invasives Archives - Nature Center at Greenburgh

March 14, 2024February 12, 2025 Cathy Ludden Around the Grounds, Native Plants

What NOT to Plant

Spring is approaching! Garden and seed catalogues are arriving in the mail. Nurseries and big box stores will soon begin displaying thousands of plants for our home gardens.

As we plan to beautify our yards, it’s easy to be seduced by photos of gorgeous flowers and promises of carefree shrubs. But beware: many of these plants are not as advertised! It pays for avoid common mistakes now to prevent later problems that can cost you dearly.

The biggest mistake, both for nature and your wallet, is buying invasive plants. And it’s too easy to do! Many of the most common and familiar yard plants are actually invasive species. And most of them are still being sold across the country every day!

Garden catalogue offering an invasive shrub actually prohibited in several states.

English ivy costs American homeowners millions of dollars in tree and building damage every year, but is still sold legally in every state but Oregon.

The term “invasive” applies to plants from other continents that have no natural controls in North America (nothing here eats them!), and they are so successful at reproducing themselves that they spread unchecked causing environmental and economic harm. Invasive plants cost the US – individual property owners, corporations, non-profits, and all levels of government combined – an estimated $142 billion annually! Because invasive plants out-compete native plants, they take over forests, grasslands, wetlands, roadsides, parks, and residential areas, eliminating food and other resources for wildlife, as well as pulling down power lines, trees, fences, and damaging building siding and exterior finishes. Fighting invasive plants is frustrating and very expensive.

IMG_2762-3 — Invasive vines choke native trees on America’s roadsides.

IMG_2801-1 — Invasive landscape plants like Japanese pachysandra take over parks and wooded areas and are difficult to remove.

There are at least 5000 plant species currently identified as invasive in the US, and over 2/3 of them were introduced to this continent not for food, medicine, or commercial value, but simply because somebody thought they made pretty garden plants. Many states, including New York, have begun to regulate the sale or marketing of a few species of invasive plants. But the power of the nursery industry, and the popularity of many invasive plants with gardeners, has prevented more effective legal controls. Nurseries and mail-order houses still sell hundreds of invasive species. In fact, the nursery industry is the primary pathway for invasive plant introduction. Ultimately, though, it’s up to homeowners and gardeners to refuse to buy these plants.

So, how do we know which plants are invasive and should be avoided?

The simplest way is to use your phone! Put the name of the plant you’re considering and the word “invasive” into Google, or whatever search engine you use, and see what happens! For example, this is the result of a .32-second search using the words “pachysandra” and “invasive”:

Seeing that result should suggest choosing a different groundcover – a native one, perhaps?

Another way to avoid invasive plants is to watch for certain buzzwords in the ads. Like most businesses, the nursery industry grabs consumer attention with ads emphasizing the benefits of a product while omitting any discussion of the down-side. As you browse catalogues and nursery labels, watch for the red flags that signal invasive plant characteristics. Words like “grows anywhere,” “fast-spreading,” and “pest free” can mean that a plant has no natural insect or animal controls on this continent.

Catalogue offer using almost all the buzzwords.

This is a great example: any plant that will grow on “steep slopes, poor soil, trouble areas, stream or pond banks,” yet is “drought resistant and sub-zero hardy,” as well as “disease and insect free” and “grows so thick it chokes out even persistent weeds and requires no mowing or care” is the very definition of an invasive species!!

A quick Google search instantly turns up the truth about the advertised plant:

A search for “crown vetch invasive” immediately hits Invasive.org and state governments reporting the invasive plant.

At the bottom of the catalogue ad for crown vetch, there is a note that it cannot be shipped to certain states. That is another dead give-away. If any state has actually prohibited importation of the plant, it is extremely likely that the plant is invasive in many other areas as well. The political process just hasn’t progressed far enough to actually outlaw the plant in other states. Checking Invasive.org will tell the true story:

Invasive.org is a joint project of the University of Georgia and the US Department of Agriculture. They collect, review, monitor, and aggregate reports of invasive plant species that have escaped cultivation and infested natural areas. If a plant is reported as invasive anywhere in the US, it is best simply to avoid it and choose something else, preferably a native plant.

Of course, the best reason to avoid planting invasive species is to protect natural areas and critical habitat for American wildlife. But protecting the value of your own property, and sparing yourself the misery of trying to get rid of a plant you wish you had never planted, is another good reason.

If you fell for an ad like this:

Catalogue ad for *Aegopodium*, also known as bishop’s weed, or goutweed.

and then watched in horror as that “snowy” plant turned into a solid green mass, invading your lawn and every flower bed, you understand the meaning of regret. (We hear there is a “support group” on Facebook for people who have been victimized by goutweed!)

