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Invasive Species: Natural World Bullies

The Teal Trail near Westville is a horror show of invasive plant overgrowth. This picture from July 2017 is AFTER I spent four hours cutting back a quarter mile section of trail. Clearly much more work needs to be done. If invasive species are not targeted, over time the entire park could look like this. There is no new tree growth in this area because the saplings are choked off by the natives. Offenders include privet (a hedge from Europe), multi-flora rose (a sharp-thorned shrub), Asiatic bittersweet (a vine that twists around trees and strangles them), Japanese honeysuckle (a vine that creates a dense mat of vegetation), and winged euonymus (burning bush, a shrub with corky "wings").

Invasive Species at West Rock
Why should you care about invasive species in the woods? If you get annoyed at trails that are overgrown, particularly those with sharp thorns that tear at your clothes and flesh, then join me in the war against invasive plants. These are the plants that grow quickly and take over a trail within a hiking season.
New England woods should have a "clean" look to them with clearly defined plants of all sizes. If the woods look like a dense jungle with green things growing everywhere, you are probably seeing an area heavily impacted by invasive plants.
Invasive plants can be viewed as natural-world bullies, the kind of thugs that if they were human would be knocking you down and stealing your lunch money.
West Rock has its share of problems caused by these non-native, non-desirable species.
Briefly, an invasive is any animal or plant that is not native to an area, and was usually brought here by people who thought introducing such a species was a good idea. Most invasive plant species come from Asia and Europe.
Another reason to have an interest in removing invasive plants: visit the wildflower page on this website and imagine that page as a memorial to plants that no longer exist at the park. Fortunately, that is not the case, but it could happen if the invasives are allowed to spread.

This page is not a comprehensive list of invasive species, nor it is a complete list of invasive species at West Rock, only a list of the most common and widespread invasives.
How seriously does Connecticut take this issue? Seriously enough that is against the law to import, move, sell, purchase, transplant, cultivate or distribute these species discussed on this page: the Asiatic bittersweet vine, the Japanese honeysuckle vine, multi-flora rose, autumn olive and Russian olive, and garlic mustard. Japanese barberry and winged euonymus are common landscape plants sold in nurseries and garden centers.

This area adjacent to the Teal Trail near Westville, as seen in January 2015, shows the "messy" look created by invasive plant overgrowth as they overrun and choke out native and desirable plant species.
Invasive Plants
Invasive plants all share certain characteristics, which is why they are invasive. These plants tend to grow quickly, and grow in many habitats, crowding out native species. They often have leaves earlier in the spring and later in the fall than native species. They can create dense shade, which makes it difficult for native species to survive in their shadows. They are prolific seed producers, seeds which are spread by birds that eat them.

If you cut them, they grow back even faster. They are even resistant to chemical control. I do not mess with chemicals, so all of my methods are mechanical. Most invasives are found near the edge of the woods where there is more light and where the birds that spread them tend to congregate.

Some people have asked me, “What’s the point?” and “Are my efforts making a difference?” My belief is that we have already lost the war, but we can win battles, reclaim areas, and slow the spread of these invasives. In a worst-case scenario, there will few woods left if we do not control the invasives, as they will choke out the growth of new native trees and shrubs.

Another common question regarding invasives is "How did they get here?" In most cases, someone traveling to another country saw a plant they liked and brought back a sample for a home garden. Once removed from their native environment where the species grew in competition with others, and likely had natural predators to keep it in check, these plants can displace and outcompete native species.

The areas at West Rock most afflicted and overrun by invasives include the Red-White and Red Trail by Farm Brook Reservoir off Hill Street, the gravel road portion of the Red Trail south of this pond, the Teal Trail near Westville, the Red Trail along the Wintergreen Brook north of Lake Wintergreen, and Baldwin Drive.

The Red Trail north of Lake Wintergreen is nearly closed off by fast-growing plants in Aug., 2017, despite having been thoroughly pruned back in March 2017. Assorted invasive plants are responsible for most of the growth. I pruned this back in Sept. 2017, but did not take an "after" picture of that work.

If you are thinking of controlling invasive plants, my most important rule: Know what you are cutting! Well-meaning people can do far more damage than good if they mistakenly cut native shrubs thinking they are invasives. I tell people who help me, "I can always return and cut an invasive you missed. I can't replant something native that you cut."

