Incised fumewort (Corydalis incisa). Photo: Miri Talabac, University of Maryland Extension
Have you seen incised fumewort (Corydalis incisa)? This frilly, little wildflower is surprisingly invasive. Originally from East Asia, this species has been spreading southward along the I-95 corridor from New York since 2005. The first iNaturalist observations of incised fumewort in Maryland were made in the spring of 2018. As of this writing, Maryland contains 259 Research Grade observations. Many gardeners report that the seeds must have been present in potted plants or mulch that they purchased. In our parks, incised fumewort quickly outcompetes native spring wildflowers, and particularly dramatic declines in Virginia bluebells have been observed in the Bull Run floodplain (Northern Virginia).
Incised fumewort came into bloom in mid-March this year and normally continues blooming until early April. Seeds ripen within three weeks of blooming. Ripe seeds are explosively dispersed up to 10 feet away from their parent plants. They may also be dispersed by flowing water, tracked mud. Some reports indicate they are dispersed by ants.
Gardeners and landscape maintenance professionals tell us that manual control is unreliable at best. In some cases, even very persistent, frequent episodes of manual control have failed. Chemical control is more effective, but has its own challenges, such as unintended damage to nearby native plants.
In either case, it helps to understand that the species is biennial. The flowers of second-year plants are easy to see, but seedlings are inconspicuous. If management only targets flowering plants, that can be a viable strategy. But for folks who didn’t realize there were also seedlings present, it can be shocking to see that despite all your hard work there are even more flowering plants the next year. This gives the impression that management is failing, which may or may not be true. My casual observation is that seedlings (dicotyledons present) germinate in both spring and fall. I suppose the spring germinators go dormant for the summer and re-emerge in fall while the other seeds are germinating. The resulting rosettes are fully evergreen. The rosettes have a small, soil-colored tuber. For those of you doing manual control, make sure to remove it.
You can help by reporting this plant when you see it. You can do that quickly and easily using the iNaturalist app. Just point, click, and upload. There is even a space there where you can leave us some notes. Your observation will contribute to a publicly available map that is used by many land management agencies and their volunteers (Weed Warriors) to prevent new infestations from becoming established.
By Sara Tangren, Ph.D., Environmental Program Coordinator, National Capital PRISM, Metropolitan Washington Council of Governments. This article was published originally in the University of Maryland Extension IPM Alert, March 22, 2024.
Invasive Asian honeysuckle (Lonicera sp.). Photo: Rachel J. Rhodes, UME
Eliminating unwanted plants is often one of the most challenging chores that gardeners face. Not introducing invasive plants is the fastest and most economical way to make a positive impact, as once invasive plants are introduced to your garden, it can take many years to eliminate these invaders from your landscape.
Invasive plants propagate and spread by many different methods, which makes controlling them difficult and different for each species. Please learn feasible control tactics provided by land-grant universities or Extension factsheets/webpages before starting. Fact-based research is the absolute first step in getting ahead of plant invaders. Often invasive plants cannot be controlled 100% in just one growing season, but preventing the plant from making seeds or spreading is better than doing nothing at all.
Questions to guide your research:
Get proper plant identification! Use Ask Extension, Local Extension Professionals, and Master Gardener Plant Clinics. Smartphone plant ID apps can give you some idea, but you should follow up and confirm the correct identification. Apps may be limited by photo quality and geographic area.
Is the plant a woody perennial, herbaceous perennial, or annual?
Has the plant been a problem for several years in your landscape, or is it a relatively new concern?
You must know how it is reproducing/spreading in your particular situation. For example, if the plant reproduces from stem/root cuttings, the last action you want to take is to mow/weed-eat/till the roots, which would cause the plant to produce hundreds of new plants.
If controlling 100% is not a feasible option, determine how you can prevent the plants from spreading or allowing them to get stronger.
If you have an invasive plant in your landscape and you really enjoy it, learn how to prevent it from spreading. For example, the spread of some plants can be prevented by removing flowers/viable seeds so that wildlife does not consume and spread them, or so that wind/rain does not blow away the seeds.
Always include “MD Extension” with internet search engines to be sure that identification and control tactics specific to Maryland are being filtered to the top of your results.
Three basic control options are categorized below.
