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Conservationists, ecologists, and this blog repeatedly urge gardeners to use more native plants. Native plants are essential to a healthy ecosystem because they are the first link in the food chain. Insects native to a particular region generally cannot eat plants from other regions, and insects are the primary food source for birds and many other animals. We know that insect and bird populations are declining rapidly, so we ask homeowners, residents, and property managers to replace lawn, which has no ecological value, with abundant plantings of native trees, shrubs, grasses, and perennials. 

But not everyone can do that. Gardening is not everyone’s hobby and, for many people, taking care of a lawn and a few shrubs is really all they can manage. So, what if you want to help save songbirds, butterflies, and fireflies, but transforming an entire landscape to native plants is not an option? 

In a recent interview, Dr. Douglas Tallamy, research scientist and best-selling author of several books about the interaction between native plants and insects, was asked whether there are any simple things that anyone with a yard can do to benefit insects and birds. He immediately responded, “Plant an oak tree.”

Planting a native oak tree — or saving one — may be the single most valuable thing you can do to support nature. Oak trees are “keystone” plants, which means they are essential to the survival of many other species. Without them, there would be a cascade of species extinctions.

The importance of oaks to our native birds is perhaps the most dramatic example. Virtually all songbirds need insects to feed their young. Baby birds cannot eat seeds or berries. They must have insects, especially caterpillars. Caterpillars, the larvae of moths and butterflies, are soft, easily digested, and loaded with the nutrition baby birds need. Dr. Tallamy’s research has shown that a pair of Black-capped Chickadees needs 7,000 to 9,000 caterpillars to raise a single clutch of 3 baby chicks to maturity. Chickadees are very small birds and, if there is enough food, they can raise 2 clutches of babies in a season — that’s a lot of caterpillars! All of our other backyard birds have the same needs. Adult birds spend all day finding and transporting thousands of caterpillars to their nests. And where is the best place to find all those caterpillars? On the leaves of native oak trees!

Oak trees are caterpillar factories. Over 500 species of moths and butterflies lay their eggs and hatch their caterpillars on native oak trees. By comparison, not one single species of North American moth or butterfly caterpillar can mature on the leaves of a Norway maple! In fact, none of the popular non-native trees typically planted in suburban yards help birds feed their babies. Japanese maples, crape myrtles, Korean dogwoods, Norway spruces, Callery pears, and Kwansan cherries are essentially “barren” – they do not support caterpillar populations or other insects of value to birds. 

Planting a native oak tree, or saving one from destruction, is an easy way to support biodiversity. There are over 90 species of oaks native to the US, and many of them are widely available, hardy, easy to care for, and very long-lived. In the Northeast, white oak, red oak, scarlet oak, burr oak, pin oak, and black oak are all good choices.

And you don’t need a big property to have a happy oak tree. Although an oak can reach 100 feet tall with a crown spread of 120 feet given a couple hundred years, planted in an average-sized lawn, 20 or 30 feet from house and pavement, an oak can live its long life without causing any problems. The roots of oak trees tend to run deeper than most trees, so they are less likely to buckle your driveway or sidewalk than many other species. And oaks make great specimen trees in lawn areas because they typically have a more open canopy than maples or other big shade trees. They allow enough sunlight through to permit lawn (or native groundcovers) to grow underneath.

Oaks do best in full sun, and average, well-drained soil. Young trees will need regular watering until their roots are well-established, but once established, oaks need very little care. Professional pruning in the first decade will assure healthy branching, but supplemental water and fertilizer is rarely needed. 

It is easy to add an oak tree to any landscape because the best practice is to start small. Transplanting a large oak can be expensive and problematic. Oaks devote most of their early life to developing the root system that will keep them healthy for several hundred years. Large specimens from nurseries have been severely root-pruned to make transplanting possible, but the loss of root structure also makes them more vulnerable to transplant shock. So, starting with a small tree, or even a sprouting acorn, is inexpensive and likely to produce the healthiest tree in the long run. In just a few years, a young sapling will catch up to a severely root-pruned specimen and surprise you with how fast it grows!

