Cathy Ludden, Author at Nature Center at Greenburgh

April 3, 2025April 3, 2025 Cathy Ludden Around the Grounds, Lawn Care

Wait! Hold Off on Your Spring Clean-Up!

A day or two of warm sunshine in early spring makes us all eager to clean up the mess left by winter. We are so ready for spring that we just can’t wait to make our yards neat and tidy.

But wait! Resist the urge! Leave the leaf blower in the garage a little longer. Don’t rake the leaves from under your trees and shrubs. Don’t cut down your ornamental grasses and perennials. And don’t turn over the soil in your flower beds just yet. If you can be a bit more patient, the pay-off is enormous!

A lot of important stuff is happening in your yard in early spring, and you really should let it happen undisturbed.

Beneath all those dead leaves, pine needles, and broken twigs littering our yards, the roots of landscape plants are just waking up. Winter debris actually protects roots and tender new growth, providing essential insulation during the transition from winter to spring. Exposing those roots to unpredictable cold snaps and icy winds is asking for trouble. In addition, leaving soil bare only encourages weeds to develop before landscape plants have a chance to leaf out and shade surrounding soil.

Early spring storms and freezing temps can harm exposed roots

And there are other important things happening under the mess. As the weather gets warmer, butterflies over-wintering in fallen leaves and plant debris begin to emerge. How tragic is it that the prettiest butterflies of early spring are being carted away by lawn crews or left to die in leaf bags at the curb?

Mourning Cloak butterflies survive the winter in brush piles and leaf litter. They emerge early, but only when temperatures are warm enough. Don’t lose them by cleaning up too soon!

Birds that have survived the winter, or arrived after long migrations, are desperately looking for food in the lean stretch between winter berries and summer insects. As weather warms, caterpillars and other insects hatch in leaf litter where birds scratch around to find them. Clearing those leaves away too early means loss of critical food for birds just when they need it most.

In early spring, a White-throated Sparrow hunts insects in leaf litter

Native bees and fireflies also nest over winter where leaf litter covers the top inch or two of soil. Removing the protective leaf cover too soon exposes them to the cold. Turning over the soil too early destroys the nests, causing the death of essential pollinators, as well as summer’s fireflies.

Firefly larvae spend the winter in topsoil protected from freezing by a cover of leaves

So, what is the right time to begin spring clean-up? There is legitimate debate in ecological gardening circles about this topic. One school of thought is to wait until temperatures are regularly in the 50’s, allowing most ground-dwelling insects to emerge. Others note that many species of valuable insects emerge much later in the season, and some insects that nest in the hollow stems of perennials may even need more than one season to complete their life-cycle. Those experts recommend leaving some portion of un-cut or partially cut flower stems standing from season to season, never cutting all of them to the ground. All experts agree that leaving as many fallen leaves, and as much undisturbed soil, as possible — for as long as possible — increases survival rates of insects and birds.

The best approach is to adopt different clean-up strategies for different habitats. If you have a wooded area, let the leaves stay there indefinitely. “The best place for leaves is under the tree they fell from,” according to Dr. Doug Tallamy. And if you can’t wait to blow or rake dead leaves from hardscape and lawn, simply move them to wooded areas and spread them under trees and shrubs to preserve all of their ecological value on your property. If there are just too many leaves to make that possible, find an area where you can pile leaves loosely until it’s time to compost them. And don’t worry about clearing old leaves away from perennials in wooded shade gardens. After all, native shade plants evolved growing in forests. They have no problem emerging through leaf litter when they’re ready.

Early native perennials, like Jacob’s Ladder, happily emerge through the winter leaf cover

If you have sunny areas where you’ve planted flowering perennials and ornamental grasses, always leave them standing over winter. Then, wait longer than you think you should before cutting them back in the spring. If you wait until mean temperatures are regularly at least 50 degrees, the roots of your plants will be protected from late cold snaps and heavy spring rains, and you will be giving songbirds a better chance to grab the last seeds and earliest emerging insects. Leave a few stems of each perennial, especially the hollow stems, cut a foot or two above ground level, for nesting bees at the end of summer. New growth will soon cover the bare cut stems.

Not yet! Wait a little longer to cut everything back.

If you find you have too much plant and leaf debris to keep in existing areas of your yard, don’t send it all away. Consider turning part of your lawn into an expanded planting area in the new season. Mark off a new garden bed, add an edger, and pile the plant debris there to smother lawn and enrich the soil for the trees, shrubs, or native perennials you want to add this summer. By the time you’re ready to plant, you’ll have a good head start preparing the new beds.