The Nov.-Dec. 2015 issue of Connecticut Wildlife magazine (published by the Department of Energy and Environmental Protection) had an article called “Whip-poor-will Inventory and Monitoring 2010-15 Summary”, written by Shannon Kearney-McGee, DEEP Wildlife Division, that gives a specific example of how invasive plants negatively affect birds.
The article on page 15 talks about how the whip-poor-will bird is in severe decline in Connecticut due to various factors including development and invasive plant species. The article states, “Only one of the 11 locations (9%) that contained whip-poor-wills also contained invasive species, while 11 of 26 locations (42%) where whip-poor-wills were not detected contained invasive species. This is significant because invasive plants have been shown to produce fewer moths and butterflies than native plants. Moths and butterflies are an important food source for whip-poor-wills.” The full article may be read online at

Invasive Plants and Lyme Disease
The state of Connecticut has been studying Lyme Disease and has made a definitive connection between the presence of invasive Japanese barberry in the forest and the number of Lyme-disease carrying black legged (deer ticks). Essentially, barberry is the ideal habitat and breeding ground for these disease-carrying ticks. The more barberry in an area, the greater number of ticks: 120 ticks per acre in a barberry-infested forest vs. 10 ticks per acre in a barberry-free forest. I cannot think of a more compelling reason to control barberry.
Fortunately, West Rock does not have a significant barberry problem. There are isolated patches of it, but West Rock does not have the vast swaths of barberry that carpet some hiking areas.
In 2014, I helped out on an invasive clearing project at Sheffield Island, off the Norwalk coast, and spent an hour cutting up barberry in an off-trail area blanketed with the prickly stuff. I emerged from the area absolutely covered with ticks. Despite repeated checks and removing many crawling ones from my clothes and skin, I missed one and caught it as dropped off me a week later, fully engorged. I had it tested by the state and it was identified as a lone star tick, which does not carry Lyme Disease. If you go to Sheffield Island, stay on the gravel paths!
Another plant that has been linked to tick populations and therefore Lyme Disease is Amur Honeysuckle, a shrub with flaky, tan-colored bark. Fortunately, I have seen almost none of this shrub at West Rock. By contrast, the boardwalk by Little Pond at White Memorial Conservation Center in Litchfield, and the accessible portion of the Appalachian Trail in northwestern Connecticut are lined with this shrub.
These are some good articles with more details about the barberry-tick-Lyme Disease connection:

The Connecticut Agricultural Experiment Station (CAES), which has been doing the research on this topic published a guide in February 2013 called Japanese Barberry Control Methods: Reference Guide for Foresters and Professional Woodland Managers, written by Jeffrey S. Ward, Chief Scientist for CAES; Scott C. Williams, Associate Scientist for CAES, and Thomas E. Worthley, Association Extension Professor, University of Connecticut. The guide presents an overview of the barberry-tick link and has detailed information about how to control it. This guide is very useful for homeowners as well.

Williams, Ward and Megan S. Linske published a research article on this topic entitled Long-Term Effects of Berberis thunbergii (Ranunculales: Berberidaceae) Management on Ixodes scapularis (Acari: Ixodidae) Abundance and Borrelia burgdorferi (Spirochaetales: Spirochaetaceae) Prevalence in Connecticut, USA available here:

The Rise of the Tick by Carl Zimmer, published in Outside magazine, April 30, 2013, is a an informative look at the work by these scientists in studying the barberry-tick connection. Website:

Controlling Japanese Barberry Helps Control Ticks by Sheila Foran in UConn Today, on Feb. 22, 2012, also describes the work of these scientists:

Managing Exposure to Ticks on Your Property, a guide written by Kirby C. Stafford III, Ph.D, chief entomologist for CAES, does not discuss barberry, but provides tips to create a property that is not favorable to deer and ticks. Website:

Invasive Shrub Increases Risk of Human Disease (via Ticks, Deer and Bacteria) is an article published Oct. 10, 2010 by Ed Yong on the National Geographic website, discussing the way amur honeysuckle creates a favorable habitat for ticks. Website:

Native blackberries ripen in Aug. 2017 on the Regicides Trail near the Purple-Orange Trail. Many blackberry plants grow along the Regicides Trail, but in other areas are displaced by thorny multi-flora rose, an undesirable invasive plant.

Invasive Plants vs. Natural Alternatives
These are lists of common invasives and West Rock and the preferred natural alternatives that are displaced by invasive plant species.
  • Oriental bittersweet and Japanese honeysuckle vines vs. Concord grape vines (You can eat grapes, but not bittersweet berries).
  • Autumn olive and Russian olive vs. witch hazel, spicebush, and winterberry (Witch hazel, spicebush, and winterberry are attractive shrubs that peacefully co-exist with other native plants).
  • Winged euonymus and privet vs. high-bush blueberry (You can eat blueberries, but not euonymus or privet berries).
  • Multi-flora rose vs. raspberry and blackberry
    (You can eat raspberries and blackberries).
  • Japanese barberry and Japanese knotweed vs. low-bush blueberry and huckleberry
    (You can eat blueberries and huckleberries).
  • Garlic mustard and mugwort vs. native wildflowers (Yes, you can eat garlic mustaard, but I prefer the native wildflowers).
  • Phragmites vs. cattails (Cattails are an important food source for animals, but phragmites have nothing to offer them.)