Mechanical control
Mechanical control options are often the first step that people take in controlling unwanted plants; however, these are by far the most physically demanding and often lead to a high level of site disturbance. Examples of mechanical control are:
Pulling and digging.
Suffocation or smothering with landscape fabric, mulch, cardboard, multiple layers of newspaper, anything to block the sunlight and prevent the plant from growing.
Solarization: laying plastic over the plants to “cook” live plants and viable seeds with the heat that builds up underneath.
Cutting, repeated cutting, or mowing in hopes of weakening stored nutrients so that the plants can not regenerate. This is also done to remove the flowering/seed structures.
Biological control
Biological control options utilize something else that is alive—insects, fungi, grazing livestock animals, etc. More and more of these options are being explored; however, sometimes the control agent may be 100% specific to the problem plant, or sometimes it may be able to feed on other plants too, which is the case with the Kudzu bug.
Kudzu bug (Megacopta cribraria). Photo: Russ Ottens, University of Georgia, Bugwood.org
Chemical control through herbicide application
Foliar Applications
Cut Stem or “Hack and Squirt” Treatments
Herbicides are a management tool that may be considered when other control measures have not been successful. Sometimes this control option provides the least amount of physical labor, low soil disturbance, and is more effective than other options. Pesticides can be overwhelming and intimidating, with misinformation and inaccurate “facts” being shared. If you would like to learn more about “mode of action” and how different herbicides are classified, check out this Herbicide Mode of Action link from Purdue.
A few questions that might help you determine if it’s time to explore herbicides as an option.
Have you tried mechanical or physical control options without success?
Would one application of herbicide save the soil on the site from being excavated, dug, or destroyed?
Always use the most appropriate chemical control option by finding the plant that you want to control on the product label and following the application instructions carefully.
Remember, with any pesticide (herbicide, insecticide, fungicide, rodenticide, etc.), the Label is the LAW! This is true even with organic pesticides.
The Environmental Protection Agency (EPA) is charged with approving, analyzing, and standing behind pesticides. Before approval, these herbicides are tested and labeled for use with specific instructions to minimize negative risk to yourself and the environment. Always use in accordance with the label and keep good records.
Herbicides that are commercially available to purchase have been tested to know the recommended rates and residual activity in soils and on micro/macro organisms. There are a lot of unknowns with homemade solutions, so homemade “remedies” are not recommended.
Invasive winged burning bush (Euonymus alatus). Photo: Rachel J. Rhodes, UME
Disposal of invasive plants
The last step in controlling invasive plants is proper disposal. Leftover plant materials can lead to potential accidental new infestations.
Proper disposal guidance:
Burn– If your county/city allows the burning of yard debris, be sure to follow all safety regulations and restrictions and do not breathe the smoke.
Pile– Fully dead/dried woody material that does not have seeds/fruits and is not covered in soil (which could allow it to sprout roots) can provide great nesting and shelter sites for wildlife- Read “The Value of a Pile of Sticks in Your Yard or Landscape”.
Dry or expose debris to intense heat– place debris in a black trash bag and let it “cook” for several weeks out in the hot sun, this will ensure that there are no viable seeds in the debris and all moisture is removed so that nothing can sprout. You can then add this to compost piles or dispose of it as you would “normal” landscape trimmings.
Check with your county/city government to find out if invasive plants should go in your yard waste or regular trash.
English ivy (Hedera helix)Heavenly bamboo (Nandina domestica)Yellow flag iris (Iris pseudacorus)
Let the particular plant that you are trying to control guide your management plan, and research the plant before you begin. Start control strategies on a small scale to see what works best and remember that many of the characteristics that led people to begin planting these invasives are the exact reasons that they are hard to control— some examples: wildlife resistance, good at spreading, breaking dormancy before natives early in the season. Also, keep in mind that many invasive species are a long-term fight and will require perseverance and, for best results, will require the use of different control tactics.
Lastly, once you successfully control the problem species, have a clear plan of what you will do with this space in your landscape. Installing new plants or keeping the area mulched will help prevent soil erosion or new infestations of weeds. Here is a list of recommended native plants for Maryland.