So, relax for a few more weeks each spring! Thumb through garden catalogues, scout the local native plant sales, and plan your new yard projects for the summer. If you use a professional landscape crew, save a few bucks and tell them to start later. Their work schedule doesn’t have to determine your garden schedule.

We’re all eager for spring. You’ll know it’s here when you start seeing bumblebees buzzing around and realize you haven’t needed a jacket to go outside for a whole week. That’s when spring clean-up season is finally here!

March 18, 2025March 18, 2025 Cathy Ludden Around the Grounds, Native Plants

The All-American Shamrock

Legend tells us that St. Patrick used a shamrock, with its three leaves on a single stem, to teach ancient Celtic peoples about the Christian trinity. There is no agreement among historians, theologians, or botanists, however, as to which specific plant is the legendary Irish shamrock.

Some believe St. Patrick’s shamrock was one of several species of clover (Trifolium spp.) native to Europe and Britain. Others claim that the true Irish shamrock is in the family Oxalis, perhaps due to a report from a 16^th Century Englishman who wrote that the Irish ate “shamrocks,” and plants in the Oxalis family were known to be edible. Adding to the confusion, the Irish word “seamróg” means “little clover.”

Today, in honor of St. Patrick’s Day, several Oxalis species are sold as shamrocks both here and in Europe, which just annoys those who insist the traditional shamrock is a clover. In 1988, someone conducted a public opinion poll in Ireland asking which plant is the true shamrock, and the results split among several plants, including two varieties of clover and at least one Oxalis, with no real majority view.

In any case, St. Patrick’s Day seems an appropriate time to nominate an American native plant as the New World shamrock. Yellow Wood Sorrel (Oxalis stricta) is sometimes called “sourgrass,” “pickle plant,” or adding to the general confusion, “lemon clover.” As a candidate for St. Patrick’s Day shamrock, Yellow Wood Sorrel certainly looks the part.

**Yellow Wood Sorrel in bloom***Photo: Ansel Oomen, Bugwood.org*

Yellow Wood Sorrel is useful, maybe even pretty if you look closely, and it is found absolutely everywhere. Yes, it is a weed! You’ve probably pulled it out of your lawn, your garden, your containers, your driveway or sidewalk — maybe without knowing or caring what it is.

Like many other weeds, Yellow Wood Sorrel grows in a wide variety of habitats – sun or shade, dry or wet, and rich or poor soil. Each of its 3 leaves has a fold down the middle. At dusk, the leaves close up and stay that way until warmed again by the sun.

The little yellow flowers have 5 petals and bloom from spring through late fall. The plant produces lots of seeds in capsules that stand upright above the foliage. When the seeds are ripe, the capsule explodes, throwing seeds up to 3 feet away!

*Oxalis stricta* leaves fold up at night like little pleated skirts
*Photo: Courtesy of Pixabay.com*

Yellow Wood Sorrel is edible, though in very large quantities it may be mildly toxic. You really should try clipping some tender leaves, or the little yellow flowers, and sprinkling them like micro-greens on top of salads, fish, or chicken. The taste is like lemon, sour and a bit bitter, but refreshing. Tender stems and leaves may be steeped in hot water (a handful of leaves per pint of water) to make a lemonade-type drink high in Vitamin C.

Bees, butterflies, and ants make use of the flowers of Yellow Wood Sorrel, and its long season of bloom means the flowers are available throughout the nectaring season. Perhaps we should be grateful that this weed provides some wildlife benefit by stubbornly popping up in even the most manicured suburban landscapes.

**Yellow Wood Sorrel is a small weedy plant that grows everywhere**
*Photo: T. Webster, USDA, Bugwood.org*

So, the next time you find yourself pulling Yellow Wood Sorrel from all the places it doesn’t belong, think of it as shamrock and then save a few leaves for your lunch. Sláinte!

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.

February 20, 2025February 20, 2025 Cathy Ludden Around the Grounds, Native Plants

American Evergreen: Think Outside the Boxwood!

Evergreen landscape plants provide winter interest and year-round structure. Or, at least they should. But way too often, they totally fail at that function.

