invasive plants

Invasive Ornamentals and Sterile Varieties

Maryland Grows3 Comments

When it comes to landscaping, a huge decision-making point is what we find visually pleasing… and often what pleases us visually ends up being something we are not very used to seeing, meaning that we pick plants that seem more exotic to us so we can marvel at their surprising (to us) beauty. This is all good and nice, but the problem appears when we realize that many of those plants appear exotic to us because they are exotic to the region we live in! This means that if we select them to plant in our landscapes, we are actually adding to our environment species that are not necessarily native to where we live… which can have pretty drastic consequences. In today’s post, I want to talk about a potential solution that has fairly recently been proposed to the use of such plants: sterile varieties.

What’s the deal with exotic plants?

Although not all exotic plants will have negative effects on our environment, some of them do. Those that do are considered invasive species, and they can create a lot of trouble in our local ecosystems. Invasive plants tend to grow faster than other native plants, often overrunning the spaces they grow in, spreading very quickly, and eventually “choking” or outcompeting local species, which end up dying out and/or becoming unable to survive in the presence of the invasive plant. Some good examples of this behavior of invasive plants in Maryland are the Chinese and Japanese Wisteria vines and the English Ivy, all of which effectively cover trees and can eventually choke and pull them down to their death.

View of a forest with vines covering the tree trunks up into the canopy.
In the Eastern USA, English Ivy does effectively take over forests. Photo: L. J. Mehrhoff.

In Maryland, this issue has been recognized not just by ecologists, but also by lawmakers, who have started to regulate the selling of specific species to properly support the protection (and recovery) of our local plant communities. Among the most recent additions to these regulations are the ban on selling several bamboo species, English Ivy, exotic Wisterias, and several very invasive grasses (among other species). You can check the most up-to-date list of these species at the Maryland Dept. of Ag. website: Maryland Prohibited Invasive Plant Law and Regulations. The Maryland Department of Natural Resources also hosts a website with a lot of information about exotic species (plants and others): Invasive and Exotic Species in Maryland

So what to do if we love the plants but do not want them to spread?

Ideally, if we do not want to harm local habitats, the best decision is to refrain from planting invasive species, because they are REALLY hard to properly control and prevent their spread (especially when there is bird-mediated fruit dispersal or stolon-mediated dispersal).

The forest in spring with many mature trees and Barberry invading the understory and dominating as the ground cover
Barrberry dominating the understory in a wooded setting. Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Bright red berries the shape of water drops hang along barberry branch.
Barberry shrubs produce many berries that birds and wildlife eat then distrubute. Photo: Chris Evans, University of Illinois, Bugwood.org

An alternative, however, is the selection of varieties that are unable to spread because they are sterile or do not have proper structures to do so. These are varieties that exist for some ornamentals/exotics, and that are in some cases exempted from the regulations that I was mentioning above. Some examples are non-invasive bamboo varieties, some Berberis cultivars (e.g., varieties “Lemon Glow”, “Crimson Cutie”), and even some almost-sterile Buddleja cultivars (e.g., “Flutterby”, “Lo and Behold” varieties developed by several University programs). A note on some of these cultivars is that although some of them are labeled “sterile”, they may or may not be fully sterile. Some of them have indeed been shown to, in some cases, produce some fertile offspring (although way fewer than their fertile counterparts!).

A green field with a forest line in the background. Purple wisteria vines are growing up many trees and shrubs, toppling one over.
Invasive Wisteria invades forests, vining themselves onto trees, pulling them down and eventually outcompeting and often killing them. Photo: M. Bakacs.

How to go about these decisions?

Generally, when considering exotic ornamentals for our green spaces, it is worth making it a practice of first informing ourselves about their potential for invasiveness. Then, if the potential is there, another good practice is to look for potential alternatives (e.g., do we really need to plant that specific plant?, are there less-harmful varieties?, are there native alternatives that can be planted instead?, can we properly contain the plant if it spreads?).

To make these decisions, a good tool to consider is the NC Extension Gardener toolkit, where species and varieties are listed and can be filtered out by (among other traits) their potential for invasiveness/weediness. The Maryland Invasive Species Council has also put together a list of species that have invasiveness potential (independently of regulations) and are thus of concern. A new tool from the University of Maryland Extension Maryland Native Plants Project can help you search and filter for native plants, so you can potentially choose a native plant which will suit your needs and benefit our eco-system: Maryland Native Plant Finder tool.

By Anahí Espíndola, Associate Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

Have You Seen Incised Fumewort?

Maryland Grows1 Comment
two-toned lavender flowers of incided fumewort
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.

volunteer uses a mobile photo to document invasive incised fumewort displacing VA bluebells

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.

If you would like to read more about incised fumewort biology, a native look-alike, and making iNaturalist reports, check out this article by the National Park Service.

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.

Getting Rid of Invasive Plants: Solarization, Smothering, Repeated Cutting, Herbicides?