Everyone can help in the fight against invasive plants! Check the University of Maryland Extension website for an Introduction to Invasive Plants in Maryland and more information on how to reduce them. The absolute best way is to just never plant or introduce them into your landscape.
By Ashley Bodkins, Senior Agent Associate and Master Gardener Coordinator, Garrett County, Maryland. Read more posts by Ashley.
Plants that are used as ground cover can provide great services throughout the landscape as they can fill in areas that might otherwise be left bare or covered in mulch. Ground covers can be used to help reduce maintenance chores by preserving moisture and preventing weeds.
If you are looking for a ground cover plant, consider adding a native ground cover. Non-native ground covers and vines can be the plants of nightmares, as the characteristics that we like about them (aggressive, can take over weeds, need little care once established, etc.) are often the characteristics that make them terrible offenders when they escape into natural areas. A great field guide on this exact topic is Plant Invaders of Mid-Atlantic Natural Areas.
Since it’s prime planting season in Maryland, here I highlight three herbaceous plants that are often used as ground covers that can quickly take over. For a more detailed list of some of the other ground covers that are concerning, check out this webpage, Invasive Vines and Groundcovers.
English ivy (Hedera helix). Photo: M. Talabac, University of Maryland Extension
English ivy (Hedera helix) is sometimes just called “ivy” or “European ivy”, which reiterates the point that it is not a plant that is native to the United States. This evergreen, vining plant is one that you should be aware of as it can take over areas through the spread of seeds and through underground stems. It thrives in shade, is drought tolerant, and once established, it creates a thick, dense mat of foliage that can outcompete many perennials. It’s even been reported that it can damage homes/walls where it grows up and even penetrates the bark on living trees and strangles them. A study done in February of 2021 found that there are at least 5,000 trees in Takoma park could be lost because of English ivy. English ivy also serves as a reservoir for bacterial leaf scorch, a disease in maples, oaks, and elms.
Periwinkle (Vinca minor) close-up of purple flowers (left), and spreading along a staircase in Great Falls Park (right). Photos: M. Talabac
Periwinkle is a common plant that many people will recognize by its attractive shiny green leaves and purple-white flowers. There are actually two types, Vinca minor and Vinca major, unfortunately, both are considered invasive species and spread quickly vegetatively by root pieces (digging) and rooting at tips and nodes that contact the ground.
The third plant is bishop’s weed or goutweed (Aegopodium podagraria). Once established, this plant easily gets out of hand and is very difficult to remove. It is on the Maryland Department of Agriculture’s list of plants considered for regulation. Joyce Browning with the University of Maryland Extension in Harford County recently posted a video about bishop’s weed.
Remember that you can help mitigate the negative effects of invasive plants on local ecosystems by not adding them to your landscape. However, if you already have some of these plants, you can also manage them correctly by keeping them contained in certain areas and eliminating their spread into natural areas. Never place yard trimmings into natural areas, and remove the seeds before they can be spread by wind, rain, and/or animals. As you are adding plants to your landscape, please check out these great resources for non-invasive plant suggestions:
Everyone can help in the fight against invasive plants! Check the University of Maryland Extension website for an Introduction to Invasive Plants in Maryland and more information on how to reduce them. The absolute best way is to just never plant or introduce them into your landscape.
By Ashley Bodkins, Senior Agent Associate and Master Gardener Coordinator, Garrett County, Maryland. Read more posts by Ashley.
This is a guest post by Esther Bonney, a student in Charles County, Maryland, and a member of the University of Maryland Extension 4-H Program.
Invasive plants are detrimental to Maryland’s well-being, and their damaging effects are becoming more evident each year as we witness declines in crop productivity, reductions in pollinators critical to maintaining stable ecosystems, and widespread displacement of native habitats. Between 2008 and 2013, wild bees declined by 23 percent across the U.S.—a serious concern to farmers and consumers alike. Through educational programs, guides, and native giveaways, Nurture Natives is taking a stand against invasive species to protect native plants and pollinators, restore natural habitats, and support farmers. Nurture Natives is led by University of Maryland 4-Hers Esther Bonney and Samantha Rutherford and Extension 4-H Educator Amy Lang and UME Charles County Master Gardener Marlene Smith.
Visitors line up for native trees at Maryland Day, stretching down the courtyard and around the sidewalk, sometimes longer than the line for free ice cream!
