zones 4 to 8, it may need shelter from harsh winter winds, but it is more sun and heat tolerant than other azaleas. The spring display is stunning, beginning white and evolving to pink with tiny red freckles on the dorsal lobes.

"Golden Lights" : The bright golden-orange blooms on this "Northern Lights" cultivar offer a dramatic color for the spring landscape. Cold hardy (USDA 3 to 7) and compact (3' to 6'), the flower trusses are flat and contain ten flowers each, in shades ranging from butter yellow to orange with salmon pink highlights.

"Fragrant Star" : The pure white flowers on this small (3' to 4') mid-spring bloomer have a heady, spicy fragrance. The leaves are a pleasing bluish green. It is quite heat tolerant but not as cold hardy as others (USDA 5 to 9), though can withstand cold temperatures as low as -20F, if sheltered from harsh winds.

"Gibraltar" : This popular azalea boasts frilly, faintly fragrant, bright orange flowers that emerge from crimson buds. It is medium height (4' to 5') and relatively cold hardy (USDA 5 to 8). This variety is also very mildew resistant.

Care and Maintenance

Azaleas benefit from mild pruning. They start forming buds in summer, so the best time to prune is right after the flowers drop off in late spring. Azaleas also do well if given some fertilizer. Without knowing the nutrients in your soil, a basic 15-15-15 fertilizer containing equal parts nitrogen, phosphorous and potassium is your best bet. But there are special products made just for azaleas: Espoma's "Azalea-Tone" is a good one. Fertilize in late winter or early spring, no later than the last week of March.