Other commonly sold plants that can become big regrets on suburban properties include: bamboo, Chinese wisteria, wintercreeper, Asian honeysuckle, periwinkle (vinca), Chinese silver grass, Rose of Sharon, ajuga (bugleweed), Norway maple, and of course, all forms of ivy. All of these plants can spread themselves well beyond where you wanted them and are tough to remove, creating maintenance headaches.

Still other invasive species may not cause trouble in your yard, but will find their way into nearby woods, parks, and natural areas: burning bush, privet, Japanese barberry, autumn olive, buckthorn, Bradford pear, tree of heaven, and Japanese spirea all spread themselves aggressively from gardens into natural areas.

There are so many excellent native alternatives to these troublemakers. Native plants do have natural controls! Birds, bees, insects, and other animals not only need native plants, their participation in the ecosystem will save you the expense and effort of battling invasive plants. Look back through the Around the Grounds Collection for lots of native plant recommendations that will work in your yard.

Happy spring gardening!

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.

November 15, 2023February 12, 2025 Cathy Ludden Around the Grounds, Invasives, Native Plants, Pollinators

Privacy Without “O-fence”

Suburban yards are places for families and friends to relax, perhaps enjoy a barbecue, and watch children and pets play safely. Privacy is important.

No wonder, then, that suburban homeowners often decide to plant a “privacy screen.” Hedges of trees or shrubs, planted as living “green fences,” are as common in suburbia as the lawns they typically surround.

But too often, these hedges are made with invasive plants that spread themselves into natural areas causing ecological harm. Top offenders include privet, Japanese barberry, forsythia, bamboo, and burning bush. All of these plants are recognized as invasive species and should be avoided.

Forsythia is not a good choice for a privacy screen

Burning Bush — Burning bush may look good for a minute

Japanese barberry, now banned in several states, spreads by seed into vacant lots, woods, and roadsides and actually increases the population of ticks carrying Lyme disease!

The good news is that the need for privacy does not require bringing any of these offensive plants onto your property. There are so many better choices!

In the Eastern US, the most popular privacy screen by far is Arborvitae (Thuja occidentalis), also known as Northern White-cedar. Favored by builders and landscape maintenance companies, a row of inexpensive and readily available Arborvitae is often planted along the property line as soon as a new house is built.

Though Arborvitae is a much better choice than any of the invasive plants mentioned above, it is not the only — or best — option. In areas populated by deer, Arborvitae is extremely vulnerable.

Here are some alternatives – beautiful evergreen trees and shrubs, native to the Northeast, that make ideal privacy screens. And because they are native, they also offer value to native birds and pollinators!

American Holly (Ilex opaca) makes a dense, evergreen privacy screen and has the bonus of tiny flowers for pollinators in the spring and beautiful berries that add winter interest to the landscape.

American Holly may be pruned into a hedge

Rhododendron is another good choice for privacy. When European settlers first explored the Eastern US, they struggled through massive stands of Rhododendron maximum that formed impenetrable evergreen thickets. Why not use that same feature now as an effective screen? Our native songbirds love to hide in a thicket!

Inkberry (Ilex glauca), another native evergreen, grows quickly and has shiny, dark green leaves that form a dense screen. More winter-hardy than boxwood and growing taller, Inkberry is a great hedge plant.

Red Twig Dogwood and Switch Grass — Inkberry in a mixed border with Red Twig Dogwood and Switch
Grass

The very best privacy screen, though, is not a row of one species of plant, but a forest! The Northeastern US was once predominantly forest, and many of the plants in those forests are still the best plants to grow here. In suburban yards, we can mimic the beauty, seclusion, and peaceful quiet of a diverse forest simply by planting more stuff! And a bigger variety of that stuff is inspired by our native forests!

Maybe it’s time to reconsider our approach to the “privacy screen.”

Hedges can be great, but they can also be visually boring and ecologically sterile. There is no law requiring homeowners to mark their property boundaries with a row of identical plants. Just because your property line forms a rectangle doesn’t mean your landscape has to be one. A diverse mix of plants – native trees, shrubs, grasses, and perennials – planted in masses makes a landscape interesting, lush, ecologically valuable, and very private.

Contrasting approaches – the mixed border of deciduous and evergreen trees on the right offers more interest, and more privacy, than the hedge on the left

white pine, arborvitae, spruce, juniper, and Rhododendron — A mix of White Pine, Arborvitae, Spruce, Juniper, and
Rhododendron completely screens a house from the road

If you already have a hedge or a fence along the property line, consider planting inside it using a mix of native trees and shrubs that change with the seasons. Start with the corners.

Trained landscape designers tend to avoid square corners and straight lines in their designed plantings. You can do the same thing. Map out curved beds that soften the corners and bring more plants further into your yard. Plant taller shrubs at the back, and choose flowering shrubs and perennials to plant in the foreground where you can enjoy them.

