Blog - Page 20 of 22 - Nature Center at Greenburgh

December 30, 2021February 14, 2025 Cathy Ludden Around the Grounds, Native Plants

‘Tis the Season to be Holly

Holly has been associated with winter holidays since long before Christmas celebrations began. It is thought that ancient Romans decorated with holly for Saturnalia, the winter feast in honor of Saturn. Druids and Celts believed the plant had magical powers because while all other trees lost their leaves, the holly not only stayed green, but displayed brilliant red berries in the darkest days of winter. So, holly branches have been cut and used for winter decorations for thousands of years. Our seasonal color scheme of red and green no doubt originated with holly.

Midwinter sunlight catches American holly near the Meadow

How fortunate that European settlers in the American colonies found a new species of their favorite winter plant growing here! American holly (Ilex opaca) differs from European holly in subtle ways and it can be difficult to tell them apart. The leaves of the American holly are not as shiny as the European variety, and the berries are often single rather than in clusters.

American holly trees typically grow 15 to 40 feet tall and 8 to 15 feet wide, but they can reach 60 feet where they are happy. They prefer well-drained, moist, acidic soil, and full sun for best berry production. Like other hollies, they are dioecious with male and female flowers on separate plants. For best fruiting, a male tree should be within 50 feet or so of the female.

An American holly tree in the suburban landscape

American holly is well-adapted to our area, of course, because it evolved here over thousands of years. It is less vulnerable to winter winds than many of the European varieties and it enjoys our acidic soil. It is a care-free evergreen and makes an effective year-round privacy screen. In a mixed evergreen border with Rhododendron maximum, White pine, and native junipers, it is not only attractive, but provides food and safe nesting habitat for birds.

A native mixed evergreen border with American holly

And when the winter holidays are here? What better combo than White pine, Winterberry, and American holly for the cheeriest “winter interest” in the neighborhood?

American holly, Winterberry, and White pine at the entrance to the Meadow at the Nature Center

We think that’s just jolly!

This blog is authored weekly by Cathy Ludden, local expert and advocate for native plants; and Board Member, Greenburgh Nature Center. Follow Cathy on Instagram for more photos and gardening tips @cathyludden.

December 24, 2021February 14, 2025 Cathy Ludden Around the Grounds, Native Plants

Deck the Halls…and Gardens

Every landscape needs “winter interest,” and several of our favorite native shrubs are real show-offs this time of year.

Without a doubt, the star of the season is Winterberry (Ilex verticillata). Winterberry is a holly, but unlike most hollies, it is deciduous – meaning it loses its leaves in the fall. And that’s a good thing! The berries start turning red in October while the leaves are still green. Weeks later, the leaves drop off revealing brilliant clusters of berries that remain all winter.

Or, at least, the berries could remain all winter unless the local birds have other ideas. We assumed for a long time that the berries needed all winter to ripen, because neither rain nor snow nor dark of night caused them to disappear until robins returned in the spring.

But in some years, mockingbirds, blue jays, and cardinals seem to celebrate the holidays with Winterberry snacks. So, we can’t totally promise the berries will remain all winter. But the robins definitely will finish up whatever is left in the spring.

If you have a boggy area on your property, Winterberry is a great choice – it will live in standing water and will happily send out shoots to form a thicket. So, it’s a great choice for a rain garden or a problem wet area. It does well in average garden soil as well, with full sun and regular moisture, and can be controlled easily by removing new shoots.

Like other hollies, Winterberry is dioecious, meaning both male and female plants are necessary for berry production. Bees visit the flowers on the male plant and carry the pollen to the flowers on the female plants to fertilize the ova and produce berries. Your local nursery will sell you a male shrub to plant somewhere near the female so bees can find both plants when they bloom in the spring. The flowers are small and white and not very noticeable, but the shrub is a lovely deep green all summer long.

Winterberry can grow 8 to 12 feet tall, but can be pruned for shape and size. There are cultivars that naturally stay much smaller – ‘Red Sprite’ takes a rounded shape and stays 3 to 4 feet tall. You’ll need ‘Jim Dandy,’ the male pollinating plant, to get berries on ‘Red Sprite.’ We suggest avoiding the recently-introduced Asian hybrids of Winterberry. The value of their berries for native birds and the risk of them becoming invasive are unknown.

Full-sized Winterberry in front of the Manor House at the Nature Center

‘Red Sprite’ is a compact form of the native shrub

This time of year, you may find whole branches of Winterberry mysteriously disappearing when it’s time to decorate for the holidays. The Garden Club of Irvington recently collected Winterberry and other foraged materials from our grounds to decorate the Nature Center. The impact of Winterberry on our fireplace mantles is spectacular! (Word of caution: the berries can be toxic to dogs, cats, and toddlers, so it’s best to keep them out of reach.)

