Watercress AKA Nasturtium officinale  

When I first saw this plant growing along the edges of Merrick Brook years ago. I thought "Oh wow, it's watercress!"  Now that I have been researching invasive plants for a while, I have to admit I was pretty disappointed to find this plant on the list of outlaws. It's Latin name Nasturtium officinale makes you wonder what they were thinking when they named it. Its flowers and foliage don't resemble those of a Nasturtium in the least.  They are distant cousins though, and both plants have that pleasant peppery taste when nibbled.  You often find the word officinale incorporated into part of a Latin name for a plant. It simply means it is a plant used in medicine herbalism or cookery.  Watercress, which is native to Eurasia, is one of the oldest known leafy vegetables to have been consumed by humans.  Now found in many locations across the globe, it was introduced to America in the 18th century.  

The plant is in the mustard family, and like others in that family, it is considered a cruciferous vegetable because the four petals of the flowers, which form in clusters, resemble a cross or crucifix.  If you look closely at the flowers of Garlic Mustard, as well as kale, turnips, broccoli, and radishes you will see the same flower formation.  All of these are considered cruciferous vegetables, and being so, they are quite healthy veggies to consume. I am going to insert a consumption warning here.  

If you are planning to eat watercress found in the wild, first of all, as with any plant you might be foraging, be certain you have the proper identification.  Also, in the case of watercress, be certain you are harvesting from an extremely clean water source.  Otherwise, the plant could contain giardia, a parasite that beavers are notorious for carrying.  Perhaps even worse, if the water has been contaminated by manure, you may ingest a parasite called liver fluke, and that doesn't sound at all pleasant!  

The peppery flavor of the plant is actually part of the plant's defense system.  It is caused by two compounds contained within the plant that combine whenever the plant is injured.  For all its attempts at self-defense though, that zippy flavor does not stop ducks, muskrats or deer from eating the leaves.  Those particular herbivores seem to have gourmet taste, and they are one of the contributing factors to the plant's redistribution and spread along our waterways. Watercress is also a prolific producer of seed, which is another means of its spread. Portions of the plant can also be dislodged and carried downstream during heavy water flow where they can take root and form new colonies.  

I have never seen an exceptionally large colony of this plant in Merrick brook, or in the Shetucket River, but this plant does have the capacity of creating a rapid growing blanket of greenery that floats on top of the water, crowding out native vegetation and many of the things that rely on native vegetation to survive.  A large enough mat can deplete the water of oxygen. If you have a large infestation of this plant, you should make an attempt at its control.  

HOW TO REMOVE

This plant can be hand pulled very carefully so as to capture the entire root system and prevent regrowth.  After being pulled it should be bagged and removed from the site.  It is fine to just deposit it in the trash.  

When writing about various invasive plants and including a "how to remove" section I decided to include all of the recommended options provided by reputable sources, so please don't shoot the messenger! I am not a big fan of using herbicides and putting them in direct contact with a body of water seems almost unconscionable, but there are instances when their use is the lesser of two evils, and there are herbicide mixtures designed specifically for aquatic use. If you are dealing with a particularly large infestation of watercress that is crowding out other plants and depleting the water of oxygen, you may want to try one of the aquatic herbicides

     Autumn Olive AKA Elaeagnus umbellate & Russian Olive      Elaeagnus augustifolia 

Autumn olive and Russian olive are both hardy branching shrubs that grow in a form that resembles bush honeysuckle.  All of these shrubs produce a profusion of berries. Bush honeysuckle, autumn and Russian olive are all considered invasive, but should you wish to identify them, an easy way to tell the "olive" shrubs apart from bush honeysuckle is to examine a branch.  The bush honeysuckle has leaves that grow in opposite fashion, directly across from each other along the stem.  Both the Russian Olive, native to Eastern Europe and Central Asia, and Autumn Olive, native to China, Japan and Korea, have leaves that grow in alternate fashion along their stems.  If you snip a stem or branch from any honeysuckle, you will find a tiny hole in the center of the branch.  The branch of a honeysuckle shrub has a very narrow hollow portion in the center.  