In March 2022, our team was selected to attend the National 4-H Youth Summit on Agriscience. There, we developed our project, Nurture Natives, to address a prevalent agricultural issue in our community: invasive plant species. Invasive plants choke out native species and are a major cause of crop loss and food insecurity. Invasive trees such as the Tree of Heaven rapidly overtake farmlands and attract invasive pests such as the Spotted Lanternfly, which is a serious threat to grape crops. In the U.S. alone, invasive species cause $40 billion worth of production losses to crops and forests per year.
Nurture Natives is dedicated to increasing biodiversity through the planting of native trees and the eradication of invasive plants. In the past year, Nurture Natives has been featured on the National 4-H and University of Maryland Extension websites, won a Lead to Change Grant, and was selected by the National 4-H Council as one of two projects nationwide to receive the highly-competitive Scale for Success Award. Nurture Natives was also recently featured in the Southern Maryland Independent: Nurturing natives and the next generation of environmental scientists.
Our team began our work by educating and raising awareness about invasive species in our community of Charles County. We hosted educational programs at schools and camps and, in October 2022, partnered with eight local organizations to host the first annual Nurture Natives Giveaway. We hosted games, crafts, presentations, and a honey-tasting to showcase the importance of native species and pollinators. In just two hours, we distributed 150 native trees and shrubs and reached over 70 families.
Samantha Rutherford (left) hands out trees to visitors at Maryland Day, and Marlene Smith (right), Charles County Master Gardener, collects forms from patrons before they reach the tree distribution table.Continue reading →
Blooming flowers, emerging leaves, sprouting seedlings, and peeping frogs are just a few of the signs that encompass the magic of the spring season for me. As nature goes through the motions and awakens, I hope you have found some time to get outside and enjoy the wonderful gift of the changing seasons. Unfortunately, I’m always disheartened to see the number of invasive shrubs that are dotting the landscape this time of year. Spring is an easy time to see firsthand how invasive plants often break dormancy before native plants, which basically means that they leaf out earlier and have an automatic leg up as they are growing a few weeks before other plants. For more information, read Invasive Shrubs in Northeast Forests Grow Leaves Earlier and Keep Them Longer from Penn State.
Bush honeysuckle shrubs taking over a forest understory. Photo: Troy Evans, Great Smoky Mountains National Park, Bugwood.org
Q. What shrub has yellow-white (sometimes pink), trumpet-shaped flowers in mid-spring that smell sweet?
A: Exotic bush honeysuckle is a large category of several different fast-growing species (Lonicera maackii, L. morrowii, L. tatarica, L. xbella, L. fragrantissima) that are perennial, deciduous shrubs that can grow up to 20 feet in height. These species share many of the same characteristics — yellow to white, sometimes even pink-colored flowers, sweet-smelling flowers, and red to yellow berries in early summer. Leaves are opposite on the stem. Wildlife such as deer and birds are known to spread these invasive shrubs by eating the berries. If you look underneath utility lines or at the forest edge, you will often see these invasive shrubs.
As of February 2018, the Maryland Department of Agriculture classified Amur honeysuckle (Lonicera maackii) as a Tier 1 invasive plant in Maryland. A person may not propagate, import, transfer, sell, purchase, transport, or introduce any living part of a Tier 1 invasive plant in the state. For more information visit the University of Maryland Extension page about Exotic Bush Honeysuckles. For control information, visit Invasives In Your Woodland: Bush Honeysuckles.
Bush honeysuckle flowers. Photo: Ryan Armbrust, Kansas Forest Service, Bugwood.orgRed fruits of bush honeysuckle. Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Over the last 5 years, I’ve seen a huge increase in the number of invasive shrubs in my own woodlot, which is secluded from homes due to the mountainous terrain. Nonetheless, Japanese Barberry (Berberis thunbergii) has begun taking over the understory and edges of hayfields. I believe that it was spread by wildlife. Did you know this shrub gets small yellow flowers in early spring and then red berries?
