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US National Arboretum


Azalea Blossom Watch 2013
Current Conditions

April 5 | April 17 | May 6

Experience the National Arboretum's treasured Azalea Collections

Spring is upon us once again, and the National Arboretum is rich with bloom from the spring ephemerals to the daffodils, magnolias and cherries planted throughout the grounds. This column which begins today and will change each week for the next eight weeks will focus specifically on our Azalea Collections and the status of bloom.

Experience the explosion of color when thousands of azaleas at the National Arboretum light up the forest with their subtle shades and colors.However, the first azaleas begin to bloom in early April with the daffodils and the forsythia, and still others are blooming as late as July with the daylilies. We hope that this Azalea Blossom Watch will give you insight into the range and diversity of the Rhododendron species and cultivars growing at the National Arboretum, as well as help you with planning your visit.

Images of azalea blossoms

The best time to schedule your visit is on a weekday, but if weekends are your only option, a stroll through the garden before noon or during a light rain offers an enviable second choice. A drive around Azalea Road can be exhilarating because of the views of the collection, but if you can afford the time to take a walk, it is worthwhile. Pick up a brochure at one of the three major entrances to the collections or at the Visitor Information center and begin your journey into the world of azaleas.

Learn more about the Azalea Collection here. For more in-depth information on growing and caring for rhododendrons or azaleas, check out the FAQ pages here. Visit our Azalea Photo Gallery where you will find over 200 images of the flowers of more than 100 of the Glenn Dale azalea varieties.

In the meantime, check back here each week as we update you on the current conditions in this year's Azalea Blossom Watch.

April 5

R. reticulatumGreetings to our friends and guests!
Today we begin our weekly azalea blossom watch updates. For the next eight weeks, Azalea Collections Curator Barbara Bullock will describe the azaleas as the season unfolds.

Peak Bloom Prediction
Spring is taking the slow approach this year. With temperatures hovering on the cool side (daytime averages in the mid-fifties throughout the month of March), the azaleas are not quite ready to show their colors. As long as temperatures remain cool, we predict peak bloom to be around the end of April or early May. 

Current Conditions
Some early Rhododendron species are in full bloom in the Azalea Collections: R. mucronulatum (lavender), R. keiskei  (pale yellow) and R. reticulatum (pinkish-lavender). All over the National Arboretum, cherries, magnolias, and daffodils are loving the cool, bloom-sustaining temperatures. 

R. keiskeiGlenn Dale Hillside Rejuvenation Project
Something new happened in the Azalea Collections this year. The popular Glenn Dale Hillside underwent one of the most significant renovations in its sixty-six year history. During the past month, about 75% of the 4,000 azaleas received a treatment known as rejuvenative pruning. We cut the older, rangy branch growth at ground level, leaving the shorter, newer growth intact. While the bloom display will be less this year, in only a few years the azaleas will rebound better than before, amazing thousands of visitors as they always have. 

Sapling and Invasive Removal
In addition to the rejuvenative pruning, we have implemented tree sapling and invasive plants removal. Our goal is to leave fewer saplings to reforest the hillside, so that optimum light conditions exist for the azaleas—a mix of sun and shade. Perhaps the most important part of this initiative is invasives removal. You will see a lot less English ivy when you visit the hillside this spring. 

We’ll see you in the garden!

April 17

Rhododendron-keiskeiPeak Bloom Prediction
We are still expecting the azaleas to peak around the end of April or early May. The Glenn Dale azalea hillside is at 10% bloom this week, but with buds showing color all over, we think this weekend will be about 25% open. With the March thinning of the older Glenn Dale azaleas, visiting the hillside this spring feels a lot like it must have when the Arboretum first opened its gates in 1958 for visitors to see the colorful display. 
Rhododendron-Weston-hybrid-'Olga-Mezitt'-Current Conditions
Some early Rhododendron species blooming this week in the Azalea Collections: R. mucronulatum (lavender), R. keiskei  (pale yellow) and R. reticulatum (pinkish-lavender).  Always the first of the evergreen azaleas to bloom, the Kurume azaleas are blooming at about 75%. The Weston lepidote rhododendron hybrids are also in bloom. The unveiling of spring has also yielded tulips, later daffodils, later cherries, redbuds, dogwoods, and forsythia this week.

We’ll see you in the garden!  

May 6

View of north side of Azalea CollectionsCurrent Conditions
The azaleas are in full bloom. This spring's sustained cool temperatures have helped prolong the bloom period, resulting in a remarkable display: We are still enjoying the flowers of our earliest group of evergreens to bloom, the Kurume azaleas, while the mid-season shrubs begin their show.

Kurume Azaleas
The Arboretum’s first director, Benjamin Y. Morrison, used Kurume azaleas in his Glenn Dale azalea breeding project to impart hardiness, foliage, and form. All of the Kurume azaleas are wonderfully picturesque even when not in bloom.  

Deciduous Azaleas
Joining the mid-season symphony of color are the many deciduous azaleas with colors that contrast nicely with the evergreens. Deciduous azaleas can be found in many areas of the world. There are 14 species of native deciduous azaleas in North America. Several of these are in bloom today. Rhododendron atlanticum (the coast azalea), known for its heavenly fragrance, can be found in several places in the Azalea Collections—most notably at the entrance to the Frederic P. Lee Azalea Garden.

Glenn Dale Azaleas
This is the main time to view the Glenn Dale azaleas, 454 of which were introduced by Benjamin Y. Morrison by 1953. Morrison crossed the early Kurume azaleas recently imported from Japan with the later, larger blooming species and hybrids also from Japan to create this spectacular hybrid group. 

This is the perfect time for you to plan your visit.  See you in the garden!

Click here for other images of the collection.

You can also read the Azalea Blossom Watch from
2012, 2011, 2010, 2009, 2008, 2007, 2006, 2005, and 2004.

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Last Updated   May 8, 2013 7:15 AM

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