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
Trillium
Native columbine

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!

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 16th 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.
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 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.
Cathy Ludden Around the Grounds, Native Plants

The Shape of Hydrangeas

It’s hydrangea season and they are everywhere! But where are the bees?

Have you noticed that bees happily buzz around some hydrangeas while ignoring others? The difference is striking with these two hydrangea shrubs seen blooming side-by-side:

What accounts for the difference?

You might reasonably guess that native hydrangeas would be more attractive to native bees than Asian varieties, because that is often the case with other plants. Insects in North America usually prefer the plants with which they co-evolved, so non-native species are much less useful to them. But in the video above, both shrubs are non-native hydrangea varieties. So, what’s the difference to the bees?

When it comes to hydrangeas, it’s the shape of the flower that matters – at least to bees! And since 25% of native bee species are in sharp population decline, we really must care about what’s important to bees.

Hydrangea flowers, properly called “panicles,” are typically one of three shapes: “mophead,” “lace-cap,” or “conical” (cone-shaped).

Mophead
Lace-cap
Conical

In nature, hydrangeas have either lace-cap or conical forms composed of many tiny fertile flowers accompanied by larger showy 4-petaled flowers that are sterile. The only purpose of the sterile flowers is to attract the attention of pollinators, directing them to the real flowers – the tiny ones loaded with pollen and nectar.

Large sterile flowers draw attention to the tiny fertile
flowers inside
Pollinators find nectar and pollen in the fertile flowers

For bees, the sterile flowers on hydrangeas are just advertising. For humans, the sterile flowers are the pretty part. So, for hundreds of years, humans have been manipulating hydrangeas with selective breeding and genetic modification to create panicles with more showy sterile flowers and fewer — or zero — fertile flowers. The heavily-modified hydrangeas are spectacular to human eyes, but useless to pollinators.

Some of the showiest mophead hydrangeas have no
fertile flowers at all, and produce no pollen or nectar

The intentional modification of hydrangea flowers has crossed continents and hydrangea species. Many of the most popular hydrangeas in gardens today are mophead versions developed from the Asian species, Hydrangea macrophylla, or big-leaf hydrangea. You recognize these as the big round flowers that are pink or blue depending on the acidity of the soil, but they are also available in white, pale green, hot pink, and other colors. In fact, there are countless varieties of heavily-modified Asian hydrangea species on the market, including the popular tree form “Pee Gee” and the enormous conical flowers of “Limelight,” both modifications of the Asian Hydrangea paniculata.

Native North American species have been similarly modified to create fancy flowers. Hydrangea arborescens, or Smooth Hydrangea, is native to forests from New York to Ohio, and south from Oklahoma to Georgia. In the wild, it has flat-topped clusters of tiny white fertile flowers with occasional mutations adding a few sterile flowers scattered around the outer ring.

Natural form of the native Hydrangea arborescens

To make its flowers more appealing to humans, growers selected the mutated flowers and modified them dramatically to increase their number and size, eventually eliminating the fertile flowers altogether. The result was a plant with enormous mophead flowers that they labelled ‘Annabelle’ hydrangea, and introduced to the American market in the 1960’s. Since then, many other named varieties (‘Snowball,’ ‘Incrediball,’ ‘Invincibelle,’ etc.) have been developed to appeal to gardeners. Unfortunately, these showy mophead forms offer nothing to bees because the fertile flowers have been manipulated out of existence.

‘Annabelle’ and other cultivars of Smooth Hydrangea
have made this native plant useless for bees.
Photo from nursery advertisement

Even our excellent native shrub, Oakleaf Hydrangea (Hydrangea quercifolia), has been targeted for flower modifications by growers. Oakleaf Hydrangea naturally has large conical flowers that emerge white and gradually turn pink. They are beautiful and loaded with fertile flowers that are an important source of nectar and pollen for bees. (For more information on Oakleaf Hydrangea, click here.)

Oakleaf Hydrangea is native to the Southeastern US,
but grows well in gardens throughout the mid-Atlantic region
Conical flowers of Oakleaf Hydrangea are beloved by bees

Apparently not satisfied with an already excellent and garden-worthy native plant, the nursery industry has introduced cultivars of Oakleaf Hydrangea with flowers so altered that they have no remaining value to bees.

A double-flowered version of native Oakleaf Hydrangea
has eliminated fertile flowers completely
Dense conical flowers with no interior fertile flowers on
this Asian hydrangea do not support bees

Open conical flowers with large clusters of fertile flowers inside, like natural Oakleaf Hydrangea flowers, are a feast for bumblebees and other pollinators. And lace-cap flowers, whether Asian or native, because they are formed with large clusters of fertile flowers in the center, attract many species of bees.

An Asian lace-cap hydrangea visited by bumblebees

In a recent 5-year trial at the Mt. Cuba Center in Delaware, 29 cultivars of the native Smooth Hydrangea, including 16 mophead and 13 lace-cap varieties, were evaluated for garden appeal and performance. https://mtcubacenter.org/lacecap-hydrangeas-take-top-marks/ Investigators also monitored each of the plants for pollinator visits, extrapolating the results over the growing season. They found that lace-cap flowers were visited by pollinators at 3½ times the rate of mophead flowers. Although they did not report on the duration of visits, they did observe that bees approached the mophead flowers, but apparently did not often find reason to stay.