Japanese barberry flowers are yellow. Photo: Miri Talabac, University of Maryland ExtensionJapanese barberry fruits. Photo: Richard Gardner, Bugwood.org
Q. I see Japanese barberry planted in many landscapes. Is it really an invasive plant?
A: This invasive shrub has been used in landscapes in North America since the late 1800s. It is very popular because it provides resistance to deer browse and can grow in a wide variety of light and soil conditions, making it a plant that can be used dependably in home landscapes. However, these characteristics contribute to its aggressive nature when spreading into natural areas. It forms dense foliage thickets that create an ideal humid environment for black-legged ticks (deer ticks) which can carry the pathogen that causes Lyme disease.
The Maryland Department of Agriculture (MDA) has named this a Tier 2 invasive plant. This classification means retail stores that offer this plant for sale must display a required sign indicating that it is an invasive plant. Landscapers may not supply Japanese barberryunless they provide the customer with a list of Tier 2 invasive plants. In our neighboring state of Pennsylvania, Japanese barberry is on the noxious weed list and will be banned for sale beginning this fall.
Japanese barberry infestation in a forest. Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Q. I want to add a shrub to my landscape that provides berries for the wildlife and fall foliage color. Is burning bush (Euonymus alatus) a good choice?
A: Unfortunately, winged burning bush (Euonymus alatus) is not the best choice when adding a new shrub to your landscape, as the Maryland Department of Agriculture (MDA) has named this a Tier 2 invasive plant. This classification means retail stores that offer this plant for sale must display a required sign indicating that it is an invasive plant. Landscapers may not supply winged burning bushes unless they provide the customer with a list of Tier 2 invasive plants. It is also important to note that burning bush is now a banned noxious weed in our neighboring state of Pennsylvania.
Burning bush branch. Photo: Richard Gardner, Bugwood.orgBurning bush fruits. Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Q. Does Heavenly bamboo support wildlife with its evergreen leaves and red berries?
Heavenly bamboo, sacred bamboo, or Nandina (Nandina domestica) has berries that are actually toxic to cats and also cedar waxwing birds. This plant was introduced from Asia in the early 1800s but it outcompetes many native plants with its aggressive nature.
MDA has named Nadina a Tier 2 invasive plant. This classification means retail stores that offer this plant for sale must display a required sign indicating that it is an invasive plant. The Nandina cultivar ‘Firepower’ is the only exception.
Invasive heavenly bamboo (Nandina domestica). Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
All of these invasive shrubs produce berries which is one of the ways they spread so widely and easily. Please research plants before adding them to your landscape. Below are links for information on finding non-invasive plants:
Last month, my blog post was an introduction to invasive plants and today I want to share information on three invasive, deciduous trees found in Maryland.
Springtime provides a breathtaking display of contrasting flowers in a wide array of colors, shapes, and sizes, which are found in herbaceous plants, as well as woody shrubs and trees. Unfortunately, some of these spring flowering trees are invasive and you need to be aware of their negative effects on ecosystems such as competition for resources including sunlight, soil nutrients, and space.
Q: What medium-sized invasive tree has white blooms in the early spring in Maryland?
Callery pear (Pyrus calleryana) in flower. Photo: Britt Slattery, US Fish and Wildlife Service, Bugwood.org
Callery Pear (Pyrus calleryana), sometimes referred to as ‘Bradford’ Pear, has several cultivars including ‘Chanticleer,’ ‘ Cleveland Select’, and ‘Autumn Blaze’, all of which will be in bloom around this time of year. The Callery pear was imported from Asia to Maryland with the hope of being able to help edible Bartlett pears, which were being threatened by a disease called fire blight. The plan was to cross these pears to gain disease resistance in the pear industry. Unfortunately, this experiment was unsuccessful in preventing fire blight, but these crosses seemed to have potential for the ornamental industry and were planted widely. Bloom time often coincides with our native serviceberry, which produces white flowers too.
The ‘Bradford’ cultivar was thought to be sterile; however, when new cultivars of Callery pear were developed, it was able to cross-pollinate with those and produce viable seeds. Birds and other wildlife eat the fruits, which results in spreading them to different areas. The seeds sprout and grow into dense thorny thickets, which are very difficult to control and result in crowding out native vegetation. Callery pear provides a stunning show of beautiful white blossoms; unfortunately, these trees are highly invasive, which has led a few states to ban all cultivars of Callery pear (Pennsylvania, Ohio, and South Carolina). This tree has an attractive V-shaped crotch that unfortunately will often split from high wind and snow weight damage.
