native shrubs Archives - Page 2 of 3 - Nature Center at Greenburgh

January 18, 2024February 6, 2025 Cathy Ludden Around the Grounds, Native Plants

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:

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

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.

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.

December 6, 2023February 12, 2025 Cathy Ludden Around the Grounds, Native Plants

Mighty Arborvitae

Arborvitae gets no respect.

Though Arborvitae (Thuja occidentalis) may be the most-planted tree in suburban America, it has been given a diminished role unworthy of this majestic native tree. Planted by the thousands along property lines by developers, builders, and landscapers, rows of crowded Arborvitae trees, standing shoulder to shoulder, have become the de-facto fences of suburbia.

A typical builder installation of Arborvitae

Without room to spread their branches or reach their natural height, Arborvitae is often topped and heavily pruned to form hedges. They handle this assignment very well, but Arborvitae can do so much more!

If you’ve only seen Arborvitae used as a hedge, it may surprise you to learn that in its natural habitat, it can grow 50 to 60 feet tall and live for hundreds of years! In fact, the largest known specimen is over 100 feet tall and more than 40 feet wide at the crown. The oldest living Arborvitae is thought to have germinated from seed in 952 A.D., and is now 1,071 years old! Based on ring counts on dead trees, there are verified specimens of Arborvitae that lived to be over 1,800 years old.

An ancient stand of Arborvitae on cliffs overlooking
Northern Lake Michigan
*Photo: C.J. Earle*

Arborvitae is one of the common names for Thuja occidentalis and means “tree of life” in Latin. It was named by the French sea captain, Jacques Cartier, when he was exploring Canada in 1536. After months at sea, Cartier’s crew, including two young members of the Huron native tribe who had been sailing with them, were all suffering from scurvy. On the way up the St. Lawrence River, Cartier dropped the two young men at their home village. When he later returned, he was astonished to find the two Hurons fully recovered from all symptoms of scurvy while his French sailors were still suffering. He asked the Huron elders to teach him the cure, and they showed him how to make a medicine, a tea rich in Vitamin C, from the foliage of Thuja occidentalis. Cartier brought the life-saving plant back to France, making it the first North American tree introduced to Europe.

The native habitat of Thuja occidentalis is swamps, low woods, and forest edges from northern Canada south to New York and Connecticut and west to Michigan and Northern Indiana. It is an evergreen conifer, extremely cold hardy, and adapted to poor rocky soils all the way to the edge of the Canadian tundra. Sometimes called Northern White Cedar, Eastern White Cedar, or Swamp Cedar, Arborvitae is not a true cedar in the Cedrus family, none of which are native to North America. But the fragrance of its foliage and bark, and the usefulness of its wood, are similar.

Arborvitae often grows in very thin, poor soil in northern
North America and is adapted to extreme cold. This forest of
Arborvitae is at the brink of the Niagara Escarpment in Northern Wisconsin.
*Photo: C.J. Earle*

The foliage of Arborvitae is flat and scale-like and has a spicy fragrance when crushed. Native peoples used it not only for medicine but also used the fragrant foliage as insect-repellant bedding. They stripped the tree’s shredding bark to make rope and twine, and they found many uses for the rot-resistant wood, including canoe frames and roofing shingles.

Thuja occidentalis has significant value to wildlife. It is a favorite food of white-tailed deer, as suburban homeowners often discover to their dismay. Twigs and foliage of Arborvitae constitute as much as 10 to 25% of the winter diet of deer, who will browse it as high as they can reach. In northern forests, the tree also provides highly nutritious food for snowshoe hares, porcupines, red squirrels, and beavers. Many native birds find nesting sites in Arborvitae and insects to feed their young. The seeds are the preferred source of food for Pine Siskins, birds indigenous to the Northeastern US.

It is sadly ironic that one of the most-planted trees in suburbia is disappearing in the wild. Thuja occidentalis is listed as Threatened in Connecticut, Illinois, Kentucky, and Maryland and Endangered in Indiana, Massachusetts, and New Jersey. Development is the primary culprit as forests are cleared to make way for more suburban homes.

