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.
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.
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.
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.
When the sun rises high enough to warm Blue-eyed Grass (Sisyrinchium angustifolium), its violet-blue flowers open wide to soak up the rays. A passing rain shower or dark clouds, however, will cause this sun-worshipper to fold up tight and hide until the sun reappears. From early May through June, and occasionally even later, the flowers of Blue-eyed Grass welcome the sun like kids on spring break.
Blue-eyed Grass basking in the sunshine.
Flowers curled up tight waiting for the sun after a rain.
Despite its common name, Blue-eyed Grass is not a grass at all. It’s actually in the iris family. The leaves are blade-shaped, like miniaturized versions of the leaves of bearded iris. And the flowers emerge from slits in the sides of the leaves, as they do in other irises.
Flowers unfold from inside the leaves.
The plant is only 6 to 12 inches tall, and the flowers are less than an inch across with cheery yellow centers. The small flowers can create a big effect if they are grouped along a walkway or at the front of a garden. They are a great choice for rock gardens, and for lining the edge of a paved path where the soil tends to be thin, poor, and rocky. Blue-eyed grass actually prefers poor soil and will suffer in rich, organic soil. Regular moisture is ideal as long as the soil is well drained — so a path to the front door is the perfect spot!
Blue-eyed Grass along a front entry walk.
Blue-eyed Grass is native to most of Eastern North America, from Newfoundland to Minnesota and south to Texas and Florida. Its typical habitat is damp meadows or grassy riverside areas where there is moisture, but sandy or rocky soil that prevents water from settling around the growing crown or roots. Most growers advise against mulching around the plant’s crown to prevent rotting. As long as you avoid that, the plant is virtually care free.
Blue-eyed Grass continues looking good even after the bloom season ends. The grassy clumps blend well with other small perennials or ground covers and stay fresh through fall. Hardy in zones 3 to 9, the foliage is semi-evergreen except in the coldest zones, and it is does not seem to mind being buried by snow shoveled off of walkways.
The grass-like texture of Sisyrinchium looks great all year.
Blue-eyed Grass is increasingly popular with suburban gardeners, so it is fairly easy to find at nurseries. A cultivar called ‘Lucerne’ was developed in Switzerland by horticulturists working with the North American native plant. Its flowers are bit bigger and darker blue than the straight species (all of the photos above are of ‘Lucerne’). Blue-eyed Grass is not attractive to deer or other mammals, but it does attract pollinators, so it’s a great addition to pollinator gardens. And the seed pods are favored by cardinals, house finches, and other songbirds late in the season.
Individual plants of Blue-eyed Grass are not long-lived, but they do seed themselves near the mother plant, so colonies can continue indefinitely. If re-seeding is not desired, dead-heading the flowers after blooming will prevent that. In fact, the whole plant can be sheared in mid summer to keep it tidy after blooming. Blue-eyed Grass grows from a small rhizome, but will also spread itself by sending out off-sets from the roots of the parent plant. If older plants seem to bloom less than before, they can be divided by digging up the plant and carefully teasing apart the roots to create new plants as well as refreshing the old one.
Though Blue-eyed Grass can be grown fairly easily from seed, it will take a few years to bloom. Container specimens can be planted in spring or early fall to give the roots time to develop. Gallon-sized or larger container plants will put on a good show their first season.
Sisyrinchium angustifolium straight species in the Meadow at the Greenburgh Nature Center. Photo: Travis Brady
It’s a bit surprising that we don’t see this wonderful native plant more often in suburban yards. Instead of planting annuals that must be replaced every year, why not choose this native perennial for your front walk or along the edge of your patio?
If you do, blue skies will have Blue-eyed Grass shining for you!
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.