So, do this one thing. If transforming an entire landscape to native plants is not an option, consider planting a young oak tree. If you have a lawn, you already have a good spot for the most valuable keystone plant there is. 

Plant an oak tree!

For further information, read the fascinating book The Nature of Oaks by Douglas W. Tallamy

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Winter is a tough time for our beloved songbirds. Food and shelter are more difficult to find. Food is scarce because insects, the best source of nutrition, are in short supply; and shelter, from weather and predators, is harder to find when branches are bare. Too many suburban yards, with big expanses of lawn and too few trees and shrubs, make matters worse. In this season, perhaps even more than others, we can help.

Scientists tell us that our songbirds are disappearing due to loss of “habitat” – places where food and shelter are available. Our parks, forests, and nature preserves are not enough to maintain bird populations, and there is not enough undeveloped land remaining for them. More than 83% of all land in the US is now privately owned, and 40 million acres of it is planted in turf grass, which is useless for birds. As a result, since 1970, we have lost one-third of the total bird population in the US and Canada. And the biggest losses, more than 90%, are in the once “common” bird species that should be found in our backyards!

So, suburban yards are increasingly critical to bird survival. We can save birds just by landscaping our yards to provide food and shelter all year long. We can plant habitat!

Creating habitat is not difficult, and it is beautiful. Simply by planting more native trees and shrubs – lots more — and by leaving native leaves, grasses, and perennials in place all winter, we can provide a supply of food and shelter for birds while making our yards more interesting and attractive.

The bark of native trees – including oaks, birches, hickories, and white pines – hides over-wintering insects and becomes a hunting ground for many birds in winter. Chickadees, Nuthatches, and Woodpeckers all prowl tree bark looking for food.

The leaves that fall from native trees, especially oaks, hide seeds and insect larvae essential for birds’ winter survival. Allowing fallen leaves to remain under trees and on perennial beds all winter, rather than blowing and bagging them for disposal, provides a continuing food source for songbirds.

Native trees and shrubs with berries feed birds and add winter interest to the landscape. Winterberry, Common Juniper, and American Holly liven the garden with berries that birds love.

The simple decision to leave ornamental grasses and flower stalks standing all winter, rather than cutting them down, is an easy way to provide food for winter birds. The changing colors and shapes of the plants are beautiful over the season, and birds will be frequent visitors there.

Winter birds also need shelter – places to hide from predators and to huddle in freezing temperatures. Open lawn, with a few tightly clipped shrubs, offers no protection.

Instead, a yard heavily planted with trees, shrubs, perennials, and grasses is the place birds want to be. Evergreen trees and shrubs offer great hiding places. Rhododendron, Mountain Laurel, Leucothoe, Juniper, and Inkberry are beautiful evergreen shrubs birds will appreciate. Deciduous shrubs that form a thicket of dense, twiggy stems, even without leaves, protect songbirds from hungry hawks. Shrubby St. John’s Wort, Dwarf Fothergilla, Winterberry, Bayberry, Oakleaf Hydrangea, and Virginia Sweetspire are all good examples of native shrubs that provide both seeds and hiding places in winter.

Many of us try to help birds by setting up backyard feeders. But most birds won’t stay out in the open while they feed. They “grab and go.” If you want birds to frequent and benefit from your feeder, you’ll need trees and shrubs — a thicket – nearby where they can hide while they eat.

Planting habitat for birds in our own yards is no longer optional – it is urgent! We are running out of time. Bird counts in 2022 show that populations of more than half of all US bird species are continuing to decline. Birds are disappearing because they have nothing to eat and nowhere to hide. Suburban gardeners and homeowners can make a difference if we act now.