In general, suburban landscapes use too few species of evergreens, and often the wrong evergreens in unattractive ways. The same non-native shrubs — boxwood, taxus, privet, Asian azaleas and junipers – are repeated house-after-house, often clipped into shapes too strange to be natural and too tight to provide shelter for birds. Whether it is a failure on the part of developers and builders, or the nursery and landscape industry, or homeowners themselves, the result is dull, repetitious, and sterile landscapes. The over-use of non-native shrubs also sadly results in a lack of food and shelter for birds, insects, and other animals, all of whom depend on native plants.

But it is an easy fix! There are so many great native evergreens.

The last four blog posts in this series on American Evergreens featured Eastern Red-cedar, American junipers, Eastern White Pine, and American Rhododendrons, all excellent plants for suburban landscapes. But there are more! Browse through the posts linked below for more photos and information about each of these evergreen options:

American Holly (Ilex opaca) is a magnificent tree that grows slowly, eventually reaching 40 feet tall. It provides a dramatic evergreen backdrop for flowering shrubs and is a dense, year-round privacy screen. Its foliage provides essential shelter and its berries are prime food for birds. Be sure to plant a smaller male holly in the area to assure a good show of berries all winter. Click here for more information.

American Holly in fall and winter landscape

Inkberry (Ilex glabra) is a great substitute for boxwood. It looks very much the same, but is better adapted to our climate and soil conditions in the Northeast, so it does not have to be coddled in burlap all winter to protect it from ice and salt. Cultivars like ‘Shamrock’ and ‘Compacta’ are slow-growing, smaller than the species, and suitable for smaller properties or as foundation plants. Inkberry may be pruned as easily as boxwood and used for hedges. Older shrubs can get leggy with age, so underplanting Inkberry with smaller shrubs or perennials is a great idea. For more information and photos, click here.

Inkberry, here in its natural shape, doesn’t need winter protection

Alberta Spruce (Picea glauca), a majestic large tree in the wild, is more commonly seen as a dwarf cultivar ‘Conica’ that is very slow growing and attractive as an evergreen foundation plant, or even in a patio container. It is Christmas-tree-shaped and can provide a formal, vertical element in the garden. More info here.

Alberta Spruce, in front of Inkberry, provides a backdrop for bright Crabapple fruit in winter

Globe Arborvitae (Thuja occidentalis) is an alternative to tightly-clipped boxwoods for homeowners who prefer that spherical look. Rather than watering and fertilizing non-native shrubs only to shear off the new growth every year, naturally globe-shaped cultivars of our native Arborvitae are a better idea. Cultivars named ‘Hetz Midget,’ ‘Tater Tot, ‘Little Giant,’ and ‘Golden Globe’ require no fuss to hold their shape, and may provide better ecological resources than boxwood topiaries. More info here.

Globe Arborvitae at 5 years, never pruned, with natural-form Inkberries in the background

*Thuja occidentalis* ‘Hetz Midget,’ summer and winter, doesn’t need pruning or wrapping

Leucothoe (Leucothoe fontanesiana or L. axillaris), sometimes called “Doghobble,” is a fabulous understory shrub that should be used much more often. As a substitute for invasive pachysandra or ivy in a shady wooded area, it is without equal. It is low-growing, maxing out at 2 to 3 feet tall and spreading out gradually 3 to 4 feet wide. It is beautiful, foolproof, very deer resistant, and reliably evergreen. Plant it under trees, along fences, and in shady parts of your yard where deer are usually a problem. For a full description and more photos, click here.

Leucothoe and Rhododendron in a woodland garden

With all of these choices, suburban gardeners can add so much diversity to their yards! Native shrubs enrich the environment while adding beauty and variety to the landscape.

So, don’t stick with the same-old, same-old that you see around the neighborhood! This spring, plant more shrubs! Expand your tree and shrub plantings out into your yard, and update your foundation plantings with native shrubs.

Make next winter more interesting. Try American Evergreens!

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.

February 7, 2025February 7, 2025 Cathy Ludden Around the Grounds, Native Plants

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 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.

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

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.

January 24, 2025January 24, 2025 Cathy Ludden Around the Grounds, Native Plants

American Evergreen: Revisiting the White Pine

Eastern White Pine (Pinus strobus) is a magnificent tree that once dominated the North American landscape in the east from Newfoundland to Georgia and farther west from Ontario to Arkansas. One of the tallest trees in North America, it can reach well over 100 feet in height and live for hundreds of years. Its long, soft needles give it a somewhat fuzzy appearance at a distance, and with age, it takes on an irregular flat-topped shape that is unmistakable.