Russian Olive was introduced in the early 1900's and Autumn Olive a bit earlier around 1830. Both were imported for their value as a wildlife habitat, as well as for erosion control, and their ornamental appeal.  The two "olives", which are technically not olives at all, readily escaped cultivation.  At this point they have both been declared an invasive species over most of North America and Europe. Positive identification of which "olive" species you are dealing with does not really matter because elimination strategies for either plant are similar.  In fact, the plants themselves have more similarities than differences.  For the sake of accuracy though, you can tell the two apart most easily when the shrub is in either its flowering or fruiting stage.  Autumn Olive has white or creamy yellow flowers.  When the fruit is mature it is red with silvery speckles or scales on its skin.  The Russian Olive has brighter yellow flowers and a fruit that is more yellow orange with silver speckles when mature.  Other more subtle differences are in the shape of the leaves, with the leaves of Russian Olive narrower in form than those of the Autumn Olive.  Russian Olive foliage appears more silvery due to the fine fuzz like hairs on both the top and bottom sides of the leaves whereas Autumn Olive has fuzz primarily on the underside of the leaves.  Both of the shrubs have thorns but they are fewer in number on Autumn olives.  Both bear abundant fruit which is edible and nutritious for birds, wild animals and, when the fruit is fully ripened, people as well.  The fruit of either variety is usually fully ripened by October.  Autumn Olive fruit will be bright red with silvery specks.  It usually gets sweeter after a frost and it remains on the shrub through November.  The fruit of Russian olive may not have as desirable a flavor or texture.  If you intend to eat this fruit please be certain you have made a positive identification.  Do not confuse the plant with bush honeysuckle as that fruit considered toxic for human consumption.  If these plants provide such an abundant food source, why should we attempt to eliminate them?  The thing is with their rapid growth and prolific seed production they out-compete many native plants.  They also have the ability to increase the nitrogen level in the soil in their vicinity.  The increased nitrogen level benefits autumn or Russian olive, but other plants that are native to our region may not find all that nitrogen beneficial.  

HOW TO REMOVE

If you happen to have them, goats really like to forage this plant.  They also love Multiflora Rose, and a variety of other invasive species.  If you allow goats to consume Autumn or Russian Olive plants while adding other non-invasive forage options, eventually the alternative forage options will crowd out the Autumn or Russian Olive eliminating those invasive plants.  If you are not fortunate enough to own goats, hand pulling of small plants is recommended.  This is best done after a good soaking rain which softens the soil allowing the roots to be pulled more easily.  Try to remove the entire root system as this plant may regrow from fragments left behind.   Repeated cutting of shrubs will eventually deplete the root system, but you need to be vigilant, continually cutting back regrowth.

During their active growing season, especially during the later part of their growing season when the crown of the plant is passing nutrients back down to the roots, the shrub should be cut as low to the ground as possible.  Follow up with an herbicide application to the cut stump to prevent regrowth.  Triclopyr is the preferred herbicide to use to eliminate this plant.  It should be used in its undiluted form for the cut stump treatment.  Another method for herbicide application is to prune the shrub back to a lower level and use triclopyr as a foliar spray when the plant resprouts and has fully formed leaves.  The leaves are what take in the poison.  Cutting the plant back first allows for the use of less herbicide during foliar application and it also makes it easier to reach all parts of the plant with the spray.  Be sure to follow the dilution instructions and all other instructions on the product's container.  Always wear protective clothing, and spray herbicide on a calm day.  

 Invasive Plant Walk Talk & Cut at the Scotland Public Library

On August 30, 2025, our group of twelve or so joined up with Rose Hiskes and Dr. Charlotte Pyle of The Connecticut Invasive Plant Working Group to learn more about invasive plants and native plants as well.  The day was clear and absolutely perfect. As we hiked along the trail, I came to realize how enjoyable it was to meet with like-minded people all of whom were well informed about the impact invasive plants are having on our landscape.  Rose and Charlotte were especially knowledgeable, providing us with botanical terminology and various ways to detect some of the invasive species no matter the season.  In addition to the invasive plants, they pointed out some exceptional native specimens growing along the trail.  