This tree was blazed in April 2012 on the Teal Trail, and in the two years that followed, the blaze became covered by a combination of invasive species: Asiatic bittersweet and Japanese honeysuckle vines, and the shrubs multi-flora rose, and privet.
This tree was temporarily liberated from its captors in Jan. 2015.
It died in 2017 and I cut it in pieces after it fell across the trail.

Asiatic Bittersweet Vine
Asiatic bittersweet gets my vote for the next most devastating species at West Rock. This species is easily distinguished by the fact that it wraps itself around trees and strangles them. Even before it strangles trees, its leaves will overgrow the canopy of the tree and shade out the leaves. In the winter, it has red berries hanging, waiting for birds to eat and spread them.
This picture taken in Jan. 2015 on the Teal Trail dramatically shows how a bittersweet vine wraps around one tree while it continues to grow toward another. Note the grooves in the bark where the tree continues to grow around the vine. Eventually the vine would strangle the tree, but I cut the vine, allowing the tree to survive.

Even more dramatic is this view of a bittersweet vine stretching across multiple trees along the Red Trail near Farm Brook Reservoir.
Multiple vines encircle a tree.

A close-up of one vine around that same tree.

A close-up of this small bittersweet vine shows its distinctive orange roots. Desirable and native Virginia creeper with its clusters of five leaves climbs the rocks in the background.
Feel free to take these berries for your winter arrangements. Just be sure to keep the arrangement inside, and dispose of them in your trash where they will head for the incinerator and certain death, and not in your yard, where you will further contribute to the spread of the problem.

In the woods, the Asiatic bittersweet creates a “messy” look as it hangs on trees, pulls them down, and leaves a jumbled pile of wood in its wake. They have a dark brown, smooth bark when young, and a beige-colored smooth bark when older. If you pull them out by the roots, the roots are orange.

Asiastic bittersweet is very different looking than the native grapevines and poison ivy. Grapevines have a dark brown flaky bark and they have distinctive “elbows” or bends in their stems. Grapevines will hang from the trees, but will not wrap themselves around the trunks. Poison ivy clings to one side of a tree trunk and has a “hairy” look that is caused by its external roots.

My method of dealing with bittersweet is to cut the vine as high as I can reach. At the ground, if the vine is not too big, I will pull out the roots as best I can. This method immediately removes the threat to the tree (if it is not already wrapped too tightly), and also diverts the plant’s energy from making seeds (and therefore more vines) to growing more vines. Since this does not kill it, I have to return in future years to continue to cut it. Larger vines I simply cut as high and low as I can.
More information at
Asiatic bittersweet hangs from a tree on Baldwin Drive at West Rock. The vines twine amongst themselves. I cut them after I took this picture.
This is a close-up of Asiatic bittersweet vines hanging from a tree on Baldwin Drive.
Asiatic bittersweet creates a wall of leaves as it hangs from trees on Baldwin Drive at West Rock, shading out the tree and other plants.
Another look at how Asiatic bittersweet hangs from a tree on Baldwin Drive at West Rock.

Japanese Honeysuckle Vine
Another invasive vine at West Rock is the Japanese honeysuckle vine. I have seen this in various locations along the Regicides Trail, particularly between the South Overlook and Judges Cave, and near a crossing of Baldwin Drive at the northern end of the park. This vine is also engulfing the Teal Trail and the Westville Feeder near Westville. Like Asiatic bittersweet, the honeysuckle wraps around a tree or shrub and strangles it over time.

When the honeysuckle vine is young, it resembles a brown thread. As it matures, it looks exactly like twine with regard to its tan color and rough texture from multiple strands. The honeysuckle will also keep its leaves year-round, unlike the bittersweet vine that drops it leaves in the fall.

The honeysuckle is harder to remove than bittersweet because the honeysuckle will spread widely along the ground and when pulled the smaller vines break, leaving the roots intact in the ground.
More information at
This close-up of a young Japanese honeysuckle vine in Dec. 2014 on the Westville Feeder Trail shows the thin, brown stems of the young plant and the fact that it retains its leaves in cold weather.
This is a wider view of the Japanese honeysuckle vine on the Westville Feeder  in Dec. 2014, showing how it envelops a hapless native shrub.

Multi-Flora Rose
Multi-flora rose gets my vote for the most obnoxious invasive. This shrub can grow to 15 feet tall, and have stems that dangle over trails, just waiting to catch an unsuspecting hiker. If you get caught in one, it can shred your skin as you try to escape.

They are tricky to cut back because of the way they grow. I find that I have to cut off the stems and work my way into the bush to reach the main part of the bush where I cut it at the base. Regrettably, this does not kill the bush, but it certainly does ruin its day.

