Invasive Plants Along Our Roadways

 

There are many reasons to be concerned about invasive plants.   I addressed their negative impact on our environment in previous posts.  Recently, after attending a meeting including our first selectman and our public works crew, I thought it a good idea to introduce a different perspective, that of our town’s public works team.  To them, maintaining a clear line of sight along our roadways for our safety is imperative.  Mowing has long been a routine part of that work, but over the years this practice has allowed leafy intruders to furtively establish themselves across the landscape. A closer look at the plants growing along our roads reveals that many are now invasive species. Although mowing helps keep them short and may make them appear under control, these invaders continue to spread from roadsides into open spaces and even onto private property. The good news is that our town is getting ready to take steps to address the problem.  Our public works department is going to be licensed to use herbicides on town property to help combat these invasive plants.

We anticipate there may be some opposition to the use of herbicide in town and hope to set your mind at ease.  The plan is to use herbicides triclopyr and glyphosate in the most conservative ways possible while still achieving the desired results.  Their cautious use will be combined with cutting and mowing and in some instances a little hand pulling.  

As you know our public works dept. consists of just two men.  Not only would hand pulling be difficult, and immensely time consuming, but also ineffective since many plants grow back if only a small piece of the root system is left in the ground.  Herbicides provide a very effective alternative.  One method that will be used is called the cut stump method.  Shrubs and vines are cut back as much as possible, and herbicide is then painted on the cut stumps. This little bit of herbicide travels to the roots preventing the shrub from growing back.  There is no overspray and provided proper safety equipment is used by the applicant there is no danger to anyone.  Targeted painting of the cut stump won’t even harm adjacent plants.  

While this method works on many plants, Japanese knotweed will require a different approach.  The present recommended approach to the eventual elimination of this persistent invasive plant is a 2% solution of glyphosate mixed with surfactant sprayed on the foliage after the blooms have faded.  This treatment will need to be repeated for several years to be totally effective.  It is worth the effort since roots of this plant have the capacity of breaking through a cement foundation.  Because it is so difficult to manage, the presence of this plant can decrease property values.  

We are beginning to see several new Japanese knotweed colonies forming throughout our town.  If you happen to spot one contact public works or your first selectman.  We would like to address the problem early before newer colonies of this plant spread out of control.   In instances where invasive plants are growing on town and adjacent private land the public works dept. will need to coordinate with the property owner to work together to eliminate the plants.  The public works department can only work on town land.  Private land is solely the responsibility of the landowner.  With your cooperation we can eliminate colonies of invasive plants and restore our native species.

 A USEFUL LINK FROM CIPWG THE CT INVASIVE PLANTS WORKING GROUP

When fighting invasive species, this is the time of year when you want to throw up your hands and give up!  The roadsides are so full of invasive plants.  They are choking off the landscape just about everywhere you look.  You might feel helpless and incapable of the task at hand.  I offer fresh hope!  This morning I came across a post with this link containing various instructions on how best to eliminate the top 10 invasive plants from CIPWIG Invasive Plant Management Calendar . It made me remember that mid to late summer is the appropriate time to get out there and fight especially if you are willing to use herbicides either as a foliar spray, cut and paint or inject.  The best time to use herbicides is when a plant is actively growing and returning nutrients to its roots.  

More on Japanese Knotweed Control

 

Credit for the above to Gregory Rosner of the Worldwide Japanese Knotweed Support Group on Facebook

MORE ON JAPANESE KNOTWEED ELIMINATION

For anyone interested in eliminating colonies of this plant using herbicide.  This method called " The Window" is considered to be the most effective.  It may take a few years to totally eliminate the colony, so patience and persistence are required. The image below was copied from The Worldwide Japanese Knotweed Support Group.

 

Japanese Knotweed Just Emerging

I recently came across a post on a Facebook group regarding invasive plants.  A person who has been attempting to eliminate Japanese knotweed from their landscape is apparently having some luck using an herbicide treatment and the method suggested by another Facebook group called The Japanese Knotweed Support Group, a group designed for people dealing with this terribly invasive plant.  My membership to this group is still pending at this time.  Should you wish to join, here is a link to that group Worldwide Japanese Knotweed Support Group |.  