A member of the Garden Club of Irvington decorates the Manor House mantel

Deck the halls with boughs of Winterberry

Winter solstice is nigh, and the Winterberry is bright!

December 16, 2021February 14, 2025 Cathy Ludden Around the Grounds, Pollinators

How Can We Help?

News of threats to butterflies, bees, and song-birds is everywhere. We hear that pesticides, climate change, and habitat loss are contributing to shocking declines in bird and insect populations, especially bees needed to fertilize food crops. Scientists report that insects are disappearing. We notice that moths don’t hang around our porch lights anymore, and bugs don’t splatter our car windshields as they once did. We may notice that bird species we often saw as kids are no longer around. We worry about what is happening, but we assume the solutions are beyond our individual control.

“The Insect Apocalypse”
New York Times Magazine, December 2, 2018

The good news is we can make a big difference right in our own back yards! Simple changes in the way we maintain our property – especially in the fall – can have an amazing benefit to birds, butterflies, and bees. We just have to understand what they need and make it available. Birds and insects need food and shelter all year long. Too many of our yards offer neither.

Many of us enjoy seeing winter visitors at our bird-feeders. But birds are vulnerable if they don’t have nearby places to hide. Planting densely with native trees and shrubs, and letting them take their natural shapes, provides shelter and much safer habitat than trimming too tightly to make trees and shrubs artificially neat. Birds need insects they find in holes and crevices in the bark of trees and shrubs, even in winter. So we need to have lots of trees and shrubs all around us, not just up against the house.

Birds need places to hide from weather and predators

Our flower beds and pollinator gardens can be valuable all winter long, too. There are more nutritious seed varieties in native flowers and grasses than in commercial bird seed mixes, so we should leave flower beds uncut until spring.

Most of our native bees over-winter in the ground. Shredded bark mulch prevents burrowing bees from finding the safety they need. Other bee species nest in hollow plant stems. By leaving flower stalks standing through the winter, we can provide habitat for many bee species. At the Nature Center, we have a “bee hotel” to demonstrate that nesting behavior. But it’s easier and far more effective just to leave the stalks of flowers and grasses up all winter long for nest sites.

Artificial native bee winter habitat – note occupied rooms!

Natural winter habitat – uncut flower beds!

Beetles make holes in old tree stumps or fallen logs that are later used by cavity-nesting bees for winter. Brush piles provide winter cover for birds as well as nest sites for bees, butterfly larvae, firefly larvae, and loads of beneficial insects.

Find an out-of-the-way place and stack a winter brush pile

It’s actually easier to create essential habitat for birds and beneficial insects than to strip your yard of all the good stuff in the fall. So, don’t remove your leaves. Don’t over-prune your shrubs. Don’t cut back your flowers and grasses. Don’t bundle up your twigs and branches and put them at the curb. Relax a little instead! There will be time in the spring, after everybody has left their winter beds, to tidy up for the new season. Let’s move toward a more natural look for our winter landscapes and a better environment for the creatures sharing it with us.

We really believe that’s beautiful.

For more information on the value of keeping fall leaves on your property, see our December 2 post here.

December 9, 2021February 14, 2025 Cathy Ludden Around the Grounds, Native Plants

Season of the Witch-hazel

We were very excited at the Nature Center last week to discover a beautiful Witch-hazel (Hamemelis virginiana) — in full bloom!

It was “discovered” when Guy Pardee of Suburban Natives, LLC freed it from a thicket of invasive shrubs and vines that had hidden it from view. Guy has been working for the past few years removing invasive plants on our grounds. Since restoring native plant life on our 33-acre preserve is one of our top priorities, it is especially gratifying to find a wonderful native tree right at its peak.

Witch-hazel is a fascinating plant. It’s a multi-trunked shrub or small tree that evolved as an understory plant in the forests of the Northeast. You might not notice it at all in the spring or summer when it modestly sits under bigger trees in part shade. But in early winter, when all the leaves are down and most plants are going to sleep, Witch-hazel starts blooming. Its flowers are fragrant, and bright yellow with tiny streamers reaching out in all directions.

The leaves, bark, and twigs of Witch-hazel contain tannins and flavonoids that Native Americans used for centuries to treat skin ailments. European colonists soon adopted the practice, and today Witch-hazel is one of the few plants the Food and Drug Administration has approved for use in over-the-counter products. Many cosmetics companies use Witch-hazel in toners, diaper rash remedies, acne treatments, pore reducers, and after-shaves.

