Extending Azalea Blooming Season

Extending Azalea Blooming Season

When I first moved to Tyler, I soon fell in love with azaleas. The Tyler Azalea Trail, held annually at the end of March through early April, captivated me with miles of trails lined with homes displaying masses of brilliantly colored azaleas. Being the county Extension horticulturist, I made it my mission to learn as much as I could about azaleas. So, I endeavored to know the names of all popular azaleas that bloomed at that time. Foolish man! There are literally thousands of azalea varieties, although there are limited numbers of varieties commonly seen, grown and available to purchase. The second edition (1988) of the classic book Azaleas by Fred C. Galle, former curator of Callaway Gardens, lists all the azalea species (about 60) and 7,000 different azalea varieties, from dozens of hybrid groups. Even though only a limited number of these are commonly grown in a typical landscape, it shows how difficult it can be to identify an azalea just by looking at a blooming shrub.

The Tyler Azalea Trail is located in the older part of Tyler along many miles of red brick-paved streets, making the displays even more special. Azaleas were first brought to Tyler in large numbers during the late 1920s by Maurice Shamburger, an early Tyler nurseryman. He had experimented with some azaleas in his home landscape, and being impressed with their growth, and then encouraged by some local business leaders, he brought in hundreds to his nursery by boxcar from Georgia, where spring-blooming azaleas were common landscape plants and readily available in large numbers from wholesale nurseries. Eventually so many homeowners landscaped their homes with these early-blooming azaleas that the Tyler Azalea Trails began in 1960.

Many of these azalea varieties were derived mostly from two hybrid groups that generally bloom in Tyler in March through early April. The concentrated timeframe of blooming season results in riots of color with blooms so dense on the shrubs that you can barely see any foliage. Most of the azaleas on the trail are early-blooming. One of these groups is the Southern Indica hybrids. These large shrubs typically grow to six-to-eight feet tall and wide, with large leaves and equally large blooms.

The other group of early bloomers are the Kurume azaleas. Kurume azaleas are generally smaller, more compact shrubs with smaller leaves and blooms. Many of the landscapes in the Tyler Azalea District use the smaller Kurume varieties, like ‘Hinode Giri’, ‘Coral Bells’ (a very early bloomer) and ‘Snow’ in front of their larger Southern Indicas, such as ‘Mrs. G. G. Gerbing’, ‘Pride of Mobile’, ‘George Lindsey Taber’, ‘Formosa’, and ‘Judge Solomon’.

Several deciduous, native azaleas also bloom in very early spring, usually showing off their beautiful and fragrant flowers before they flush out a new set of leaves. Rhododendron canescens (Piedmont or honeysuckle azalea) and R. austrinum (Florida or flame azalea) and their hybrids fall into this category. Not only do they start the azalea-blooming season, but their upright growth habit makes them stand out like shining stars in the landscape. Other deciduous azaleas will bloom a bit later in spring, reaching peak bloom later in April. (For more information on this outstanding group of plants, see my article in the March/April 2022 issue of Texas Gardener.)

While learning about azaleas, I discovered that there are many types that bloom a little later than varieties commonly grown along the Trail. These are considered mid-season bloomers. One of the groups that has a large number of mid-season bloomers is the Robin Hill hybrids. Some popular representative varieties include ‘Robin Hill’, ‘Cory’, ‘Conversation Piece’, ‘Watchet’ and ‘Nancy of Robin Hill’.

Another mid-to-late season blooming hybrid azalea group is the Carla hybrids, originally bred at North Carolina State University. The breeder later transferred to Louisiana State University and evaluations of the breeding work continued there. Their breeding goal was to produce cold-hardy, root-rot resistant and drought-resistant azaleas. One of the more popular azaleas that is often available in the South is ‘Sunglow’. I have a few of these, and the cultivar name aptly describes the brilliant show they put on in mid-to-late April in my Tyler garden.

Many other cultivars bloom in what might be considered mid-season. A few examples include ‘Ben Morrison’ (a Glenn Dale hybrid); ‘Red Slippers’ (a Back Acres hybrid), ‘Carror’, (a Carla hybrid) and ‘Elsie Lee’ (a Shammarello hybrid).

A hybrid group that blooms even later is the North Tisbury hybrids, which exhibit the ground-hugging characteristics of one of its parents — R. nakaharai. They tend to bloom very late in the spring and can be used as a groundcover shrub. However, these tend to be somewhat hard to locate in commerce.

Another, even later-blooming hybrid group is known as Satsuki azaleas. As you might guess, Satsuki is a Japanese word, and it means “fifth month” because in Japan and in the South they bloom in May. Once I realized that these azaleas were designed to bloom later in the season, it dawned on me that they made it possible to have a continuous azalea-blooming display from early March to early June if you carefully chose your varieties. There are hundreds of Satsuki varieties in Japan, and several are popular landscape plants in the southern United States. Many Satsuki varieties are compact, medium-sized shrubs, with very large blooms. As a group, they tend to be rather slow-growing.