For more information, history, and control options, please visit the University of Maryland Extension webpages: Invasives in Your Woodland and Bradford Pear.
Q: What invasive tree has purple blooms in early spring?
Princess Tree (Paulownia tomentosa). Photo:Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Paulownia (Paulownia tomentosa), also called princess tree or empress tree, has purple, pleasant-scented blooms that appear before the foliage in early spring. I saw this tree for the first time when I traveled to Howard County for training in 2012, as this is not a tree we have in Garrett County. Its striking, large, heart-shaped leaves automatically caught my attention and reminded me of the Northern catalpa tree, a great native tree that should not be mistaken for Paulownia. According to Plant Invaders of the Mid-Atlantic Areas, one empress tree is capable of producing 20 million seeds that mature to flowering in only 10 years! These trees prefer full sun but can grow on disturbed soils, creek banks, and even forested areas which gives them a big advantage over native species that often require more special environments to grow and thrive. Paulownia’s ability to sprout from adventitious buds on stems and roots allows it to survive fire, cutting, and bulldozing. It is, therefore, a very difficult and costly invasive plant to control, according to the Maryland Invasive Species Council Plant Invader of the Month listing.
A great alternative to Paulownia is the native Eastern redbud, which produces early, purple/reddish-purple blooms.
For additional information, history, and control options for Paulownia, visit the University of Maryland Extension web pages Invasives in your Woodland and Princess Tree.
Q: What invasive tree looks similar to black walnut?
Tree-of-Heaven (Ailanthus altissima). Photo: Chuck Bargeron, University of Georgia, Bugwood.org
Tree-of-Heaven (Ailanthus altissima) was introduced in the late 1700’s and thrives in many soil conditions. It has an amazing ability to grow very quickly and can disturb building foundations and even pavement! It was widely planted as a street tree and thus is found far and wide in the Eastern United States. This tree is called by other names including China-sumac, stinking sumac, or varnish tree due to its strong unpleasant odor. Tree-of-Heaven is sometimes mistaken for sumac, hickory, or black walnut because of similarities in leaf shape; however, look for the glands on the bottom of each leaflet to confirm its identity.
Just in case you needed one more reason to remove Tree-of-Heaven, it is a preferred food source for the new, exotic, invasive insect pest, spotted lanternfly.
For more specific information, history, and control options, visit these web pages:
Keep an eye out this spring for non-native, invasive trees as there are many others that I did not address in this article. Take any opportunity to help educate friends or family about the negative impact of invasive plants on biodiversity.
It’s a sunny day in late February and that means I’m looking at seed catalogs and dreaming of new plants! Have you been plant shopping yet this year? Adding new plants and seeds to your garden creates new scents, textures, colors, and shapes and is the easiest way to increase biodiversity in your landscape!
As you begin revitalizing your garden space this spring, I want to bring some attention to invasive plants, a category of plants that should strike fear and dread in your heart! Okay, maybe that’s a bit dramatic, but truly this is a topic that everyone needs to learn more about.
Q. What is an invasive plant?
A. An invasive plant is a non-native, “alien” species that was introduced intentionally or by accident into the landscape and causes ecological and/or economic harm. These plants tend to be free from predators, parasites, and diseases that could help keep them in check. These plants reproduce rapidly with multiple methods (i.e. seeds, stolons, root cuttings, runners, etc.) and spread aggressively. They tend to be deer resistant or deer tolerant, a big reason why they are purchased and planted in landscapes. Below is a photo of purple loosestrife. Notice how it is creating a monoculture, a visual key that might mean the plant is “invasive.”
Invasive purple loosestrife (Lythrum salicaria). Photo: Richard Gardner, Bugwood.org
Did you know that some invasives are still for sale at nurseries, greenhouses, and in mail-order catalogs?
It’s true. Many of the plants on “watch lists” are still readily available to purchase. Japanese barberry is an invasive plant that is a very popular landscape plant still being widely planted today; however, research shows that black legged ticks have been found in areas with invasive barberry thickets because these non-native, invasive forest shrub thickets create ideal microclimates.