There’s a stretch of the Red Trail heading north from Lake Wintergreen where I spent time in the winter cutting back multiple multi-flora rose bushes. When I returned in the spring, it looked as if I had planted the stuff, there were so many remaining. Still I believe in the importance of this work because over time they will completely choke out an area, making it impassable.
More information at

Multi-flora rose blooms along the Red Trail near Farm Brook Reservoir. While the flowers are pretty, the thorns are deadly, and this fast-growing plant displaces anything native.
Autumn Olive and Russian Olive
Autumn olive and Russian olive are an attractive shrub/small tree from Asia that grows to about 15 feet high. I have seen only autumn olive at West Rock and there are many examples of it. I have seen these shrubs with trunks as thick as 5 inches. They have a light-gray bark, thorn-like protrusions about an inch long, and grow a round berry about the size of a blueberry.

Autumn olive has a pale red berry and the Russian olive has a light green berry. Their branches grow at an angle from the trunks, so they lean in all directions. They keep their leaves until past the first frost, so they get an extra month of growth. They shade out other species, particularly the native mountain laurel.

When I cut these down, I am amazed by how much more light gets into the forest. The state hired a contractor in winter 2008-09 to cut back the autumn olive in fields by the Lake Wintergreen parking area, and off the gravel road by Mountain Road that leads to Farm Brook Reservoir (the fishing pond off Hill Street). The contractor chemically treated the stumps, and the state mows these fields annually, so the autumn olive has not regrown. However, autumn olive is spreading through the woods by the gravel road portion of the Red Trail near Farm Brook Reservoir.

Autumn olive along the Red Trail near Mountain Road, visible on the right as the green shrub. There is a patch of autumn olive I cut every year and every year, it resprouts. Over time I am making progress at holding down the spread of autumn olive in this area, since shrubs that put their energy into resprouting are not growing seed-producing berries.
There are extensive areas of autumn olive remaining near the water tank on the slope of the ridge (which the trails crew cut in April 2015 and April 2016 with help from Quinnipiac University students as part of the annual Big Event). The Regional Water Authority, which owns the land around the water tank, followed up and clear cut the area in front of the fence, along the Gold Trail. The vines are resprouting quickly in this clear area with plenty of sunlight.

There is much autumn olive on the Red Trail extending about 1/2 mile south of the northern section of Mountain Road. There is also plenty growing along Baldwin Drive, especially in the first mile extending from the main entrance. The fields by Farm Brook Reservoir are lined with autumn olive, although many were cut to create the Red Trail along the water. I continue to cut this autumn olive and cut the resprouted plants as I return to the area for additional work.

When I cut back autumn olive, I can return a month later to find multiple thin stems extending from the trunks, as it seeks to regrow. As with other invasives, by cutting it back, I have slowed its growth, interrupted its seed producing potential, and given native species a chance to grow. I have had good success in killing autumn olive through repeated cutting.

The autumn olive berries can be eaten, not that I have tried them, and can be made into a jam, not that I have tried that either, so feel free to pick as many as you like.

More information for Russian olive at
More information on autumn olive: and at
This is a cute video called "The Nightmare That Threatens Your Garden," using the theme of a black and white horror movie from the 1950s, then moves into an informative discussion of why autumn olive is a problem:

A large autumn olive shrub grows in all directions on Baldwin Drive at West Rock.
When cut, the shrub will vigorously resprout from the base.

This picture of autumn olive along the Red Trail near Farm Brook Reservoir
shows how vigorously this shrub resprouts when cut.

A medium-sized autumn olive shrub on Baldwin Drive at West Rock.
A close-up of the autumn olive leaves show
how they are lighter green on the bottom than on top.
Autumn olive has a pale flower in the spring.
Winged euonymus
I have found winged euonymus or burning bush at West Rock in the Judges Cave area, near the West Rock tunnel ventilation shaft, and along the northern part of the Regicides Trail They also grow in great number along portions of Baldwin Drive.
The greatest number seem to be along the lower portion of the Westville Feeder, despite a multi-year battle that has pulled up hundreds of them. This plant can create a carpet of other shrubs from the numerous seeds it produces. The smaller ones can easily be pulled out by the roots, leading to their certain demise.

There is a fairly extensive problem with this plant at the nearby Bishop Estate/Darling House Trails in Woodbridge and I can only hope it stays off the ridge.