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Asian honeysuckle has white flowers
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: 

  1. 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.
    1. Is the plant a woody perennial, herbaceous perennial, or annual? 
    2. Has the plant been a problem for several years in your landscape, or is it a relatively new concern? 
  2. 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.  
  3. If controlling 100% is not a feasible option, determine how you can prevent the plants from spreading or allowing them to get stronger. 
  4. 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. 
  5. 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.
purple and blue berries of invasive porcelainberry vines
Invasive porcelain-berry vines (Ampelopsis glandulosa var. brevipedunculata). Photo: Rachel J. Rhodes, UME

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:

  1. Pulling  and digging.
  2. Suffocation or smothering with landscape fabric, mulch, cardboard, multiple layers of newspaper, anything to block the sunlight and prevent the plant from growing.
  3. Solarization: laying plastic over the plants to “cook” live plants and viable seeds with the heat that builds up underneath. 
  4. 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

  1. Foliar Applications
  2. 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. 

  1. Have you tried mechanical or physical control options without success? 
  2. Would one application of herbicide save the soil on the site from being excavated, dug, or destroyed?  
  3. 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.
  4. Remember, with any pesticide (herbicide, insecticide, fungicide, rodenticide, etc.), the Label is the LAW! This is true even with organic pesticides. 
  5. 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.
    1. 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: 

  1. 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.
  2. 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”. 
  3. 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.
  4. 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. 

Additional resources: 

Removing Invasive Plants and Planting Natives in Maryland – University of Maryland Extension

(PDF) Managing Invasive Plants: Methods of Control – New England Wildflower Society

(PDF) Guidelines for Disposal of Terrestrial Invasive Plants – University of Connecticut

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.

Non-Native Plants Support Non-Native Mosquitoes

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It is a common misconception that all mosquitoes feed on blood. Unlike ticks, which require a bloodmeal to progress from one life stage to the next, mosquitoes largely rely on plants throughout their life cycle. Only adult female mosquitoes bloodfeed in order to acquire protein to lay eggs; otherwise, adult mosquitoes feed on plant sugars to gain energy for flying, mating, and metabolic demands. Once those eggs are laid in standing water, mosquitoes hatch as aquatic larvae that eat microbes supported by decaying organic matter, called detritus. This detritus often comprises plant parts like leaves, seeds, and fruits that fall from nearby vegetation into larval habitat. The next life stage before adulthood, the pupa, is non-feeding, so the amount and quality of detritus mosquitoes receive as larvae are crucial. Just like we tell children to drink their milk to grow up to be big and strong, mosquito larvae with plentiful and nutritious resources can reach adulthood faster, grow larger, live longer, and lay more eggs as adults. Yikes! 

life cycle of a Aedes mosquito from adult to egg to larva to pupa
Aedes mosquito life cycle.
Image credit: Centers for Disease Control and Prevention

Leaves may vary drastically in their chemical composition, affecting which microbes they support, how quickly they decay, and what beneficial nutrients or toxic secondary metabolites they release as they decompose. Researchers are still working to identify important traits in a detritus resource base, but a trend has emerged: non-native plants seem to support non-native mosquito populations better than native plants do.

Native species, whether plant, animal, or microbe, are those that occur naturally in the region where they evolved. Over the course of time, these species have adapted to the local environment and developed relationships with other native species. Conversely, non-native species are those which evolved in a different region from that in which they can now be found. A small percent of non-native species establish and spread rapidly throughout their new home, with the potential to harm human well-being, environmental health, and/or economic prosperity. Some researchers speculate that non-native species share certain traits that make them successful invaders. The Asian tiger mosquito, Aedes albopictus, is one of the most successful invaders of the past century, arriving in Texas from Asia in 1985 and reaching us here in Maryland by 1987. The tiger mosquito is capable of spreading viruses such as dengue, West Nile, and zika; it is also a nuisance vector, driving people indoors with its aggressive daytime biting behavior. 

asian tiger mosquito larva
asian tiger mosquito
An Asian tiger mosquito (Aedes albopictus) larva [left] and female adult [right].
Photo: Ary Farajollahi, Bugwood.org
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Select Ground Covers for Your Landscape Carefully

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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.

a covering of English ivy under a tree
near a forest edge English ivy is all over the ground and climbing up trees
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.

For more information on English ivy, visit these webpages from the University of Maryland Extension: English Ivy and Invasives in Your Woodland.

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.

It can be overwhelming when considering adding plants in troubled areas. A great resource for ideas is the University of Maryland Extension webpage about Lawn Alternatives. 

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: 

Landscaping with Native Plants- Maryland Native Plant Society 

Keystone Plants by Ecoregion- National Wildlife Federation

Resources on invasive plant identification: 

Plant Invaders of the Mid-Atlantic Natural Areas (PDF)

Do Not Sell! Ornamental Invasive Plants to Avoid with Climate Change (PDF)

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.

Invasive Trees in Maryland: Princess Tree, Callery Pear & Tree-of-Heaven

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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?

invasive callery pear trees crowded along a road
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?

lavender flowers of princess tree

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 foliage looks very similar to that of black walnut and sumac
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.   

Resources for invasive plant identification: 

Resources for non-invasive plant suggestions: 

Check out the University of Maryland Extension website on Introduction to Invasive Plants for more information on how to reduce invasive plants.

Remember, the absolute best way to avoid invasive plants is to 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.

Plant shopping soon? Avoid buying invasive plants

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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.”

purple loosestrife flowers crowding a field
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.   

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