The trail along the boardwalk at the library is a soothing and peaceful spot.  The boardwalk itself is truly special, definitely worthy of preservation, as the boards used in its construction were purchased years ago by town residents and inscribed with their names or names of their loved ones, past and present residents of our town.  Unfortunately, over the years, the entrance to the boardwalk became so overgrown that you might not even realize the trail existed. 

After our informative walk with Rose and Charlotte, and a wonderful lunch which included a variety of delicious pizzas, a generous donation from our town's nip fund, we returned to the trail armed with energy, clippers, and various brush cutting tools.  About two hours later our group amassed a huge pile of invasive bittersweet, multiflora rose, and burning bush branches. I am excited to report that the opening to the trail is now once again visible!

After posting various "Wanted Reward for Outlaw Plant Posters" for invasive plants linking to articles this website, I was asked "What exactly is the reward?"  I can now affirm there are numerous rewards.  The camaraderie of working together with people is probably the most important one.  There is also the reward of accomplishment you feel when you step back and see the impact your work has made.  Then there is the reward of acquired knowledge.  In addition, a little bit of exercise can also be kind of rewarding.  Depending on which side of 60 you fall on, you might feel a tad achy the following morning from stretching to cut vines and from pulling out roots, but even that actually feels pretty good.

We will be meeting again in the not-too-distant future.  Feel free to join us next time if you missed the opportunity the first time.  I will keep you posted as to the date on the Scotland Residents FB page.  At the next meeting there will be no limit to the number of participants.  Stay as long as you can.  You don't need arrive at the beginning or to stay to the end of the work period.  Any help you can offer will be greatly appreciated.  Let's work together and get this trail back into shape!

Come Join Horticulturists Rose Hiskes and Dr. Charlotte Pyle at the Scotland Library!  Take A Walk and Learn More About Invasive Plants.  The program is free of charge, and lunch will be provided. 

On August 30th, 2025 from 10 AM to 1 PM rain or shine you are welcome to join The Scotland Invasive Plant Working Group, and our guests Rose Hiskes and Dr. Charlotte Pyle at the Scotland Library to learn about invasive plants. This program is limited to 12 participants.  Registration needs to be made by August 8th.  If you would like to attend, contact Rose.Hiskes@ct.gov to register.

Take a walk with us along the boardwalk trail through the woods at the Scotland Library.  We will be accompanied by horticulturists Rose Hiskes of the Connecticut Invasive Plant Working group and the Connecticut Agricultural Experiment Station and Dr. Charlotte Pyle a forest and landscape ecologist, and co-chair of the Connecticut Invasive Plant Working Group.  

The first part of the event will be an interesting learning opportunity with Rose pointing out both native and invasive plants along the way.  She will explain various methods of identification methods observing foliage, bark, flowers, and various other growing characteristics. She will make recommendations on how the invasives can best be eliminated or at least controlled.  Dr. Pyle will suggest alternative native plantings that we could add that would be adaptable to the environment along the trail once the invasives are removed.  

Our town is providing lunch at no cost to attendees.  After lunch, we hope to begin removal of some of the invasive plants.  If you have never walked here, I would describe it as a beautiful little trail, actually an elevated boardwalk, that begins in front of the Scotland Public Library and connects via town land to the fire station.  The trail is definitely worthy of some cleanup and landscaping. Attendees should wear appropriate footwear, as we will be working in the wooded areas alongside the boardwalk.  Prepare for ticks by tucking pants into socks.  Bring a pruner and gloves.  This is a rain or shine event, so hopefully the weather will cooperate!   

 

                                                            Callery Pear in Bloom

                                     Sharp thorn-like growths

                                           The Round Fruit

Callery Pear AKA Pyrus calleryana

This spring, for the first time, I noticed a small attractive tree with showy white flowers growing near the border of a state-owned field across from our house.  It being something new to me, I snapped a picture of it and asked my smart phone for an ID.  The phone readily complied suggesting the tree was a wild Callery pear tree.  In searching for more information, I found first of all that The Id. provided by my phone was correct, and secondly that these trees are yet another invasive plant. 

