American Evergreen: Rhododendron Refuge

The evergreen Rhododendron is an iconic shrub in the Eastern US. Indeed, it is hard to imagine our landscapes without it. Its big shiny leaves and glorious spring flowers make it a year-round favorite.

The two best-known native evergreen “rhodies” in the Eastern US are Catawba (Rhododendron catawbiense) and Rosebay or Great Laurel (Rhododendron maximum). Catawba is the rhodie we see most often in suburban landscapes, either the native species with pinkish-purple flowers, or one of the many hybrids with non-native species, such as ‘Roseum Elegans’ and ‘English Roseum.’ The shrubs you see blooming in mid-spring with big showy flowers ranging in colors from pale pink to hot fuchsia usually are Catawba hybrids.

Rhododendron catawbiense in bloom

Rhododendron maximum is larger, with big, slightly floppy leaves and pinkish-to-white flowers that bloom a few weeks later than the Catawbas. While Catawba shrubs typically reach 8 to 10 feet tall and wide, Rosebay can top out at 15 to 25 feet with an equally wide spread.

Rhododendron maximum

Though Catawba’s original range was in the Southeast, from Virginia to Georgia, it performs very well in Zones 5 to 8, so it is a good choice for gardens in New York and the mid-Atlantic region. Rosebay Rhododendron is native from Maine all the way to the mountains of Tennessee, and hardy in Northeastern winters through Zone 4. Both shrubs prefer rich acidic soil and moist-to-dry conditions in sun to part shade. Protection from very hot afternoon sun and supplemental water during prolonged drought is recommended.

Evergreen Rhododendrons in the wild can form massive, impenetrable thickets that shade out competing plants, including trees. In the Appalachians, Rhododendron thickets viewed from a distance are so dense and treeless that they make the hillsides appear smooth. Locals call them Rhododendron “slicks” or “balds” because they look almost like lawns on distant hills. Up close, however, the reality has earned them the name rhododendron or laurel “hells.” Hikers, hunters, and their dogs, have been lost for days, unable to find their way out of the tangle of branches — too tall to see over, and too dense to see through. But Rhododendron thickets have also served as a refuge for both humans and animals.

The Nature Center’s Native American long-house is partially hidden by
a Rhododendron thicket

In 1838, under authority of the Indian Removal Act, the United States government forced more than 16,000 Cherokee people to leave their homelands in Tennessee, Alabama, North Carolina, and Georgia, marching them to Oklahoma along the tragic “Trail of Tears.” The Cherokee people of Nantahala in North Carolina, however, resisted the round-up by government troops and fled to “laurel hells” in the Nantahala River Gorge. Led by Oochella, “a man who made himself somewhat notorious by threats of resistance,” the Nantahala fugitives evaded the military by hiding in what one contemporary journalist described as “the most gloomy thicket imaginable… Even at noonday, it is impossible to look into it more than a half dozen yards, and…no white man is yet known to have mustered enough courage to explore the jungle.” Eventually, after a number of lethal skirmishes, government troops granted amnesty to the remaining fugitives and withdrew. Oochella and his followers joined the Qualla Cherokees and formed a community that survived as the Eastern Band of Cherokee Indians.

In modern landscapes, the dense evergreen cover of Rhododendrons makes these shrubs ideal as privacy screens. Instead of a tight row of clipped Arborvitae or a taxus hedge, a screen of Rhododendron provides much greater visual interest, as well as critical habitat for pollinators and birds. In spring, the enormous flower clusters provide nectar and pollen for bees and butterflies, and throughout the year, evergreen Rhododendrons are safe hiding places for birds.

A red-bellied woodpecker hunts in the Rhododendron
A hairy woodpecker rests under cover

It is no exaggeration to say that evergreen Rhododendrons planted next to your house will give you bird-watching opportunities in every season. Even on the coldest days of winter, when freezing temps cause Rhododendron leaves to curl tight to avoid damage, winter birds will seek refuge in the Rhododendron.

Each of these photos was taken from a window looking into a Rhododendron:

Rhodies grow fairly fast, are easy to care for, and provide critical habitat. Deer will eat Rhododendron leaves if they can reach them, but only if there is nothing else available. The leaves are actually toxic to most mammals, including horses, sheep, and cattle, so it is a last choice for deer, too. Fencing at the base of the shrub, especially when it is young, helps protect it until it grows out of reach.