We must go from this:

To this:

A special thank you to Sav DeGiorgio, Arborist for the Parks and Recreation Department of the Town of Greenburgh, for his beautiful bird photographs! See more of Sav’s photography on Instagram: @savwildlifephotography

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.

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In the depths of winter, when the garden is mostly brown, the only thing better than a beautiful evergreen plant is one that is ever-blue!

Carex laxiculmus or Creeping Sedge is a low, clump-forming grass that stays blue all winter long. It is an excellent garden plant: durable, care free, deer resistant, and versatile. In its native habitat (moist woodlands in the Eastern US), Creeping Sedge is a slowly spreading ground cover in shady areas. It forms compact clumps with strappy blue-green leaves, about half an inch wide and a foot long. Once established, it sends out underground rhizomes that will pop up nearby to form new clumps. It is not very aggressive, and is easily controlled, but in a few years, it can form a lovely colony under trees and shrubs, or in a shady flower garden.

Carex laxiculmus is easy to find in nurseries under the name ‘Hobb’ or “Bunny Blue” sedge, a trademarked name. Growers Lisa and Bobby Head of South Carolina trademarked the cultivar and named it “Bunny Blue.” The trademarked plant differs little from the native species, and in 2019, Neil Barger of New Moon Nursery reported that in side-by-side trials at New Moon, there was little discernable difference; but if anything, the species seemed to perform slightly better than the trademarked cultivar. Others believe that “Bunny Blue” is somewhat bluer in color than the species and more tolerant of dry soil. Though at the Nature Center we prefer planting straight species whenever possible, “Bunny Blue” is much easier to find, and we love it!

Although it is native to moist woodlands with rich soil, we have seen “Bunny Blue” sedge perform well even in thin, fairly dry soil. It is a good choice for underplanting trees. A small plant can be tucked in among sensitive tree roots, and it will send rhizomes out to find open spaces without disturbing or competing heavily with the tree’s root structure. “Bunny Blue” sedge is hardy in Zones 4 to 7, but can take the heat even in Zone 9 with enough shade and supplemental water.

“Bunny Blue” sedge makes a great “living mulch” when combined with other native shade-loving plants. Plant it with native ferns, Wild Ginger (Asarum canadensis), Foamflower (Tiarella cordifolia), and violets to protect tree roots and preserve soil moisture while providing habitat and food for wildlife. Use it instead of hosta and liriope in shade gardens, and instead of pachysandra, ivy, vinca, or winter-creeper under trees and shrubs.

Carex laxiculmus flowers in early summer, but the flowers are barely noticeable on fine stems rising just above the grassy clump. The lush foliage works well in rain gardens, and the spreading rhizomes are effective at controlling erosion on slopes or rain-washed areas. The lovely blue color works even in shady patio containers for color contrast with summer annuals. Plant it in the garden when summer ends!

In late winter or early spring, you can cut back the foliage of “Bunny Blue” sedge to the base of the clump, or just snip off any tattered leaves. New growth will soon appear, adding a bit of blue to your otherwise green spring!

THIS BLOG IS AUTHORED WEEKLY BY CATHY LUDDEN, CONSERVATIONIST AND NATIVE PLANT EDUCATOR; AND BOARD MEMBER, GREENBURGH NATURE CENTER. FOLLOW CATHY ON INSTAGRAM FOR MORE PHOTOS AND GARDENING TIPS @CATHYLUDDEN.

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“Trees exhale for us so that we can inhale them to stay alive. 
Can we ever forget that?”

Munia Khan

Caring for our trees properly begins with understanding how they live. We can avoid harmful mistakes if we understand what a tree needs for healthy roots, bark, and leaves. Human-caused damage to tree roots and bark is often accidental. [see “For the Love of Trees” Part 1 and Part 2] Unfortunately, the most common damage humans do to the leaf canopy is intentional. 