Here is a tad of history about how they arrived on our shores and how they became invasive should you be interested.  The trees were brought here from China, along with many other plants, during the early 1900's.  It is during this time period that ranching in the Pacific Northwest began to transition to farming. Many trees and plants likely to survive in that climate were transported from not only various parts of the United States, but from other countries as well.  Great emphasis was placed on exploring China for potential imports as the climate in parts of China was similar to that of the Pacific Northwest. It was believed plants from those areas in China would likely survive and thrive here.  Previously, in the Pacific Northwest, orchards had been planted with numerous French pear trees. Sadly, multitudes of these trees were succumbing to a disease called fire blight.  A diseased tree would exhibit branches and leaves that appeared shriveled, looking exactly as though they had been through a fire.  Just in the nick of time plant explorers in China discovered the extremely hardy Callery pear tree.  The trees were so self-preserving they even had spiny thornlike growths along their branches which deterred wildlife from grazing on them.  Grafting the French pear trees to Callery pear rootstalk seemed like the perfect solution for the survival of the diseased French pear trees.  Callery pear seeds were imported from China by the thousands and from them thousands of trees were successfully grown, and varieties of the less hardy pear trees were then grafted to them.  Problem solved?  Well yes and no. The fire blight issue was resolved, but let's fast forward to the year 1952.  This is when John Creech from the USDA happened to observe one of the older remaining Callery pear trees that was being grown as potential rootstalk.  The glossy leaves, the globular form, and tree's showy bloom struck him as very appealing.  Additionally, this particular Callery pear tree did not exhibit the usual sharp thorn like spurs on its branches.  Seeing its potential as a landscape tree, he started several scions, essentially clones, from cuttings of the tree's branches and named the resultant trees Bradford pear trees. The USDA continued to grow more and more of these clones. During the housing boom in the 1960's, the Bradford pear trees were heavily marketed.  After the successful marketing campaign, the trees were found just about everywhere.  Bradford pear trees are not self-fertile.  Even if you plant two Bradford pear trees near each other they are essentially sterile. Therefore, Bradford pear trees could safely be grown as ornamental trees without danger of overpopulating the environment. 

By the 1980's, as the trees matured, problems with branch breakage, sometimes resulting in total tree breakage, began to occur. Since the tree was such a popular ornamental, alternative cultivars were developed, each, on its own, essentially sterile.  This is where the invasive outlaw problem began.  Unfortunately, the several different cultivars of Callery pear trees developed and marketed in the 1980's, though sterile individually, were able to cross pollinate with each other. They could also cross pollinate with the Bradford pear.  In addition, the new cultivars were capable of cross pollination with cultivated orchard varieties of fruit bearing pear trees.  The seeds and resultant trees from cross pollinated ornamental pear trees reverted to the original imported Callery pear trees with all of their wild traits, including the trait of those tough sharp 4" thorn like spines!  The wild Callery pear trees are no longer sterile.  They bear numerous small round fruit each containing several seeds within.  As some of that fruit is consumed by birds, the seeds pass through their digestive tracts and are scattered through the landscape while the birds are on their travels.  Eventually these seeds germinate creating a new colony of wild thorny pear trees also capable of reproducing.  Any fruit not consumed drops close to the original tree and germinates in place beginning the creation of a thicket of these invasive trees.  As if that is not enough, the trees send out lateral roots occasionally sending up shoots forming yet more trees. Dense thickets of these thorny trees can prevent wildlife from passing through and birds from nesting.  Woodland areas infested with these invasive trees become unpassable for human recreational activities as well.

So, how exactly did that tree get in the field across from our house?  I believe the Bosc and Bartlett pear trees growing in our orchard somehow became cross pollinated with a Callery pear tree, either a wild one or somebody's ornamental.  Several years ago, a gang of criminal squirrels harvested our entire crop of perfectly ripened pears for themselves. They are the likely culprits responsible for planting the Callery pear tree I observed in that field, and I fear there will be more!  