Below is a copy of the Facebook post I came across recently.  It includes a method recommended by the support group. The person who posted tried the recommended method with some pretty good success. 

"I have some new sprouts coming up this year as it is a multi-year process but after spraying once last year in late September I can tell you the difference is ASTOUNDING. I really just followed the recommendation of the worldwide Japanese knotweed support group. I ordered glystar 41% concentration glyphosate which already has surfactant in it. I used a battery-operated backpack sprayer and calculated how much water to add to it to make the glyphosate a 2% concentration, and I added a couple capfuls of blue lawn dye (got everything on Amazon). I suited up with proper PPE including a mask and eye protection and used a ladder to spray the really tall stands. I tried to hit as many knotweed leaves as I could physically get to. "

This is a copy of my earlier post on Japanese knotweed 

Monday, May 5, 2025

JAPANESE KNOTWEED AKA  Reynoutria Japonica, Fallopia Japonica

Almost every time I search for or take a photograph of the "invasive plant of the week" I am surprised by the plant's decorative potential!  The first photo is a good depiction of what the plant looks like at its present stage of its growth.  The second photo shows the mature plant in flower.  Although commonly called Japanese knotweed this plant is native to all of Eastern Asia. When in bloom the plant is positively loaded with gorgeous foamy white flower spikes that are attractive to pollinators.  An interesting note is that the young shoots and leaves of this plant are edible.  The shoots have a tart flavor similar to rhubarb and can be used as its substitution in recipes.  Should you be interested, recipes for knotweed, including knotweed wine, sorbet, and chutney can be found on the internet.  If you are choosing to harvest this plant for consumption, be certain you are harvesting the correct plant and that it is not from an area that has been treated with chemicals!

How did this plant arrive on our shores?  Female plants, thought to be sterile, were first introduced in the prestigious Kew Botanical Gardens in England in 1850. During the 1880's it became a desirable exotic plant for inclusion on the property of several expansive Long Island, NY estates.  It appeared as an ornamental plant in nursery catalogs until the latter 1930's.  Even then it was under watchful surveillance as a suspected outlaw and garden escapee.  

How did this plant arrive in Scotland, CT?  One of its adapted uses was for erosion control.  Stands of it were installed on highways and state roads.  This is likely the cause of its present bounty along some of our roadsides in town.  When traveling through Scotland on our town and state roads, you can't help but notice vast colonies of knotweed so dense that nothing else grows among it.  The reason for that is that it, like some other invasive plants, it has an allelopathic superpower.  The plant's roots and other decaying plant parts exude chemical compounds that prevent other plants from growing in its midst.  The plant also has dense lush upper leaf growth, keeping any brave potential competitors from finding the sunlight they require to grow.  This is how Japanese knotweed quickly creates a monoculture.  It crowds out native species that many of our native insects and animals require to thrive. You may wonder, how did only female plants reproduce so prolifically?  There are a couple of answers to that question.  One is that are other several species of knotweed and if one of these happens to be located nearby, there is a potential for cross pollination, which would create viable seed.  This plant, however, spreads primarily through its root system, technically called a rhizome system.  Rhizomes are roots that grow horizontally periodically sending up new growth. In the case of knotweed, these rhizomes are hardy enough to penetrate through any small cracks in a house foundation or any pavement potentially causing severe damage.  In some areas, the presence of this invasive plant is actually having a detrimental effect on real estate values.  Although the plant goes dormant in the winter months and temporarily dies back when there is a spring freeze, the rhizomes remain viable underground.  Even if plant growth is suppressed and no additional nutrients are added, it is said that the rhizomes are capable of remaining viable for up to 20 years!  Any small bits of this powerful rhizome system accidentally transported by a snowplow, brush cutter or unintentionally by a garden shovel will readily form a new ever-increasing colony.  If this plant colonizes along our waterways, the diverted water flow caused by dense stands of Japanese knotweed can cause flooding and potential bank erosion.  As riverbanks erode, segments of the plant's rhizomes could be transported downstream.  Rivers brooks and streams are a virtual highway for the plant to follow. Elimination of this plant should definitely be a priority!