This is a popular plant in landscaping, especially at shopping centers, because the leaves have a vibrant red color in the fall, and the plant itself is hard to kill. They are fairly easily recognized by the cork-like “wings” along the branches that give the plant its name.
More information at

Winged euonymus becomes a beautiful red color in the fall, plus it is a hardy shrub, which is why this is so popular in landscapes, particularly at shopping centers. The problem is that it outshades and outgrows native shrubs like blueberry.
This close-up of the winged euonymus shrub shows its cork-like "wings" along the stems. These "wings" are not always visible, especially on young shrubs.
This euonymus shrub grows in the leaf litter and dirt on Baldwin Drive. This photo shows its cork-like "wings" along the stems.
This close-up of the winged euonymus shrub on Baldwin Drive shows its cork-like "wings" along the stems. These "wings" are not always visible, especially on young shrubs.
A winged euonymus plant along the Sanford Feeder Trail. This plant outcompetes the native and desirable high bush blueberry plant, which also has red leaves in the fall.

Privet (European and Chinese)
Fans of Harry Potter recognize the name privet, which is the name of the street where the fictional English lad lives. Privet is a common hedge in the United States that can easily grow 20 feet tall. The oval shaped leaves of the European version are easily recognized. European privet also had small bluish-black berries in the fall and winter.

Privet is found at West Rock along the Teal Trail near Westville, at the top of the Red Trail by the South Overlook, along the Blue Trail near the pavilion, and in the woods behind Judges Cave by the Green Trail. I found a small patch on Baldwin Drive. I pull smaller shrubs and cut larger ones.

More information on European privet at and on Chinese privet at
Chinese privet flowers along Baldwin Drive, June 2014.

Chinese privet crowds the Red Trail by the South Overlook in June 2017.
The Red Trail by the South Overlook in June 2017 after the privet has been cut back.

Japanese Knotweed
This invasive is known as Godzilla weed in reference to its origins and the fact that it is impossible to kill. It looks like a short bamboo with distinctive rings every six inches. It has an attractive white flower in late summer. The spring shoots can be eaten like asparagus. I have not tried this, so I have no comment on the flavor.
On a positive note, some say that it can be used to treat Lyme Disease. I have no personal experience with knotweed as a Lyme remedy.

There is a patch of knotweed on Wintergreen Avenue, near the junction with Springside Avenue, across from the Brookside Apartments. This patch continues to spread north every year.

Japanese knotweed lines the forest edge along Wintergreen Avenue.
I have been fighting a patch of this on Baldwin Drive near the Orange Trail crossing. In summer 2014, I pulled it out three times, but each time the remaining patch was smaller. I returned in 2015, 2016, and 2017 to continue to pull out these plants. In 2017, I was pleased to see that native blackberry shrubs were growing and over time, I hope these will fill the area.

These two photos show a multi-phase project to remove Japanese knotweed along Baldwin Drive in summer 2014. The first photo shows all the plants I pulled in June 2014 and left along the road to dry. The second photo from July 2014 shows the dead plants from the first removal behind the plants that regrew, which I pulled out after taking the photo. I plan to continue to monitor this site to remove any other plants that regrow.

There is a large patch about 30 feet wide by 30 feet deep on Mountain Road, adjacent to a small parking lot near the Red Trail. From July to October 2016, it took me 14 hours worth of work over five visits to pull it and then pull it again when it resprouted. When I returned in November 2016, the patch was completely brown, but it resprouted in spring 2017. I returned with two helpers to dig it out by the roots. The patch resprouted again, but not as strongly, and I continue to fight the battle. I pulled as many as I could and cut the rest in Aug. 2017.
The technique I learned for this area is that knotweed has a root that is long in one direction (side to side), so if I pulled across the root, then I could fairly easily uproot it. When I dig it out, I use a pick mattock to pull out as much as I can.
In this area, I found a few raspberry plants, and grape vines that will hopefully spread with the knotweed removed from competition. Adjacent to the knotweed is some goldenrod and milkweed.
One concern is that the open field behind this knotweed patch is a vast sea of mugwort, which will seek to intrude into this area.

The weakness of knotweed is that its stem is fragile and easily cut. The challenge of knotweed, as compared to other invasives, is that it can regrow to full size within a growing season. By comparison, I can cut down a 15 foot tall autumn olive shrub with 3-inch diameter stems. When it reprouts, at the end of the season, the new shoots might be five feet tall with a quarter-inch diameter stems.
More information at
This website chronicles a fight against Japanese knotweed in Massachusetts: 

Japanese knotweed along Mountain Road in July 2016 before pulling.
The knotweed patch in July 2016 after two hours of pulling. Knotweed maze, anyone?

The Mountain Road knotweed patch in August 2016 after two visits.

I cleared the patch in August, and in September 2016, the patch aggressively resprouted, so I pulled it again.
The knotweed patch in September after it was pulled and partially resprouted and pulled again. A line of invasive mugwort can be seen at the back of this area.

In October 2016, the knotweed had resprouted, so I pulled it again.
The Mountain Road knotweed patch resprouted in May 2017.

