THIS TIME OF YEAR, you can step outside just about anywhere and be dazzled by the abundance of blossoms and emerging leaves. However, if you want to feel completely overstimulated, take a few shots of espresso and head to the Washington Park Arboretum in the next couple of weeks. Azalea Way, the Arboretum’s central feature, and perhaps the most celebrated plant collection in the city, is a classic spring destination for a reason.
Azalea Way was once a logging road, then a horse-racing track and now a picturesque botanical garden. This wide, flat tract was designed and planted early in the Arboretum’s history, intended as a springtime showcase. Just think: Decades of work have been invested just so you can meander down a path on a beautiful sunny day surrounded by flowers.
But before you race off for the Arboretum, how about some background on these eye-catching and amazing plants? It would be almost irresponsible to frolic through those verdant fields without a bit of botanical and geological history, especially with all that coffee in your system.
First things first: Azaleas are types of rhododendrons. Rhododendron is a genus in the Ericaceae family, a huge clan that includes other highly lauded plants such as the blueberry, cranberry and huckleberry. The rhododendron genus itself is amazingly diverse, with more than 1,000 separate species and countless cultivated varieties. Their ranks include species ranging in size from 4 inches to 100 feet, and their inclination for hybridization leads to an inconceivable array of flower shapes and colors. In fact, their divergent morphology led to centuries of hand-wringing, as botanists attempted to devise a classification structure that could properly contain them.
Rhododendrons are also notable in the breadth of their natural distribution. They’re widely distributed across Europe, Asia and the archipelagoes spreading southeast from Asia all the way to Australia. While some species prefer low-lying regions, rhododendrons are generally keen on elevation, and typically are found in the mountainous regions of their native territories.
The majority of rhododendron species is found in the southern Himalayan mountains and southwest China. This area, with vast expanses of mountainous terrain, provides perfect rhody habitat. Given this cluster of diversity, it is logical to assume the plants first evolved in this region. However, a fossilized rhody leaf imprint found in Alaska, dating back 50 million years, tells a more complex story. The implication of this find is that rhodies could not have evolved in the Himalayas, because the Himalayas didn’t exist 50 million years ago — remember? Surprisingly, the distribution of rhododendron species over geological time is a woefully underfunded area of research. Thus, we might never know the true location of their origin.
While rhodies are native to most of the temperate regions of the Northern Hemisphere, they are oddly lacking throughout much of North America. There is a handful of species endemic to the southern Appalachian Mountains and a single species (Rhododendron occidentale) native to the West Coast. One leading theory is that these plants were once abundant across much of our continent until wiped out by glacial encroachment, possibly as recently as the Last Glacial Maximum.
While we might not have the opportunity to explore many rhododendrons in the wilds of Washington, we have more than our fair share at local parks, botanical gardens and neighborhoods. Azaleas and other rhododendrons are usually in bloom from mid-April through the end of May in our part of the world. So take the opportunity to get outside and thank these visitors from far-flung locales for making our springtime so bright and cheery!