HOW TO REMOVE

Take a deep breath!  This is going to be a difficult but not impossible task.  It is one that will likely involve a combination of techniques possibly including the use of herbicides.

If you want to try a method that does not use herbicides the present recommended method is to cut the plant back three times during its growing period.  Once in June, again in July, and last in late August.  The repeated cuttings are meant to keep the plant from flowering.  Cut as low to the ground as possible.  The stem has what look like joints or notches which are called nodes.  You want to cut the plant beneath the plant's lowest node.  Cutting the plant numerous times also helps to reduce the plants energy transfer to its rhizomes.  After cutting, the knotweed patch can be covered with black plastic carefully weighted around the edges.  The cut stems should be placed in contractor bags and disposed of in regular trash.  Do not compost them, as any pieces of attached rhizome could sprout in your compost pile! This method of removal will need to be repeated for at least three years.  Continue to monitor the area as this plant can be very persistent. 

If you are comfortable using herbicides, The recommended method is to cut the plant back to 2 to 3" in late May or June, and then let it grow until August.  Spray before the plant flowers using glyphosate with an added surfactant or with triclopyr.  Many pollinators feed on this plant so spraying either before flowers form or after the flowering stage is complete is essential so as not to harm them. Cutting the plant back in the spring reduces the height of the plant, therefore the amount of chemical needed for coverage.  The same protocol will need to be repeated the following year.  After the second year of treatment, plant the area with some native species such as Joe Pye weed to reduce the growth of Knotweed.  You will likely need to continue treatment every two years following the second treatment.

Biological Control:  An insect called Japanese Knotweed Psyllid or Aphalora itadori was introduced in 2020 as a possible biological control method.  The insect is host specific to Invasive knotweed.  During all of its life stages, the insect consumes the sap from the leaves and stem.  This in theory weakens the plant.  In the United States in 2020, several releases were done in areas including Rhode Island and Massachusetts.  Other releases in the UK and Canada done back in 2010 have resulted in populations of the Knotweed Psyllid having established a presence in that area. It remains to be determined how successful the release of this insect in the United States will be.

Bulblets

 Dicentra cuclaria AKA Dutchman's breeches, Little blue staggers

You can't help but laugh when you see all the cute white pantaloons hanging off this plant!  It is a plant native to Connecticut and New England, a perennial with an early spring bloom.  Both the flowers and the finely compound lacy fernlike leaves are attractive.  It is a perfect native plant for a shaded or semi-shaded spot with rich organic soil. Keep in mind that the leaves and flowers will die back completely after the bloom period so the plant will virtually disappear as the season progresses.  The bulblets in the ground will remain viable and the plant will reappear the following spring. Although the flowers do not have a fragrance, they are attractive to bumblebees.  The flowers are designed so that the bumbles separate the petals with their front legs and gather pollen from the anthers with their center legs. Pollinated flowers eventually produce a long pointed seedpod. The seeds within have sweet eliasome coating prized by ants who bring the seeds to their colony where the coating is consumed.  Ants being the good housekeepers that they are, will discard the seeds to their nutrient rich refuse pile after the coating is consumed.  There the seeds will eventually germinate.  This process, called myrmecochory, is shared by numerous plants.

I do not recommend using this plant for any purpose medicinally as it contains dangerous compounds.  However, Dicentra cuclaria does have a history of medicinal use by Native Americans and early European settlers including use as a cure for Syphilis.  The plant which is now considered to be in the papaveracae family contains isoquinoline alkaloid compounds.  These alkaloid compounds are the source of the plant's other common name Little blue staggers.  This is not a safe plant for livestock to graze on as the compounds contained can cause drunken staggering and even death, hence its other common name.  This is not a safe plant for humans or other animals to consume any part of!