It is equally sad that the rows and rows of Arborvitae planted on suburban property lines are not nearly as valuable to wildlife as they should be. The most popular varieties of Arborvitae are cultivars or hybrids that offer little value to wildlife – other than deer. A cultivar called ‘Emerald Green’ Arborvitae was developed in the 1950s in Denmark, just in time for the rapid expansion of the US suburbs after WWII. It quickly became the ubiquitous hedge plant we see all around us. In a tight hedge, and with limited biological diversity due to clonal reproduction by nurseries, its value to insects and birds is limited.

Another Arborvitae popular with builders is a hybrid called ‘Green Giant,’ which is a cross between a species indigenous to the Pacific Northwest and a Japanese species. As a hybrid between two non-natives, ‘Green Giant’ has very little value to insects or birds in this part of the country. If you can find the straight species of Thuja occidentalis (without a cultivar name), plant that. If not, ‘Emerald Green’ is a better choice than ‘Green Giant.’

Thuja occidentalis is an amazing tree. It deserves to be more than a fence! Given enough room to take its natural form, Arborvitae merits a starring role in suburban landscapes.

Growing the way nature intended, Arborvitae takes its
rightful place with Oaks, White Pines, and Junipers in
Northeastern landscapes

In our last blog post [Privacy Without “O-fence“], we urged homeowners to diversify their hedges and privacy screens by planting a mix of native trees and shrubs to increase habitat and biodiversity. Too much of any one plant becomes a mono-culture, limiting resources for wildlife. Unfortunately, that is what has happened to this magnificent native tree.

Don’t limit Arborvitae to this poor fate

Think of Arborvitae as an easy-care, long-lived, medium-sized, native, hardy evergreen that will enhance your landscape as part of a diverse planting of trees, shrubs, and perennials. You won’t be sorry!

THIS BLOG IS AUTHORED WEEKLY 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.

November 2, 2023September 17, 2025 Cathy Ludden Around the Grounds

Autumn Wonderland

The Northeastern United States is famous for fall foliage. “Leaf peepers” come from all over the world to see our native plants in their dramatic fall colors.

Why, then, should a walk around suburban neighborhoods, in the same region during the same season, be so disappointing? Where are the colors?

The plants that thrill “leaf peepers” grew in abundance before the suburbs were developed, and they would still thrive here – if only they were planted! It seems that every suburban yard uses the same non-native “foundation plants” — boxwood, pachysandra, ivy, and hedges of yew or privet or even bamboo! – all completely devoid of our famous fall colors!

C’mon people! We can do so much better than this! Why not plant our yards with the same trees, shrubs, and perennials that make this region a tourist attraction in the fall? Let’s add some color, life, and seasonal interest beyond pumpkins! There are so many great choices with our incredible abundance of Northeastern native plants.

Red maple (*Acer rubrum*)
Photo: Michael Martini

The undisputed rock-stars of fall color are our native Maples, and Oak trees are a close second. If you have a lawn, you probably have room for a Maple or a native Oak. Oaks have enormous value for wildlife — and for homeowners! [See this blog post] Both Maples and Oaks are beautiful year-round, but autumn is their glory season.

Our native flowering trees are also brilliant in the fall. Nothing beats the American Dogwood (Cornus florida) with its intense maroon foliage and vivid scarlet berries. Crabapples (Malus spp.) also produce colorful fruit, and American Witch Hazel (Hamamelis virginiana) starts blooming in October!

The Northeast is also blessed with native shrubs that produce kaleidoscopic colors in the fall. While evergreen foundation shrubs are useful, why not add some of the flowering and fruiting native shrubs that bring color and interest in both spring and fall? Here are some easy choices to add to your yard. All of the shrubs pictured below are locally available, easy to grow, valuable to wildlife, have beautiful flowers, and are spectacular in the fall.

Oakleaf Hydrangea (*Hydrangea quercifolia*)

Possumhaw Viburum (*Viburnum nudum*) pictured with
American Witch Hazel

Low Bush Blueberry (*Vaccinium angustifolium*)

American Cranberrybush (*Viburnum trilobum*)

And don’t forget fall flowers and grasses in gorgeous colors!