‘Gumpo White’ and ‘Gumpo Pink’ are two Satsuki azaleas commonly available in nurseries in the South. These are very compact evergreen shrubs with very large pure-white or bright-pink flowers. These particular varieties are not heavy bloomers, but they make up for that limitation with the size of their flowers. The rest of the year, their tight, low, evergreen growth habits make them great candidates for the front of a lightly-shaded flowerbed.

The Satsuki azalea ‘Wakaebisu’ is one of my favorite azaleas that I grow. It is compact, slow-growing and has no problems in my landscape. It puts on a heavy display of hose-in-hose pink flowers after most of my other azaleas have finished blooming. Some other popular Satsuki varieties include ‘Amagasa’, ‘Gyokurin’, ‘Gyokushin’, ‘Flame Creeper’, ‘Higasa’, and ‘Waka Matsu’.

One of the latest of the spring-blooming azaleas in my Tyler garden is the native Texas azalea (R. oblongifolium). This deciduous azalea blooms in mid-May, usually at the same time my oakleaf hydrangeas (Hydrangea quercifolia) are blooming. My 25-year-old specimen is a cutting from a plant growing wild along a small creek bank in the yard of one of my Master Gardeners, when I was a Texas A&M AgriLife County Extension horticulture agent. While it is not a showstopper, it carries a lot of meaning for me.

I would be remiss if I did not mention the reblooming azalea varieties which have become very popular in recent years. I wrote about these in a recent Texas Gardener article (November/December 2021). These varieties not only bloom heavily in the spring, early-to mid-season depending on variety, but they will reliably repeat-bloom later in the fall and early winter. Here in mid-December as I write this article, I currently have the following Encore series in bloom: Autumn Sunset, Autumn Royalty, Autumn Twist and Autumn Sunburst. I have a friend who was unfamiliar with these types of azaleas and who commented on my social media about a photo of a Bloom-A-Thon variety blooming in November. Not realizing it was purposely bred for that trait, she thought it seemed way too early for azaleas to be blooming in November. There are several branded and trademarked reblooming types now on the market, including Encore, Bloom-A-Thon, Deja Bloom and others.

In addition to these newer trademarked azaleas, there are several other reblooming, non-trademarked azaleas that provide beautiful color in both spring and again in the fall. Some of these include ‘Watchet’, one of my favorites that I grow; ‘Chinzan’, a Satsuki; ‘Fashion’ and ‘Conversation Piece’, blooming now in my garden in mid-December; ‘Red Slippers’, a Back Acres hybrid; ‘Janet Rhea’; a Linwood Hardy hybrid; and ‘Hardy Gardenia’, a Satsuki. ‘Koromo Shikibu’, a light-purple spider azalea, is another repeat fall-bloomer and is the signature plant for the Gayla Mize and Ruby Mize Gardens in the SFA Gardens in Nacogdoches. The SFA Gardens are a great place to see an amazing number of different azalea varieties, and you cannot miss the 800-foot plantings of ‘Koromo Shikibu’ lining both sides of University Blvd.

I learned a design trick from Steve Brainard, past president of the Azalea Society of America and designer of the initial planting of the Ina Brundrett Azalea Garden located on the campus of Tyler Junior College. He said if early and mid-season varieties were planted right next to each other, the fading blooms of the early-blooming azaleas would distract from the newly opened blooms of the mid-season bloomers. So, for a cleaner look, plant each in blocks with some separation.

I have seen landscapes where many different azalea varieties are all mixed together without regard to bloom color and mature height. The result can be a rather garish, busy display and not easy on the eye. A more pleasing use of azaleas is to mass several plants of the same variety together to create a colorful impact. Take care if you use more than one variety to ensure the colors complement one another rather than clash. A taller, upright growing deciduous azalea variety can add a dramatic touch to any landscape. I am not an artist nor a landscape designer, and beauty is in the eye of the beholder, but hopefully these suggestions will help you create an attractive and eye-catching display of these beautiful plants.

I have repeatedly referred to several different hybrid groups of azaleas. Each hybrid group is not a homogenous collection of plants with identical characteristics. Actually, they can have several different parentages with varying genetics. So, not all azaleas within a certain hybrid group will always have similar bloom times or mature sizes. When making decisions on purchasing any particular plant for your landscape, always research about all its characteristics to make sure it fits in with your overall design goals.

Keep in mind that the designations of early-, mid- and late-season blooming times are relative to the different varieties of azaleas. Timing of bloom of any azalea variety can vary from year to year, depending on the weather. There have been years when the Tyler Azalea Trail, which is annually scheduled for peak azalea bloom during the last week of March through the first week in April, when the azaleas on the trail were not at their peak. One year, blooming had already started peaking at the beginning of the official trail date due to a very mild period in February and March. Another year at the grand opening, there were hardly any blooms open yet due to an abnormally cold February and March.

With a little bit of planning, you can use azaleas to create islands of color starting in early March and continuing through late spring. Add a cluster of fall-blooming azaleas to extend the enjoyment of these beautiful plants through much of the year. If you have a partly shady yard with well-drained, acidic soil, a few strategically placed beds of azaleas blooming at different times of the year will add interest and pleasure to your garden for years to come.

By Keith Hansen
Smith County Horticulturist, Emeritus
Texas A&M AgriLife Extension Service
Owner, East Texas Gardening