 

Viola sororia AKA Common Blue Violet 

I love when in early spring our back yard becomes blanketed with violets!  These beautiful wildflowers are called Viola sororia.  They are a plant native to Connecticut, one that is not only beautiful but edible. There is a close imported look-a-like called Viola odorata, a variety from Europe.  Viola odorata shares many aspects of our native violet but its flowers have a pronounced sweet fragrance.  Viola odorata flowers are considered just as edible as our native violets. Most species of viola are edible including Johnny jump ups and other pansies. Historically our native Viola sororia was a source of both food and medicine for Native Americans. The flowers which range in color from white to various shades of purple can be eaten freshly picked.  Simply toss raw flowers into salads where they will add a colorful accent. Fresh flowers can be frozen into ice cubes or pressed into a soft cheese such as brie.  The flowers can also be preserved for a time as crystalized violets.  Crystalized violet flowers are a delicate confection impressive when used as a decoration on a cake or a garnish floated atop a drink. To make them, simply dip the flowers in slightly beaten egg whites, then dip in granulated sugar. Place the flowers on a parchment lined cookie sheet in a slightly warm oven until they are dry to the touch.  Stored in airtight containers in a dark place, they will keep for several months before the color fades. Just today I found out that the heart shaped leaves of this plant are edible as well!  The leaves can be steamed like spinach.  Although I have yet to try the steamed leaves, the flavor profile is said to be similar to peas, so I imagine slightly sweet. It is advisable to wait until the plant is in bloom before gathering violet leaves for consumption so that you are certain that you have accurately identified the plant.  Please be certain any plants you gather have not been treated with chemicals!

Here is an interesting fact regarding pollination and reproduction of this plant.  The plant forms two types of flowers, the above ground flowers that we are all familiar with.  These are the flowers visited by the pollinators of which there is a diverse group including honeybees, bumblebees, and various beetles, flies and moths.  However, to assure its continued existence perhaps in the case of an especially cold year with lack of insect pollinators, the plant also produces a group of self-pollinating flowers that lie beneath the soil.  These flowers never actually open but do produce seed. If you have ever pulled out a clump of invading violets from your garden, you may have observed some of these closed flowers growing among the rhizomatous root system.  The technical term for the underground flowers is cleistogamous flowers versus the above ground flowers which are chasmogamous flowers. 

 

Erythronium americanium AKA Trout Lily, Yellow Dog Tooth Violet  

This a beautiful little flowering plant is native to Connecticut, and a harbinger of spring.  The leaves have a mottled splotched pattern as well as a shape that much resembles the body of a trout hence Erythronium americanium's most common name trout lily.  You will find this plant growing on the damp forest floor during the months of April through May where it takes advantage of the sunlight before the forest canopy fills in.  The plant is a reluctant bloomer with only a fraction of plants producing blooms during the month of April.   A short time after any blooms fade the foliage of all the trout lily plants dies back for the year.  The leaves turn yellow and wither away returning again the following April. 

 Many of the trout lily colonies you encounter in the woods can be hundreds of years old.  When you encounter a large colony, you will likely notice only one or two plants with flowers.  Because the flowers are one of the first in the season to bloom, they are pollinated almost without fail by bees that are extremely hungry after a long winter.  A great deal of energy goes into producing any of the flowers you see. It may take up to five years of stored energy to produce a flower.  The stored energy comes from the process of photosynthesis, which these days may be best explained using the analogy of a solar panel connected to a battery. A solar panel gathers energy, and when connected to a battery any of that energy not expended for other things is stored within the battery for future use.  In the case of the trout lily, it can take up to five years of stored energy finally allowing for the production of a single bloom making you wonder how a colony of trout lilies can be so massive when there are so few flowers resultant in so few seeds.  Trout lily plants have a second method of reproduction, an unusual cloning method.  Each plant sends out a long slender threadlike stem called a dropper.  These droppers grow up to 10" long.  As they grow, they turn a 45-degree angle and burrow deeply into the ground.  After planting themselves the droppers gradually form a corm (sort of a bulblike structure) that grows into another plant.  This is how trout lilies are able form a dense carpet on the forest floor.  The seeds that form from the flowers are also viable.  Several are produced within a capsule.   They are designed to be planted by ants.  Each of the seeds within the capsule is coated with a sugary substance irresistible to an ant.  They carry the sugar-coated seed home to share with their buddies. After the coating is consumed, the seed gets tossed in their trash pile where it eventually germinates creating another trout lily plant that over time given the right growing conditions can develop into a new colony. The ant feeding process is called myrmecochory.  A variety of plants share this method of survival.