Blooming Witch-hazel stands out against an evergreen background

A more questionable early use of Witch-hazel was the practice of using forked branches as dowsing or divining rods to search for underground water. A “water witch” would hold the forked end of a Witch-hazel branch and walk until the flexible tip supposedly dipped when underground water was detected. Dowsing with Witch-hazel branches for well-digging was a common practice right into the 20^th century.

The real mystery of this plant still isn’t settled. Why does Witch-hazel start blooming in winter when pollinators are already hibernating? And what insect does pollinate the flowers? Some researchers have pointed to a moth species that survives freezing temperatures by shivering so hard that its body warms above surrounding air temperature. Others have suggested that a small and very late-acting bee is the pollinator. Still others have theorized that swarms of tiny gnats do the job. More research is required.

But the coolest thing about this fascinating plant? Because of its strangely late pollination, there isn’t time for the fruit to ripen in the same year the flowers open. It takes the whole next summer for the seeds to slowly ripen in their pod. Then, just as the flowers start blooming in the freezing cold, the pod explodes throwing the ripe seeds 10 to 20 feet away, where hopefully they will rest until spring weather is warm enough for germination.

Lately, we’ve seen nurseries offering non-native hybrids of Witch-hazel for sale. These varieties with orange or red flowers are recent introductions of hybridized Asian species, so their value to our native wildlife and potential for invasiveness are unknown. Our view is that it’s always safer to go with species that evolved in our region.

Hamemelis virginiana, our native Witch-hazel, is a garden-worthy plant that brings late-season interest to suburban landscapes. Try it against a background of evergreens in a partly shaded area. On a cold winter’s day, you won’t be sorry.

Native Witch hazel brings winter interest to the garden

December 1, 2021February 14, 2025 Cathy Ludden Around the Grounds, Invasives

Turning Over an Old Leaf

As we learn more about the critical relationships between plants, insects, and birds, the best advice we are getting about fall leaf clean-up is … don’t!

In the old days, suburbanites taking care of their lawns raked (yes, raked!) fall leaves into giant piles to be burned. The familiar scent of burning leaves was everywhere – and we released tons of carbon sequestered in those leaves into the atmosphere.

So anti-burning ordinances were passed, and we started using gas leaf blowers to form the leaf piles, or bagging leaves for municipal workers to collect – all at taxpayer expense. Municipalities started spending millions to ship leaves out of the county. Enterprising souls then turned our leaves into compost to sell back to us. Not a good deal for us.

Bagged leaves to be collected at taxpayer expense

Leaves at the curb clog storm drains, a municipal headache

Since that routine makes neither economic nor ecological sense, we started hearing campaigns urging us to use mulching mowers. The idea was to chop leaves into tiny pieces and leave them on the lawn to enrich the soil. That method is a big improvement, and it definitely works — it’s great for lawn health and municipal budgets.

But we have learned that chopping up leaves has an unanticipated cost. Native bees burrow into the ground under leaf litter to survive the winter. Eggs and larvae of butterflies, moths, fireflies, and many other insects hang on to leaves, or hide under them, until warm weather returns. If we chop up or remove leaves to clear the ground in our yards, we are unintentionally destroying insects that baby birds need for food in the spring, as well as insects we need and enjoy.

Many insects need fall leaf litter to survive winter

Mourning cloak butterfly emerging in March at the Nature Center

The best use of fall leaves – and the best place for them – is under the trees that dropped them. Trees and all other forest plants evolved growing with a thick layer of leaves in the winter. Dead leaves nourish the soil and everything that lives in it. Leaf litter on your shrub and flower beds protects the roots of your plants and protects early buds from freezing and loss of moisture.

Of course, you’ll want to blow (or better, rake!) leaves off of driveways and paths, and either mulch or clear leaves that fall on lawn. But the best place to put them is in your shrub and flower beds and under your trees. A loose, 6-inch deep layer of leaves will not hurt your shrubs and perennials – quite the opposite. If there are still too many leaves, create a leaf pile in an out-of-the-way area, or add leaves to a compost bin. In spring, once the weather is warm and insects have had a chance to emerge, you can mulch the remaining leaves and return them to the lawn or flower beds, or even put them out for removal with spring clean-up.

Use your leaves to protect trees, shrubs, and perennials

Pro tip: Less lawn and more garden makes leaf clean-up a cinch! If your trees are surrounded by garden beds rather than lawn, nature does the work for you!