The Mountain Road after being pulled and cut in May 2017. Near the street are daffodils planted by a neighbor. The patch continued to resprout through summer 2017 and was again cut back in Aug. 2017 (not pictured).

Japanese barberry
Barberry is less of a problem at West Rock than it is in other hiking areas where you can literally see barberry as far as the eye can see. At West Rock, I find isolated patches of this shrub that has thin, needle-like spines, shiny red oval berries, and distinctive bright yellow stems and roots. There are some extensive patches of barberry on adjacent water company land along the Sanford Feeder Trail.

This is an easy invasive to kill because it can be pulled up by the roots. When they are too large to pull up, I cut them. If there are berries on the plant, I collect them and put them in the trash to prevent even more barberry growth. 

Morrow's Honeysuckle or Bella Honeysuckle
Morrow's honeysuckle, also known as bella honeysuckle, is a shrub with oval leaves and rough, woody bark. In season, it has small red berries. I have seen this in scattered places at West Rock. On the handicap-accessible portion of the Appalachian Trail, Morrow's honeysuckle can be seen everywhere, completing taking over everything by the trail itself. Only through the efforts of volunteers is the trail being kept clear of this unwanted shrub. I have also seen this along the Mill River at East Rock Park.
There is more information on the New York Invasive Species Information website at and on the Southeastern Wisconsin Invasive Species Consortium at

Black Swallow wort
Invasive black swallow wort has been identified in two places at West Rock. There is a large section alongside the Regicides Trail over the West Rock Tunnel. There is another patch of it along the Regicides Trail, just north of the split with the Green Trail, shortly past Judges Cave. As this photo shows, it completely takes over an area.
More information on the plant is presented at this website:
This article "Invasive Vines Swallow Up New York's Natural Areas" calls this pale swallow wort, but the plant is the same:

Invasive black swallow wort has completely taken over the slope
over the West Rock Tunnel alongside the Regicides Trail.

Garlic Mustard
Garlic mustard is a ground-dwelling plant that is green year-round. It has a vaguely heart-shaped leaf with notched edges. One problem with garlic mustard is that it puts a chemical in the soil to inhibit the growth of other plants. This is small and numerous, so I have focused my efforts on the bigger invasives at West Rock.
I am told you can eat this in salads. I have never tried. Feel free to pick as much as you like.
More information at

Garlic mustard completely displaces other plants in the open field adjacent to the Hill Street parking lot, as seen in May 2015. The plant is easily uprooted and I pulled out some of these after taking this photo. They will grow again from all the seeds likely to be found in the soil.

Garlic mustard flowers in the field
adjacent to the Hill Street parking lot in May 2015.

Mugwort (artemisia vulgaris) is a reedy weed that grows about five feet high and will completely take over an area. It is readily pulled out and yields a distinctive spicy smell when pulled. It has uses in herbal medicine. I have found this on the Sanford Feeder Trail at the Regicides Trail where through repeated pulling, I have greatly reduced its number. It is also located on the Red Trail near the pond off Mountain Road, under the powerlines south of Mountain Road, and north of Lake Wintergreen.
Herbal information page, for which I am not qualified to endorse the information should you wish to try it:

Mugwort lines the Red Trail under the powerlines, just south of Mountain Rd., Aug. 2017.

Mugwort displays a faint green flower. Native grapevines with their large leaves grow behind the mugwort along the Red Trail under the powerlines, Aug. 2017.

Phragmites or Common Reed
Phragmites australis is a tall reed about 8 feet in height common seen in Connecticut wetlands and marshes, and along lakes and ponds. The reed has a distinctive "flag" of seeds at the top. It displaces native cattails because it is taller and its roots spread aggressively. Chemical control is the only viable solution, so I have not attempted to combat this invasive. There is phragmites along the dam at Lake Wintergreen, and in the marshy area north of the lake, both along the Red Trail. Regrettably, the plant is spreading north along the Red Trail.

This is a native species known by the scientific name of smilax bona-nox, but certainly NOT desirable along trails. I have gotten torn up by this plant that has distinctive green stem, with lethal sharp thorns. It grows up into trees as high as 30 feet. I have seen this along various trails at West Rock. The name catbrier refers to thorns as sharp as cat claws,while bullsbrier most likely relates to its ability to act as a natural fence for cattle. I cut this back along trails.
More info at:

Invasive Flowers

Some beautiful flowers at West Rock unfortunately are invasive. These are some I have photographed:

Sulfur Cinquefoil
This pale yellow flower is native to Europe and has a bitter taste that keeps native animals from eating it. Website:
Sulfur cinquefoil on the gravel road portion of the Red Trail
near Farm Brook Reservoir, Aug. 2015.
Crown vetch
Crown vetch is a legume with a flower that ranges in color from purple to pink to white. It grows in open fields and displaces native grasses and flowers. There are more aggressive invasive plants that demand a higher priority, so I leave this alone.  It is readily found at West Rock in the open field by the Hill Street parking lot, and near Farm Brook Reservoir. The state mows the field about once a year, so that helps control it. Information at and

Crown vetch grows in the field near the Hill Street parking lot, June 2015.
A close up of the crown vetch flower, June 2015.