Fences along two neighboring properties meet to form a hard corner that is softened, and completely screened, by a curved planting of mixed trees, shrubs, and perennials

So, consider creating a privacy screen that looks more like a forest than a fence. By planting more plants, and a bigger variety of plants in more of your yard, you will have more privacy, more seasonal interest, less lawn to tend, and more habitat for birds, butterflies, and fireflies.

How’s that for a win-win-win-win?!

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.

October 26, 2023February 14, 2025 Cathy Ludden Around the Grounds, Invasives

Halloween Horrors!

Scary Invasive Vines

Ghosts, skeletons, and zombies! It’s Halloween, and our neighborhood is overrun by scary creatures playing trick-or-treat.

But look carefully. The most terrifying monsters in our neighborhood are the ones strangling our trees! Invasive vines are real-life ‘serial killers’ — stealing food, water, and light from trees, and leaving ghosts, skeletons, and zombies behind.

You’ve seen these vines doing their evil deeds. Our roadsides are infested with them. Our woods are being devoured by them. They cause trees to fall onto roads and buildings, costing taxpayers, utilities, highway departments, parks, and private property owners billions of dollars in property damage, clean-up, and removal. Even worse, in forests, meadows, and wetlands, these vines are replacing the native plants essential to maintaining biodiversity –the insects, birds, and animals in our ecosystem.

Three of the most destructive vines in our region are Oriental Bittersweet, Porcelain Berry, and the ever-popular English Ivy.

**Oriental Bittersweet (*Celastrus orbiculatus*)**

**Porcelain Berry (*Ampelopsis glanduosa*)**

**English, Irish, or Persian Ivy (*Hedera spp.*)**

All of these vines belong on other continents. They are invasive here because they have no natural controls in North America and, therefore, are able to aggressively out-compete our native plants.

So, how did they get here?

Gardeners! All of these killer vines were imported and planted here intentionally because gardeners found them attractive. European colonists introduced English Ivy as early as 1727. Oriental Bittersweet was introduced as a garden plant in the 1860’s, and Porcelain Berry was brought to the US from East Asia as an ornamental ground cover in the 1870’s. These plants had no commercial use or food value for humans or animals — they were planted solely for decoration. To be fair, gardeners back then had no idea what horror they were unleashing on the Eastern US. But we can learn from their mistakes.

Oriental Bittersweet is invasive from Maine to North Carolina and west to Wisconsin and Missouri. It is fast-growing and easily overwhelms native vegetation, both on the ground and in the tree canopy. Its enormous vines, up to 4 inches in diameter, can strangle, and even uproot, mature trees and shrubs.

**Oriental Bittersweet vine choking a tree**

Porcelain Berry is invasive from New England to Virginia and west to Wisconsin and Iowa. It is extremely aggressive on roadsides and other disturbed areas, as well as along forest edges. It runs along power lines, and often brings them down in storms. Porcelain Berry kills by completely enclosing shrubs and trees, stealing all available light, until the smothered plant dies.

**A young spruce tree struggles under a mound of Porcelain Berry**

**It’s too late to save these trees and shrubs from Porcelain Berry**

Ivy is a serious problem for us at the Nature Center, and we have warned about its dangers in earlier posts. See Evil Ivy Over Everything here. Where Ivy has escaped gardens in the US, it has destroyed vast areas of woodlands, reducing vibrant and diverse local ecologies to monocultures with no value at all for birds, insects, or forest animals. In suburban landscapes, Ivy causes enormous damage to trees, fences, and wood siding.

So, what have we learned from these gardening mistakes? According to the National Park Service, of the 1200 invasive plant species currently documented in natural areas, almost two-thirds were intentionally imported and planted as ornamental plants. Until recently, all three of these killer vines were still being sold and planted in gardens. In 2015, Oriental Bittersweet and Porcelain Berry finally were recognized as threats to the environment, and legally prohibited for sale and distribution in New York and a number of other states. English Ivy, however, has somehow been given a pass, and is still legally sold in every state except Oregon. Unfortunately, hundreds of other ornamental plant species, already known to be invasive, are still being sold and planted by gardeners all over the US. Legal regulation of invasive plants lags way behind the science.

So, what can we do to help? First, remove and destroy these three killer vines wherever you can, and be sure that the vines and berries go into the trash – not into brush piles or compost where they can easily spread further.

Next, before buying or planting any ornamental plant, do a quick investigation. It’s easy! Enter the name of the plant you’re considering into Google, or another search engine, along with the word “native” to quickly find out where the species originated. Plants native to your region are safe and beneficial to the ecology.