Rhododendron catawbiense is an effective, and attractive, privacy screen

For more information about evergreen Rhododendrons, including their strange
ability to tell you the outdoor temperature, click here.

THIS BLOG IS WRITTEN BY CATHY LUDDEN, CONSERVATIONIST AND NATIVE PLANT EDUCATOR; AND BOARD MEMBER, NATURE CENTER at greenburgh. FOLLOW CATHY ON INSTAGRAM FOR MORE PHOTOS AND GARDENING TIPS @CATHYLUDDEN.

How Cold Is It Outside?

How cold is it outside? Let’s check the Rhododendron to find out….

Not too bad — definitely above freezing:

Leaves are flat and parallel to the ground.

Now it’s around freezing:

Leaves are still open, but drooping.

Oh, it’s colder now, around 25 degrees:

Leaves begin curling.

Yikes! It’s really cold now, 20 degrees or colder:

Leaves are curled up as tight as cinnamon sticks!

The Rhododendron is surprisingly accurate as a cold weather thermometer. Its leaf-rolling trick protects the leaves from damage due to rapid freeze and thaw cycles by reducing surface area. This defense helps it thrive as an evergreen.

The genus Rhododendron is ancient. Fossils of Rhododendrons over 50 million years old have been found in Alaska. The name is Greek from rhodos meaning rose and dendron meaning tree. There are over 1,000 species of the “rose tree” on Earth, ninety percent of them found in Eurasia. There are tens of thousands of hybrids and cultivars. 

In the US, there are only 27 native species of Rhododendron, and most of them we know as azaleas. Azaleas are part of the same genus, but their flowers have 5 stamens rather than 10, and virtually all of our native azaleas are deciduous, dropping their leaves in the fall.

The evergreen Rhododendron is an iconic shrub in the Eastern US. It is hard to imagine our landscape without it. Its big shiny leaves and glorious flower clusters in late spring make it a year-round favorite. The two native evergreen “rhodies” in our region are Catawba (Rhododendron catawbiense) and Rosebay or Great Laurel (Rhododendron maximum). While Catawba’s native range is further south, in southern Appalachia and the Piedmont, Rosebay dominates the northern territory from eastern Maine all the way to Georgia. Both do well in rich acidic soil and moist woodlands. Catawba is the one we see most often in our suburban landscapes, either in its native form with pinkish-purple flowers, or hybrids like ‘Roseum Elegans’ and ‘English Roseum.’ The big showy flowers we see in mid-spring in a range of colors from pale pink to hot fuchsia usually are Catawba hybrids. Rosebay Rhododendron, with larger, slightly floppy leaves, and pinkish-white flowers, grows taller and blooms a few weeks later.

Both shrubs make great privacy screens. Left to their own devices in the wild, both Catawba and Rosebay can form massive, impenetrable thickets that shade out competing plants, including trees. In the Appalachians, Rhododendron thickets viewed from a distance are so dense and treeless that they appear smooth. Locals call them Rhododendron “slicks” or “balds” because they look almost like lawns on distant hills. Up close, the reality has earned them the name “rhododendron hells.” 

The Nature Center’s Native American long-house is partially hidden by a Rhododendron thicket

On the other hand, birds do love a thicket! A big Rhododendron close to the house will give you a bird-watching site all year around.

A red-bellied woodpecker pokes around in the Rhododendron

Rhododendron is known to be toxic to horses, sheep, and other grazing animals. So, it is a mystery how deer manage to strip leaves within their reach. No doubt they prefer other food, but they seem to know just how much Rhododendron they can eat without ill effects; and they may do that.

But on those bitter cold days when the rhodie leaves curl up just as tight as they can, it helps to have a warm drink, and think about what that shrub is planning for you for spring.

Catawba rhododendron in late May. Sigh.

This blog is written by Cathy Ludden, conservationist and native plant educator; and Board Member, Greenburgh Nature Center. Follow Cathy on Instagram for more photos and gardening tips @cathyludden.