Animal Invasive: Woolly Adelgid
Perhaps the biggest devastation at West Rock has been caused by an insect that you cannot even see called the woolly adelgid. This tiny creature sucks sap from the needles of the Eastern Hemlock tree, gradually killing the tree over a period of about five years. Somewhere in this story there is a metaphor about the mighty being felled by the tiny, as the woolly adelgid is too small to be seen without magnification, and hemlock trees can grow to 150 feet tall and live for 400 or more years.
The woolly adelgid is visible by the white egg sacs that give the insect its name. These egg sacs cling to the underside of the needles of infested trees. The adelgid has no predators in the United States, but does get eaten by a Japanese ladybug that the state has tested as a measure of biological control. Unfortunately, the ladybug is killed off by Connecticut winters, which are cold enough to slow the spread of the adelgid, but not cold enough for long enough to kill the pest. In a residential setting, the adelgid can be controlled by an oil or injection applied by a trained arborist. In the woods, there is no present and practical way of control.
The devastation at West Rock is most visible along the Regicides Trail where the trunks of felled hemlocks continue to lie alongside the trail. I can only imagine the shade they once provided along this ridgeline trail. A healthy hemlock is truly a magnificent tree with vibrant green needles that stretch from ground to crown. Unlike the white pine, hemlocks thrive in shade and keep all of their needles. White pines die in shaded areas and even in sunny areas, will gradually drop their needles on their lower branches as they are shaded by the upper branches.
An infected hemlock has a sickly greenish gray cast to its needles, no needles on the lower branches, and as the insect advances up the tree, fewer and fewer branches have needles. There are places in West Rock that still have isolated, healthy hemlocks, but they are few and far between.
These are links to two state reports on the woolly adelgid: "Controlling Adelgid and Scale Within Our Forests," by Dr. Mark S. McClure, a now retired state scientist for the Connecticut Agricultural Experiment Station (CAES), and a report by McClure that was revised by Carole A. Cheah, Richard S. Cowles, and Rose Hiskes of the CAES at The first report mentions that the woolly adelgid has difficulty surviving in temperatures below -5 degrees Fahrenheit, which is positive news after the frigid temperatures in February 2015.

This tall hemlock tree leans across the Regicides Trail in Aug. 2017 after being killed by the woolly adelgid. The Regicides Trail used to be lined with hemlock trees that created cool shade along the top of the ridge, but they have been mostly killed off by the invasive insect.

Animal Invasive: Emerald Ash Borer Invades West Rock
The emerald ash borer, an insect native to Asia, is killing the ash trees at West Rock Ridge State Park and there is no practical solution at the moment to save them in the forest.
I have seen the dead ash trees across different parts of West Rock, along the Sanford Feeder, which is Regional Water Authority property, and on the Darling House property in Woodbridge. I have also seen them in the Naugatuck State Forest in Oxford, Beacon Falls and Naugatuck.

The larvae kill the trees by eating phloem, cambium, and xylem inside the bark, which disrupts the flow of nutrients in the tree. A tree typically dies within two to three years of being infested. One concern is that the dead trees are prone to simply falling over, which presents a hazard to forest users. The other concern is the loss of an important forest tree.

Ash trees are estimated to comprise 5 percent of the trees in a forest. From my own informal observations, I see ash trees in scattered located at West Rock where oak, beech, birch, and maple trees are far more common. One positive sign in this infestation is that the borer feeds exclusively on ash trees, so other native trees will not be harmed.

The dead trees are mostly easily recognized by a phenomenon called “blonding” in which woodpeckers strip off the dark outer bark to reach the borer larvae, leaving the light-colored inner bark showing. Another telltale sign of borer damage is the D-shaped holes created by the adult insects where they tunnel out of the trees; the flat part of the D is on the top of the holes. If the bark is completely removed, the tunneling from the larvae is clearly visible.

The bright green colored adults are about a third to a half inch long. The adults resemble the native six-spotted tiger beetle. The state is investigating the use of a parasitic wasp from Asia to kill the eggs and larvae. For ash trees on cultivated properties, insecticides are a possibility to save trees that are not heavily infested.

The insect was first spotted in Michigan in 2002, and likely arrived on wood packaging materials from Asia. The borer has spread rapidly across the country, arriving in Prospect, Conn. in 2012. Sightings were confirmed in Hamden in 2014.