If the plant you are considering is not native to your region, do the search again, adding the word “invasive” along with the plant name. Websites devoted to preventing the spread of invasive plants will come up in your search and warn you if a plant is a known threat to our environment. Here is a sample search for the common landscape plant, Burning Bush.

Collectively, home gardeners have a huge impact on the environment. The most obvious example of their power – for good and for ill – is the horror of almost 1000 invasive ornamental species damaging our ecosystem. Our gardening forebearers made some terrible mistakes and unleashed these scary monsters on us. We can do better.

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.

October 27, 2022February 13, 2025 Cathy Ludden Around the Grounds, Invasives

Boo!

Ghosts, skeletons, and zombies! It’s Halloween, and our neighborhood is overrun by scary creatures playing trick-or-treat.

Three of the most destructive vines in our region are Oriental Bittersweet, Porcelain Berry, and the ever-popular English Ivy.

All of these vines belong on other continents. They are invasive here because they have no natural controls in North America and, therefore, are able to aggressively out-compete our native plants.

So, how did they get here?

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 17, 2022February 14, 2025 Cathy Ludden Around the Grounds, Invasives

Evil Ivy Over Everything

We have a big problem at the Nature Center. And we are not alone.

Ivy (Hedera spp.) – English Ivy, Irish Ivy, Persian Ivy – causes enormous damage to trees, buildings, and forest ecology throughout the United States. Maybe you’ve already seen Ivy pull stucco, mortar, trellises, and rain gutters off of buildings, or cause wooden siding to rot or attract mold. At least those things can be repaired.

The damage Ivy causes in nature is much worse. It climbs trees, slowly strangling them to death by stealing light and water, and it weighs down their weakened branches until they break and fall during storms. It crawls across the ground, sending out roots to take up all available nutrition. And it smothers the ground with its evergreen leaves so other plants cannot establish or find enough light to survive.

Ivy chokes trees by stealing light, air, and water

The weight of ivy breaks trees already weakened by choking vines

Forests in our region were once populated with hundreds of different species of shade-loving plants: ferns, grasses, and a huge variety of wildflowers. Those plants fed thousands of species of insects, birds, and animals. Of course, development and too many deer have contributed to a tragic loss of these species, and so has the introduction of invasive plants. Ivy is one of the worst offenders.

A healthy forest is filled with great diversity of plants

Ivy eliminates other species on the forest floor

There is nothing wrong with English Ivy — in England! It doesn’t overrun woodlands in Europe because it evolved there, and European insects and animals eat Ivy and control its growth.

In America, there are no natural controls, no insects or other animals to keep it in check, so Ivy becomes invasive. It out-competes native plants, leaving the forest depleted and sterile. Nothing here eats Ivy, so when Ivy is all that is left in the forest, there is nothing for forest animals to eat.

Some birds eat berries produced by Ivy and scatter the seeds, which can spread Ivy from garden to forest. But humans are much more culpable. Ivy is unfortunately popular with humans because it is evergreen, grows very fast, will live in sun or shade, and can cover a lot of ground or a wall very quickly. But it is also very difficult to control once it is established. Cutting vines at the base, applying herbicide to cut stems, and digging out roots can help save trees, but diligence is required to prevent this very aggressive pest from trying again.

There is no true Ivy native to North America. But there is a beautiful native plant that makes a great substitute for Ivy. If you want a climbing vine to cover a wall or an arbor, or you’re looking for a groundcover for a shady area, try Virginia Creeper (Parthenocissus quinquefolia). It is fast growing, and it has glorious fall color. Its leaves are the host plant for the very interesting Sphinx moth – the native insect that acts as a natural control preventing this vine from taking over the forest. Virginia Creeper will wind its way up a tree trunk, but it won’t kill your trees.

Virginia creeper evolved here, and belongs in our woods – *photo courtesy of pixabay.com*

Don’t be confused by the common names of Boston Ivy (Parthenocissus tricuspidata) and Poison Ivy (Toxicodendron radicans). Boston ivy is not from Boston and it’s not an Ivy. It is an Asian vine in the same family as Virginia Creeper. Though it is not as destructive as Ivy, it actually can grow faster and taller than Ivy and completely cover a building in no time. Poison Ivy is not an Ivy either. It is a native vine and, interestingly, it is only “poison” to allergic humans and not at all to other animals. It actually has a lot of wildlife value to birds and other animals. If it’s not in your immediate area, you could consider admiring its beautiful fall color from afar!

In the coming years, the Nature Center has a fight on its hands. We want to remove Ivy from our 33 acres of woods. While some areas are only partially affected, and we work hard to keep Ivy off of our trees, there are large sections of our forest totally overrun with Ivy. We will be formulating plans for an Ivy-removal program this year, but it will be difficult and expensive. If you would like to help by making a contribution, please visit our Donate page here.