Aromatic Aster (*Symphyotrichum oblongifolium* ‘Raydon’s Favorite’)

Switch Grass (*Panicum virgatum* ‘Cheyenne Sky’) shown with Ironweed (*Vernonia lettermanii* ‘Iron Butterfly’)

Not only are these plants beautiful, they are incredibly valuable to the ecosystem of the Northeastern US. So many suburban landscapes use non-native plants that offer nothing to birds, butterflies, bees and other insects, and many are destructively invasive as well. If your only fall color is coming from burning bush or Japanese maple, you may want to consider native alternatives for those reasons. Privet, bamboo, ivy, vinca, and pachysandra are all known to be invasive plants and can be replaced easily with native plants that are beautiful in the fall, and year-round.

And wouldn’t you enjoy an autumn view like this?

Willow leaf oak (*Quercus phellos*), American dogwood,
and Pin Oaks

And this?

Oaks, Inkberry (Ilex glabra), Blue Star (Amsonia tabernaemontana and A. hubrichtii), High Bush Blueberry(Vaccinium corymbosum), Common juniper, and Possumhaw Viburnum

The fall glory of native plants lies within your reach!

THIS BLOG IS AUTHORED WEEKLY 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.

January 27, 2022February 14, 2025 Cathy Ludden Around the Grounds, Native Plants

Lookin’ Good, Leucothoe!

Leucothoe has a lot going for it:

It is a beautiful, flowering, evergreen, deer-resistant, low-maintenance, native shrub. It works very well as a foundation plant, groundcover, hedge, tree-underplanting, or pathway lining. With all these virtues, why is this excellent plant so under-used in our suburban landscapes?

Maybe it’s because nobody knows how to pronounce it? We’ve heard it said:

Lew-COE-tho-way, Lew-COE-tho-wee, and LEW-cuh-tho – and all those from experts! We favor the first choice, but if you’re shopping for it, the nursery staff likely will understand any of those options.

Or maybe Leucothoe suffers from the horrifying Greek myth behind the name? Poor Leucothoe was an innocent young woman whose father punished her, for entirely wrong reasons (look it up!), by burying her alive, whereupon she turned into a plant! Of course, it wasn’t this plant, because this plant is native to the Eastern US, and the ancient Greeks didn’t even know it existed.

Leucothoe in early summer with Christmas fern

Whatever the reason, Leucothoe definitely should be better known. There are actually two species of Leucothoe native to the East Coast. Leucothoe fontanesiana ranges from Louisiana to New York, while Leucothoe axillaris naturally appears only as far north as Delaware. It is not easy to tell the two species apart, and there are cultivars with fancy leaf colors derived from both. We see Leucothoe axillaris sold here frequently as Coast or Coastal Leucothoe. Leucothoe fontanesiana tends to grow a little taller, so read the nursery tag to see what the grower indicates for size.

So why should you know this plant? Leucothoe is beautiful, with gracefully arching stems and shiny, evergreen leaves. It is easy to grow, and incredibly useful. It typically grows about 3 feet high, and slowly spreads wider. It is naturally an understory plant, so it is happiest in shade, but will live in sun if it has enough moisture. Leucothoe is perfect as an evergreen ground cover, especially near wooded areas where pachysandra or ivy would pose an invasive threat. It will retain moisture and suppress weeds, so you can use it instead of mulch around trees or shrubs.

Leucothoe in winter as an evergreen ground cover

Leucothoe evolved growing in the relatively mild winters of Southeastern forests. It is a Zone 5 to 7 plant, so it should be protected from the coldest winter wind. You can use it as a foundation plant on the shady side of the house and not worry about having to prune it for size. It can drape over a stone wall or define the edge of a garden path. Pro tip: although sold in nursery pots with instructions to plant in a hole the same depth as the pot, we find Leucothoe likes to have its roots spread out wide and shallow, which makes it easier to plant around established trees and shrubs, too.

Leucothoe is great under trees and larger shrubs

Leucothoe flowers in late spring with little white bells that look like lily-of-the-valley, though the leaves hide the flowers to some extent. New leaves emerge in red or bronze shades before turning deep green. In winter, the shiny green leaves are very welcome.

Leucothoe survives heavy deer predation in a local park

Did we mention deer-resistant? We have found Leucothoe thriving in the woods in winter in areas known to be major deer hang-outs. And on our grounds at the Nature Center, Leucothoe is the only native woodland plant that really holds its own against the invasion of English ivy.