The most important advice people can follow is “don’t move firewood,” as moving infested ash trees is one reason why the borer is spreading so rapidly. The state has strict regulations regarding the movement of firewood, as a result of the borer infestation.

Some of the information from this article came from the following websites, which have more details than this quick article can provide:

Connecticut Agricultural Experiment Station:, Connecticut Department of Energy and Environmental Protection:, Midwest-based Emerald Ash Borer Information Network:

This ash tree along the Regicides Trail in January 2017 shows extensive "blonding" caused by woodpeckers stripping away the darker outer bark to get at the emerald ash borers that killed the tree.
A closer look of the "blonding" caused by woodpeckers stripping away the darker outer bark of an ash tree. Small "D" holes are visible in the bark.
An even closer look of the "blonding" caused by woodpeckers stripping away the darker outer bark of an ash tree. Small "D" holes are visible in the bark. The adult emerald ash borers create these holes when they tunnel out of the tree.

Animal Invasive: Gypsy Moth Caterpillars
The gypsy moth caterpillar is present at West Rock, but not in large numbers. West Rock was spared the destruction that central and eastern Connecticut endured in 2016 and 2017 when gypsy moth caterpillars denuded oak trees, their favorite food. They had a definite impact on the woods in adjacent Woodbridge, as seen in the photo below.
Their egg sacs are a tan oval about the size of a quarter that can be seen on trees. Experts say that simply scraping them off the tree is not enough; the eggs need to be soaked in oil, or covered in soapy water to kill them. The caterpillars are distinctive with their gray-black bodies with blue and red dots.
In 2015, I found many dead caterpillars along the Yellow Trail, apparently killed by the fungus that is fatal to them. In 2016, there was so little rain, the fungus was not activated. There was plenty of rain in Connecticut in 2017, but the caterpillars ate through many trees before it activated.
Information from the state of Connecticut on gypsy moths:

The thin canopies of trees attacked by gypsy moth caterpillars can be seen in Woodbridge in this view from the Regicides Trail, June 2017.

A gypsy moth caterpillar crawls along a fern on the Darling House Trails in Woodbridge, June 2017.

Undesirable Native Insect: Eastern Tent Caterpillar
The eastern tent caterpillar is sometimes mistaken for gypsy moths, but their tents, usually found in the forks of cherry trees are unmistakable. While native, they cause problems for cherry and other fruit trees by munching on their leaves. Breaking open the tents with a stick allows birds to eat them. Links:

The white protective tent created by eastern tent caterpillars is very visible along the Regicides Trail, May 2017.

Animal Invasive: The Graffiti Artist and Litterbug
This is a two-legged invasive that somehow think is it okay to spray paint words and drawings on the park’s rock surfaces and the pavement at Baldwin Drive. I have yet to catch anyone and don’t know how to control them, but they certainly detract from the park’s beauty.

The litterbug variation leaves behind bottles, cans, cigarette wrappers and other trash. They somehow think that tossing the trash into the weeds, where it is harder to retrieve, is somehow better than just leaving it along the parking lot.

There are most likely other invasives at West Rock that I have not yet learned to recognize, but these are the ones to be found there.

Painted-over graffiti on the pavilion at the South Overlook,
as seen from the Regicides Trail.
Invasive-Free Areas
I would like to end this on a positive note by mentioning that there are many invasive-free or limited-invasive areas at West Rock, particularly the White Trail between Lake Wintergreen and its northern terminus at the Red Trail near Mountain Road. The Orange, Purple and Yellow Trails seem relatively uncontaminated, as are northern portions of the Blue Trail.

Invasive Plants Web Links

  • The Plant Conservation Alliance's Alien Plant Working Group website is an excellent place to start learning about invasive plants. The alliance is a group of ten federal agencies working with about 290 other conservation groups on this issue. The website is subtitled Least Wanted: Alien Plant Invaders of Natural Areas identifies the problem plants through words and photos, and includes treatment options. The plant list is available in several forms, including a list by common name and scientific name,, and by photo: Most of thhe direct links on this page for each invasive are taken from this website.
  • The Invasive Plant Atlas of New England provide a variety of information, including a clickable list of plants and in which counties they are found, and also a list of plants with information and photos about them. You see the photos after you click on the link, so you need to know the common or scientific name of the plant to identify it. Main page: and lists by species:
  • If you have some time to search, the University of Wisconsin-Madison has an interactive Weed Identification and Management Guide. The website guides users through a series of steps and questions to identify a weed unknown to the person:
  • The New York Invasive Species Clearinghouse has excellent resources about all types of invasive species, both animal and plant, and aquatic and terrestrial at
This poster was developed by the New York Invasive Species Clearinghouse. If you would like a copy mailed to you, contact the clearhouse at
The direct link from which I downloaded this image was


  1. Do coyotes count?