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US National Arboretum


Azalea Blossom Watch 2014
Current Conditions

April 11 | April 23 | May 2 | May 22

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 11

Spring has finally sprung.  The cherries and daffodils are currently in full bloom, roughly 10 days behind usual.  The cold temperatures experienced in the mid-Atlantic region this winter put us back into a solid zone 7 [average night time low of 0-10 degrees F].  This year, marginally-hardy plants that might have wintered fine for the past 5 years, may have suffered winter burn, bud blast, bark splitting or they might have perished altogether.  We lost a hardy gardenia.

The Azalea Collection has had few casualties –the damage most seen is leaf scorch from winter cold and wind.  Cultivars with Rhododendron indicum,  [a zone 8 species used in breeding for evergreen foliage, large flowers and late blooming properties] as a parent are showing some damage to the foliage.  Most of them survived and will grow out it.  Cultivars using R. kaempferi [a zone 5 species used to instill hardiness, early blooms, color ranges and height] as a parent are almost deciduous this year but their flower buds are intact and ready to bloom in just a few weeks.   This includes many of our Glenn Dale azaleas.  Species using R. poukhanense [a zone 6-7 species used for larger flowers, the lavender colors, foliage and lower growth habit] also appear to be deciduous this year.  Rhododendrons with larger evergreen leaves may have winter burn in the form of leaf scorch.  The damaged leaves will drop off in June as the new foliage emerges. 

Yesterday while working on the southern side of the Glenn Dale Azalea Hillside, I detected the first signs of bud color.  We are about 10 days behind our normal average for bloom.  I expect our peak bloom weekend to be at the end of April to early May.  Happy Spring, everybody!  See you in the garden!  

 April 23

Spring is slowly unfolding at the National Arboretum.  We are still about two weeks behind our usual sequence.  There are several azaleas in bloom that always bloom early along with the daffodils and dogwoods.  Rhododendron kaempferi (the Torch Azalea) and R. poukhanense (the Yodogawa Azalea) are two azalea species used in breeding to create early bloomers.  Examples currently in bloom are ‘Corsage’, ‘Lilacina’, ‘Vicki’ and ‘Kinshibe’.

The Weston hybrids have started to bloom this week.  Weston's 'Landmark' is one to see with its striking deep magenta flowers and dark burgundy evergreen foliage.  The Nearing hybrid, 'Montchanin' is lovely with clusters of tiny pale pink flowers and dark evergreen leaves.  Both plants are located along the trail entering the Azalea Collections from the end of the Flowering Tree Walk near the Capitol Columns Overlook.  

The Kurume hybrids are about to open any day, as are the Glenn Dale hybrids located on the south side of Mt. Hamilton.  One only need look closely to see colorful buds and a few opened flowers.  Several warm, sunny days will encourage more and more flowering.  We hope to see you in the garden.

 May 2

Glenn Dale HillsideThe Azalea Collection will be at peak bloom the weekend of  May 3rd -4th.   Peak bloom is when about 50% of the azaleas are either in  bloom, beginning to bloom  or almost finished blooming. Each azalea shrub blooms for approximately two  weeks.  Based on the location of the azaleas, the plants on the south slope will be in bloom one week ahead of those on the east slope.   The cultivar collections of the Morrison Garden (Glenn Dales), Lee Garden (Satsuki’s), and Loop Area (Kurume’s, North Tisbury’s, Robin Hills, and color groupings) will be coming into their peak season during the week of Mother’s Day, May 11th . 

Planted on the east side of the collection are cultivars of evergreen and deciduous azaleas as well as some larger leafed  rhododendrons.  The Kurume hybrids are the first of the evergreen azaleas to bloom and they are located across from the Capitol Column overlook. They are in peak bloom this week.  Due to this year’s cold winter,  our evergreen azaleas lost many of their leaves.  This occurs every year, but it is more noticeable this year.   By early May, the new growth will flush out.

The azalea native to our own Washington D. C. forests is in bloom this week as well. Known as the “Pinxter Azalea”, Rhododendron periclymenoides is a light pink flowered deciduous azalea. It can be found throughout the woodlands on the western slope of Mt. Hamilton and in the Fern Valley Native Plant Collection.

May 22

R. austrinum in with purpleWhile the peak show of azalea blooms has passed, there are many azaleas still in bloom today and many more going to bloom.  One of the primary objectives of first USNA Director, B. Y. Morrison’s azalea breeding program was to extend the season of bloom for azaleas.  Known collectively as the Glenn Dale azaleas, these can be seen growing in and around the Morrison Garden and are planted throughout the Azalea Loop within their color groups. 

Other azaleas in bloom are the Robin Hill, North Tisbury and Satsuki hybrid groups.  Each group is planted together in collections along the Henry Mitchell Cultivar Walk.  The Robin Hill azaleas have larger flowers and are generally less than five feet tall.  The North Tisbury’s have lustrous dark foliage with brilliant pink, red, or orange flowers.  All of the North Tisbury’s are fairly low growing and spreading.  They are selections of the Japanese species Rhododendron nakaharai.  One of the selections ‘Nakami’ grows only one inch tall.

The larger leaf Rhododendrons are also coming into bloom.  Requiring ideal drainage and a lot of space, they are creating a spectacular show this week throughout the azalea collection as well as in Fern Valley, the Dogwood Collection and the Asian Collection.  See you in the garden!


Click here for other images of the collection.

You can also read the Azalea Blossom Watch from
2013, 2012, 2011, 2010, 2009, 2008, 2007, 2006, 2005, and 2004.

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Last Updated   May 23, 2014 11:58 AM

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