You can readily identify a wild Callery pear tree.  Its leaves look glossy and similar in form to that of a regular pear tree.  The wild Callery pear has the numerous sharp woody thorns that grow along its branches.  Another identifying characteristic of either wild or cultivated Callery and Bradford pear trees is the abundant showy white flowers which are said to smell like rotting fish or urine.  The odor attracts flies which are the trees primary pollinators. I have to say I did not notice that odor when I photographed the wild pear in the field for smart phone identification, but I did not get all that close to the tree either. Callery pears are considered invasive in many states including Connecticut.  According the UCONN invasive plant list, Callery pear cultivars will be banned for sale in Connecticut beginning in 2027.  Beware! as of 2025 Bradford pear and Callery pear cultivars are still being sold in Connecticut!!  There are many attractive native alternatives that bear flowers that don't smell like urine or rotting fish! Select one of those instead.

 

Second year in bloom

First year rosette

Spotted Knapweed - AKA Centaurea maculosa, Centaurea steobe

This is a plant I am a bit sorry to see on the outlaw list.  I am sure you have seen it in town and growing in patches along the highways.  The plant produces lots of pretty pink flowers in July often in areas you wouldn't believe anything could possibly grow.  It often frequents neglected areas with sandy gravelly soil, for example our town transfer station, along railroad tracks, sandy roadside ditches, vacant lots, etc.  I used to believe this plant, with its attractive summer blooms, added an aspect of hope to sites otherwise devoid of beauty. At one point I actually thought about adding it to one of my gardens.  Fortunately, I did not.  With its aggressive growth habits, I definitely would have regretted it.  One really shouldn't move plants from the wild to one's own garden until it is known exactly what you are dealing with, or for that matter if it is even legal.  

Spotted knapweed, a member of the aster family, is native to Western, Central, and Eastern Europe where it along with other plants from the Centaurea genus, has an ancient history of medicinal use.  It is considered a biannual forming a short rosette of leaves in its first year.  During its second year it grows to a height of about two feet and produces flowers.  The flowers are a good source of pollen and nectar for our native bees as well as honeybees which are native to 

Europe imported here during the 1600's.  Interestingly honeybees when first introduced were referred to as White Man's flies by Native Americans.  Spotted knapweed is among several plants employed by beekeepers to increase honey yield.  While that may prove profitable in the near term, if invasive species are allowed to take over, the lack of variety of nectar and pollen throughout the season by native plants is guaranteed to have a negative effect on native bees as well as honeybees.  Spotted knapweed is an extremely prolific seeder, with a single healthy plant producing around 1000 seeds.  With that quantity of seed production this plant has the capacity of crowding out native plants, additionally it is yet another invasive plant with allelopathic properties, producing a chemical that discourages other plants from growing near it.  Fortunately, seed production is this plants primary means of spread.  When colonies are growing on sandy riverbanks the likelihood of erosion increases because of this plant's frail root system which does not hold the soil in place very well, especially during heavy water flows.  With its heavy seeding, if in a pasture setting, spotted knapweed has the capacity of rapidly taking over grazing areas providing less diverse food for wildlife and certain livestock.  

 How To Remove

Small colonies can be easily managed by hand pulling with help of a shovel or trowel.  The use of gloves is recommended as some may have a sensitivity to this plant.

Herbicides containing 2,4-D, Triclopyr, or Dicamba are also recommended.  To be most effective and prevent seed spread they should be applied during the time when the plant is in it budding stages, before flowers open.  Monitoring of the area and repeat application will be required as past fallen seeds remain viable for a number of years.

Biological Control

Sheep, goats and cattle will readily consume spotted knapweed in all its growing stages but especially when it is in its bolting stage, the period in mid-July when it begins to form buds and flowers. The plant has a nutrition profile similar to alfalfa when it is in its rosette stage with nutrition declining slightly when the plant is bolting. Repeated grazing will significantly reduce the presence of this invasive plant allowing for more diverse pasturage. 