So, if we care about bees, flower shape matters!

For gardeners who love hydrangeas and also care about bees, the best bet is to include lace-cap and open conical flower forms with plenty of fertile flowers in your garden. Native Oakleaf Hydrangeas in natural form and native Smooth Hydrangeas in lace-cap form (like ‘Haas’ Halo’) are widely available at nurseries. And if you love the bright colors and playful shapes of the Asian lace-caps, they are a much better choice than the mopheads.

Go ahead and enjoy your mophead hydrangeas – they are harmless and we all love them. But think about adding a few lace-caps or conical forms with lots of fertile flowers for our bee friends.

You’ll love them, too!

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.

Cathy Ludden Around the Grounds, Native Plants

Walk This Way…

A paved walkway to the front door is one of the most common features of suburban residential landscapes. And it’s important! It is a visitor’s first impression of your home and a major element of “curb appeal.” Landscape design professionals recommend planting your walkway to welcome visitors and visually direct them to the correct entrance while giving them something interesting and beautiful to see along the way.

A well-planted entry walk guides visitors to the front door.
The entry path to the Greenburgh Nature Center in spring.

But a paved walkway presents multiple challenges for landscaping. The process of paving, whether with stone, concrete, brick, or asphalt, often damages the adjacent soil, leaving it compacted, dry, and rocky with bits of concrete and masonry that can significantly alter soil pH and create poor planting conditions.

New construction of paved areas can leave depleted soil.

Paved surfaces are also warmer in summer and colder in winter than the surrounding soil. Pavement reflects summer heat onto adjacent areas and can hold that heat long after sunset. Frozen pavement, on the other hand, can be even colder than surrounding air and soil temperatures, and snow cleared from walkways often includes salt or ice-melting products damaging to plants. With these extremes, it can be challenging to find plants that will look good and survive year-round.

Understandably, many suburban homeowners opt for planting nothing at all along walkways.

The minimalist approach.

Others plant a row of annuals every summer only to watch them wither and die long before fall (New Guinea impatiens anyone?). Most annuals are tropical plants that evolved in the understory of rainforests. The harsh conditions along a paved entry path are a far cry from the rich, wet soil in the shady jungles of equatorial New Guinea!

So, what can you plant along an entry path that will survive tough conditions through summer and winter, and still come back strong in the spring?

Consider plants that evolved in regions with baking hot summers, freezing winters, poor hard packed soil, and weather that can alternate between drought and flood. America’s great prairies and dry meadows are the original habitats of a vast array of hardy native plants. With variations in annual rainfall, soil depth, tree cover, and elevation, an incredible variety of grasses, flowering plants, and hardy shrubs evolved in those challenging landscapes. These native plants are ideal for the conditions so often found on paths from sidewalks and driveways to front doors throughout suburban neighborhoods.

The bonus is that these plants also feed native bees and butterflies and need very little care. Many of them already have been featured in prior posts of this blog. Take a look at these plants as you consider re-designing your entry path, and follow the links below for more information and photos:

Blue-eyed Grass (Sisyrinchium angustifolium) is a
cheerful sight lining a sunny path.
Field Pussy-toes (Antennaria neglecta or A. plantaginifolia) is a grey-green ground cover with
adorable cat-paw flowers.
Prairie Dropseed (Sporobolus heterolepsis) is a small
ornamental grass with a soft look and a lovely scent.
Mountain Mint (Pycnanthemum muticum) grows about 2 ½ feet tall,
has flowers that last for months, and smells wonderful.

Yet another prairie plant that looks great along a path is Prairie Smoke (Geum trilflorum). Its nodding pink flowers turn into puffs that give it another common name, Old Man’s Whiskers. The foliage stays fresh all summer and turns a lovely burgundy in the fall. It is not bothered by snow cover in the winter or hot dry summers.

Prairie Smoke in stages of spring bloom.

Another reliable low-growing groundcover that can fill in along a path mixed with shrubs and taller perennials is Barren Strawberry (Waldsteinia fragaroides). Blooming with bright yellow buttercup-type flowers for weeks from spring into summer, and semi-evergreen through the winter, it spreads slowly and is exceptionally hardy.

Barren Strawberry (Waldsteinia fragaroides) in March.

The most attractive pathway gardens include a variety of native perennials, grasses, and shrubs to create four seasons of interest.

A mixed border makes a path interesting.

There are a number of tough native shrubs that mix beautifully with perennials to create a real garden on the way to your front door:

Shrubby St. John’s Wort (Hypericum frondosum, or H. prolificum, or the pictured H. kalmianum)
are similar species, but different sizes, and all bloom with bright yellow pom-poms
adored by bumblebees.

Another great shrub for the entry path is Shrubby Cinquefoil (Potentilla fruticosa). Its flowers may be bright yellow or nearly white, its foliage a soft gray/green, and it blooms all summer long, much to the delight of native pollinators.

An entry path with Potentilla in full bloom.

So, there are many beautiful options for designing a durable planted path to welcome visitors (and nature!) to your front door. Think about pushing your lawn away from the path and giving a bit more space to a native garden that says: “walk this way!”

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.