The practice of “topping” a mature tree — cutting the trunk and major branches to an arbitrary height – was once thought to reduce the likelihood of “top-heavy” trees falling in storms. But topping is actually counter-productive and dangerous. The result is a weakened tree that is more likely to fail — and fall.

Topping a tree drastically changes its shape, and ignores the reason nature has shaped trees the way they are. Tree branches reach upward and outward, away from the trunk, dividing again and again, becoming smaller at every division as they extend to the outermost twigs holding leaves. The purpose of this shape is to provide the maximum exposure for the largest number of leaves to absorb sunlight coming from above.

Leaves need sunlight for photosynthesis — the miraculous process that turns sunshine, carbon dioxide, water, and soil into the oxygen we breathe. But oxygen is just a happy by-product of photosynthesis. The real purpose, as far as the tree is concerned, is to manufacture carbohydrates to feed the tree. Trees bring water and soil nutrients absorbed by the roots up through the living outer layers of the bark to the leaves. The carbohydrates manufactured by the leaves during photosynthesis are then carried back down to feed the living bark, including all the growing branches and twigs, and the roots. Topping is a brutal interruption of this process.

A healthy tree is balanced — both nutritionally and structurally. Nutrition is balanced because the root system absorbs just enough nutrients and water to supply the leaves, and the leaves manufacture enough carbohydrates to feed the growing trunk, branches, and roots. Structurally, the tree balances itself with a root system that grows strong and wide to anchor the heavy trunk and the weight of the leaf canopy. As the tree matures, the roots, trunk, and leaf canopy continue to grow in proportion to one another — and in balance.

Topping a tree, by removing most of its essential leaf canopy, suddenly and radically reduces the tree’s ability to manufacture enough nutrients to support its living trunk and root system.

A topped tree may begin putting out twiggy little branches, called “suckers” or “water sprouts” in an effort to quickly add more leaves. Even if leaves develop, however, the thin new branches are incapable of carrying enough nutrients back down to feed the mature tree trunk and roots. Deprived of the carbohydrates essential for survival, the roots farthest from the tree will wither and die, and the trunk will weaken, destabilizing the tree.

There is a very strong consensus among modern tree experts that topping is a bad practice. So why do we see so many examples of topped trees all around us?

While most responsible tree companies refuse to top trees, or at least try to talk property owners out of it, homeowners often insist on topping and look for a tree service that will comply. Reasons given for topping trees include fear of trees falling, a desire to open up views, to increase light for lawn or solar panels, or simply to make trees shorter. All of these may be good reasons for appropriate tree pruning, which is completely different from topping. It is important to understand the difference.

Trees should be pruned to remove dead, weak, diseased, or crossing branches that can damage bark. Pruning by experienced, certified arborists is part of responsible tree care. And a qualified arborist can address aesthetic issues as well as tree health. Selective pruning at branch nodes can lighten the canopy, allowing more light underneath and improving air circulation. Careful thinning can reduce excessive weight on particularly vulnerable branches, or reduce the reach of branches too near buildings or power lines. Strategic removal of a few branches can open a “window” to a desired view. Before deciding on any of these options, discuss your concerns with a qualified, experienced arborist to determine the wisest approach. Sometimes, removing a tree in the wrong place is the better choice. 

If your tree company suggests topping, or “hat-racking” or “topping off” or “lopping” or “rounding over,” call another tree company. Trees subjected to any of these versions of topping will never look right, even if they manage to survive.

If your tree company suggests “crown reduction” to reduce the size of a tree, proceed with caution, and only after a very thorough discussion of exactly what is intended. A well-pruned tree will look natural. Fewer than 20% of the existing branches will be pruned back, and you should not be able to tell where they were. A “crown reduction” job that cuts back all or most of the branches is just another version of topping.

Trees need their full complement of leaves to stay alive and to manufacture the very oxygen we breathe. Supporting them in that precious work is our responsibility.

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.

For more on tree care, read these posts:
For the Love of Trees : Part 1
For the Love of Trees: Part 2

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