Over the years several different insects have been introduced as a biological control for spotted knapweed.  Some target the flower or seed heads dramatically reducing the number of seeds the plant sets.  Other insects or their larvae damage the roots. Still others weaken plant by feeding on its leaves. The following list was taken from the USDA:

The sulfur knapweed moth (Agapeta zoegana) larvae feed within the plant's roots. The knapweed peacock fly (Chaetorellia acrolophi) larvae feed on the plant's seeds. The green clearwing fly (Terellia virens) larvae feed on seeds within flowerheads of spotted knapweed. The knapweed root weevil (Cyphocleonus achates) larvae feed within spotted knapweed roots. Larinus minutus, a seedhead weevil, larvae destroy spotted knapweed seed in the seedheads. Larinus obtusus, blunt knapweed flower weevil, larvae feed on seeds within the seedheads and adults feed on leaves. Urophora affinis and Urophora quadrifasciata are seedhead gall flies that are also used as biocontrol agents for spotted knapweeds. It is perfectly legal to move a plant that is infested with any of these insects to an area of plants not yet infested.

 

                                CYPRESS SPURGE AKA Euphorbia cyparissias

During the 1860's Cypress spurge was imported from Eurasia for its decorative appeal. Likely because of its low maintenance nature, it was frequently planted in graveyards, so much so that one of its common names is graveyard weed. Cypress spurge is a groundcover with fine narrow leaves growing in alternate pairs along the stem that eventually form whorls along the upper portion.  When in bloom, the plant is loaded with an abundance of small pretty yellow flower clusters giving it a very attractive appearance. Another of the plants characteristics is the milky substance that is exuded from the stem or root when either are broken.  This toxic lactic substance can cause contact dermatitis in some people. Originally intended as an ornamental groundcover, the plant readily escaped cultivation and has now achieved its present outlaw status. The plant is considered potentially toxic to horses and cattle, though most grazing animals will instinctively avoid it.  When I started one of my gardens, shortly after moving here, I noticed this volunteer plant growing along the back edge.  I welcomed it and encouraged it to grow.  Quickly realizing that it did not need any encouragement, my intentions changed, and I began trying to eradicate it.  It has been over 20 years now and I have yet to become successful in that endeavor.  The plant has a trailing rhizome type of root system that can reach up to ten feet.  The root readily breaks off as you pull it and new plants form from lateral buds all along the remaining root segments; so, it continues to grow in the back of my garden along the tree line right next to the poison ivy adding another level to my exasperation. As you can imagine the plants abundant flowers eventually produce abundant seeds, up to three seeds to a capsule, and to make matters even worse, the mature seed pods explode propelling the seeds up to 16 feet away!  Take my advice DO NOT ENCOURAGE THIS INVASIVE VINE!  As is true of all invasive non-native plants, the aggressive growth of Cypress spurge crowds out native species.  Because of the lactic substance exuded it is not considered a grazing plant, in fact this plant not considered beneficial for any of our native wildlife.

HOW TO REMOVE

If this plant is growing in your garden, you can attempt its eradication by pulling it. You can contain the spread this way but if you don't pull out the entire root the plant will continue to exist in your garden.  Though I have not had an issue with contact dermatitis, I suggest wearing gloves to prevent possible a possible occurrence from contact with the sap.  The most effective control method is to apply an herbicide such as glyphosate.  You will likely need to repeat application during the growing season.  If Cypress spurge is growing in your lawn or in a horse or cow pasture, the recommendation is repeated mowing every 21 days after the first bloom.  It is important to continue the 21 day mowing process as mowing encourages new growth.  If the plant is already in seed mow around it so as not to encourage further spread of the seed.  Eventually consistent mowing during the plant's growing season should deplete the plant of its growth energy.  Another herbicide you might consider is 2,4-D amine.  The first application should be at early bud stage.  A second application will be needed during the plant's growing season.  This can be a difficult plant to eradicate in a livestock pasture setting.

Biologic control

There are at least two insects that will help to limit growth of the plant.  The brown dot leafy spurge beetle Aphthona cyparissiae, and the black leafy spurge flea beetle Aphthona lacertosa.  These insects lay their eggs at the root base of the plants.  The larvae feed on the roots and the adult beetles feed on the foliage.  Actually, there have been 11 species of European insects released in North America to help control this plant.  It seems none have found the Cypress spurge in the back of my garden, at least not yet!