On the forest floor, Leucothoe fights back against invasive ivy and burning bush

So, consider Leucothoe as a native substitute for English ivy, Japanese pachysandra, vinca, or wintercreeper – all known to be seriously invasive if they reach wooded areas. Leucothoe forms a shiny, dark green skirt for the base of trees, leggy shrubs, or fences. It looks good all winter, and will still be looking good when the daffodils bloom in spring.

This blog is authored weekly 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.

January 13, 2022February 14, 2025 Cathy Ludden Around the Grounds, Native Plants

Winter’s Green

Recently in Around the Grounds, we featured native shrubs that add splashes of color to the winter landscape. (Read our Winterberry and Red Osier Dogwood posts here.) While brilliant berries and colorful bark are important for winter interest, evergreen shrubs are the backbone of the garden, providing structure throughout the year. And, as we remind ourselves, green is a color, too!

Unfortunately, our suburban landscapes tend to use a very limited repertoire of evergreen plants. We think there are better and more interesting choices than boxwood and taxus for residential foundation plantings. Take a look at some of the evergreens we’ve used at the Nature Center:

Inkberry shrubs define the edge of our patio garden all year

One of our favorites is the native Inkberry (Ilex glabra). Inkberry resembles boxwood, with similar dark green, shiny leaves. And, like boxwood, it can be pruned into a hedge, or a sphere, or any shape Edward Scissorhands might fancy. We prefer to let it take a natural, rounded shape with dense branches as hiding places for songbirds.

Inkberry looks similar to boxwood or Japanese holly, but is hardier

Unlike boxwood, Inkberry is adapted to our climate because it is native here. Boxwood originated in southern Europe, northern Africa, and western Asia; all climates very different from ours. Gardeners here are advised to wrap boxwood with burlap in winter to protect it from cold, wind, and salt – not a great look for “winter interest.”

Unlike Inkberry, boxwood needs protection from winter weather

Inkberry is not only cold-tolerant, even to temps below zero, but it enjoys our acidic soil and doesn’t mind sitting in water after heavy rainfalls. It is deer-resistant and salt-tolerant. It does prefer full sun, but can handle some shade. The straight species will get 6 to 8 feet tall, but it can be sheared and shorter cultivars are available.

We’re not sure why so many suburban dwellers like plants pruned into ball shapes, but we do know a native evergreen that will take that shape without any help! Growers have developed cultivars of our native Arborvitae that grow naturally into a ball shape without pruning.

Globe Arborvitae grows in a spherical shape

Arborvitae (Thuja occidentalis), also known as Eastern or Northern White Cedar, is very familiar as a tree; often used as a hedge or screen. It is native to our region and has wildlife value as a nesting site and seed supply for birds. Be advised that it is also famously attractive to deer. Some sellers of Globe Arborvitae claim the shrub is more deer-resistant than the tree, but we planted it close to a busy patio just in case. There are numerous cultivars of Globe Arborvitae available, with varying maximum sizes and slight color variations. Because we always prefer native plants, we would choose this little shrub over either boxwood or taxus – and we don’t have to prune it!

On our patio, Globe Arborvitae echos the rounded form of Inkberry

Another delightful evergreen shrub developed from a native tree is Pinus strobus ‘Soft Touch’ or Dwarf Eastern White Pine. ‘Soft Touch’ makes a great foundation plant. It is slow-growing, eventually taking a flattened shape no more than 2 feet tall, and wider than it is tall. It stays a lovely bright green all winter long. Its needles really are soft to the touch, and it’s hard to resist giving it a pat every now and then.

Dwarf White Pine ‘Soft Touch’ at the Manor House foundation

At the entrance to the Nature Center, we use another dwarf evergreen as a container plant. Dwarf Alberta Spruce (Picea glauca ‘Conica’) also was developed from a very large native tree, the White Spruce. This dwarf variety is very slow-growing and maintains its classic Christmas tree shape without pruning. It can live for years in containers, but should eventually be given some space in the landscape. It can become a 10-13 foot tree in time, so we will have to turn ours loose on the grounds in a few more years.