The needles are fragrant, 2 to 5 inches long, and held in bundles of 5. Young pine cones are 4 to 8 inches long and green, turning brown as they mature. Older cones are often tipped with whitish sap and are quite ornamental.

White Pine needles with a mature pine cone

White Pine is incredibly important to wildlife. Over 200 species of caterpillars develop on the needles of White Pine, making it one of the most important sources of food for baby songbirds. Many other insects also depend upon the bark, buds, cones, or needles of White Pine, so dozens of species of birds hunt and nest on the trees year-round. The tops of large White Pines are favored nesting sites for hawks, owls, and bald eagles. Numerous small mammals feed on the seeds produced in the pine cones, but deer avoid White Pine altogether, unless they are near starvation.

White Pine is relatively fast-growing, adding 2 to 3 feet per year. It typically grows a straight trunk with rows of parallel branches in whorls around the trunk, adding a new row each year. As the tree ages, it tends to shed its lower branches, which makes it great for lumber, but not for a privacy screen!

Taller than most of the trees around them, White Pines often take the brunt of wind storms, causing heavy branches to fall. For that reason, planting White Pines too close to houses or other structures can be risky, especially as weather becomes more extreme. So, homeowners these days are being advised against planting White Pines.

But wait! Not all White Pines grow to be giant trees! There are over 100 modern cultivars of White Pine, and many of them are slow-growing, small-to-medium-sized trees and shrubs! You can easily find a beautiful White Pine – or several! — for your landscape.

An elegant planting of several White Pine cultivars with a
mature White Pine tree in the background

The word “cultivar” is short for “cultivated variety” and means that a plant has been propagated through human intervention to develop certain desirable features. In this case, the desirable feature is smaller size. Shrub-sized White Pines are a great choice for evergreen foundation plants in residential landscapes.

*Pinus strobus* ‘Soft Touch’ 3 years after planting

Pinus strobus ‘Soft Touch’ is a dwarf cultivar that reaches a maximum size of 3 feet tall and 3 to 4 feet wide over 20 years. It is a lovely pine-green all summer long and, like the big White Pines, will drop some of its needles in the spring before putting out new growth. It looks almost fluffy, and it really is soft to the touch! The pictured 10-year-old specimen has yet to produce pine cones, but ‘Soft Touch’ is reported to produce small green cones eventually. Slow growth even makes it suitable for containers without need for transplanting for many years. It requires almost no care. No pruning, average water amounts, and application of compost rather than fertilizer, have kept both of the pictured plants happy. Full sun is best for virtually all evergreens, and White Pine definitely prefers it.

‘Blue Shag’ is another dwarf cultivar with blue-green foliage and a rounded, mounding form. It will slowly reach 2 to 4 feet tall and 5 to 6 feet wide. Its needles are shorter and its growth somewhat denser than ‘Soft Touch,’ but it does just as well with just as little fuss.

One of the more interesting cultivars of White Pine is a medium-sized tree, 20 to 40 feet tall, with curling needles, Pinus strobus ‘Torulosa.’ Its unusual needles apparently inspired efforts to create a dwarf cultivar with the same look. One result is Pinus strobus ‘Mini Twists.’

‘Mini Twists’ is a dwarf tree that begins as a rounded, globular shrub when young, but matures into a broad pyramidal form up to 6 feet tall at maturity. It grows very slowly and can live up to 50 years, making it an interesting accent in a suburban landscape.

There is even a “weeping” cultivar of White Pine that is a “semi-dwarf” tree growing 6 to 15 feet tall with long, drooping branches that may touch the ground.

Each White Pine cultivar has its own characteristics, including preferred growing conditions, so read nursery tags and on-line information before selecting one of the many offered for sale.

While native plant advocates generally recommend planting straight species of native plants rather than cultivars, in some cases, cultivars are the only real option. White Pines are in that category. A species White Pine that will grow 80 feet tall may not be a viable choice for the average suburban lot. But a White Pine cultivar of manageable size is an excellent choice, and far superior to those delicate non-native shrubs that need burlap wrappings just to survive Northeastern winters.

So, go ahead! Check out the interesting White Pines that work best for your landscape and add winter interest and native habitat for our wildlife friends!

For more on White Pines and their incredible role in American history, see the blog post linked here.