forest overgrown with invasive plants

A lot teeming with foreign invasive plants like Callery pear, English ivy, autumn olive, and Japanese honeysuckle
Photo: M. Boley

Updated: June 23, 2021

Key points

  • Invasive plants are not native and harm the environment, economy, and even human health.
  • Invasive plants can be controlled long-term by utilizing a combination of control techniques and tools that are specific to their biology.
  • Replace invasive plants with competitive native plant species that are appropriate for the soil and growing conditions  (Refer to: Table 1)

What are invasive plants and why should they be removed?

Invasive species are non-native organisms that cause harm to the environment, economy, or human health with damages costing the United States approximately $120 billion every year (Simberloff, 2013). Invasive plants alter the native ecosystem and disrupt biodiversity in forests, meadows, and wetlands. These species have unfair advantages over native plants, especially in human-disturbed habitats. They reproduce aggressively in multiple ways, and at a much faster pace than our indigenous plants. 

Why should communities and residents be concerned about invasive plants?

Invasive plants are the greatest threat to our natural environment, other than habitat destruction. Our native environment supports native plant biodiversity crucial for the survival of insect and bird populations and the entire food chain. Invasive plants also cost our national economy billions of dollars annually, devastate agriculture, and diminish the quality of parks, natural, and recreational areas. 

For more information on how invasive plants impact ecosystems, refer to our Invasive Species resource page. For information regarding the retail sale of invasive plants, please visit the Maryland Department of Agriculture Invasive Plant Control page. Visit the Maryland Invasive Species Council website to find a representative list of invasive species in Maryland. For a complete list of species and their degree of concern, consult the Mid-Atlantic Invaders Tool.

The term ‘native’ refers to a plant species that occurs naturally in an ecoregion and habitat over the course of evolutionary time. To learn more about native plants, please refer to What is a Native Plant?

Controlling invasive plants long-term 

Because of the aggressive nature of invasive plants, it is unlikely that one treatment will completely eradicate a population. Unless control methods are used before establishment, it may take months to years of observation and management to suppress new growth of the undesired plants.

We recommend a methodical approach to management:

  • Identify the problem, 
  • Learn more about the plants’ biology,
  • Utilize a variety of control methods and tools to eradicate, 
  • Replace the area with competitive plantings, and 
  • Continue to monitor the area and take action as needed.
  1. Proper plant identification is the first step to invasive plant control. Before implementing any methods, consult HGIC’s Ask Extension or contact your local county Extension office
    1. Use the Invasive Species page to find common invasive woody and herbaceous plant species in Maryland.
    2. Early detection and eradication are best when plants are smaller or more manageable. Taking any early action will help slow the spread. Any action, any time, can have a profound impact stopping invasives. 
  2. Understanding the biology and growing habits of an invasive plant species will help you create an implementation plan for successful control. 
    1. (PDF) Plant Invaders of Mid-Atlantic Natural Areas provides great guidance for how to approach control and handle the species in question.
    2. Recognize your challenges; if a neighbor has English ivy or Callery pear, you’ll want to identify those plants as needing more attention for removal. Better yet, convince your neighbors to join the effort in eradicating their invasive plants too!
  3. Use a variety of control methods as part of a “toolbox” approach; physical and mechanical removal, biological control (rare), and chemical control as a last resort. 
    1. Some common mechanical treatments include repeat mowing, pulling, smothering with cardboard/newspaper/wood chips, cutting, or livestock grazing. Mechanical removal is recommended for small spaces.
    2. Chemical control can include different methods: cut stump, “hack and squirt”, basal bark, and foliar applications. The treatments are different depending on the species, so it is important to understand the plant’s biology and growth habits. It is highly recommended to use (PDF) Plant Invaders of Mid-Atlantic Natural Areas as a guiding resource, or HGIC’s web pages.
    3. Invasive Grass Control
    4. Invasive Herbaceous Plant Control
    5. Invasive Shrub Control
    6. Invasive Vine and Groundcover Control
  4. Replace the area with native plantings as soon as possible. Exposed or disturbed areas can easily be taken over again by the invasive species you have worked so hard to remove. Here are some ideas and recommendations to consider:
    1. If the space is small enough, homeowners may choose to remove all undesirable plants at one time.
    2. With larger spaces or wood lots, homeowners may choose to address the area in manageable sections or prioritize spaces for removal effort. For example, a homeowner may choose to remove Japanese barberry from the existing landscape to replace it with a native alternative, such as Virginia sweetspire.
    3. Even without funds to purchase replacement plantings, small efforts to control invasive plants can have a big impact. For example, cutting out a 12” section of English ivy vine that is growing up the trunk of a large landscape tree. For better efficacy, it would be recommended to paint the cut ivy surface with glyphosate or another herbicide approved for woody vine control.
    4. Please refer to the Recommended Native Plants (Table 1) section below for specific species to plant.
  5. Even after initial removal efforts, continue to observe and suppress invasive plant growth as it returns. Monitor the area as you participate in replanting, and spot-treat as necessary. Use different methods of control and treatments depending on the time of year, plant species, and severity of invasion.

A comment on the use of pesticides personal protective equipment (PPE)

When used properly and according to the label, herbicides are a very effective tool in the removal of alien plant species. It is recommended you wear proper PPE to protect yourself. Also, familiarize yourself with information about using glyphosate and alternatives as a control method.

Replacing invasives with recommended native plants

In order to compete with the growing habits of invasive plants, it is recommended you choose native species that can be considered “aggressive”. It is crucial to consider growing conditions and soil type when you choose replacements.

Bee balm (Monarda) is spreading in a bare area where invasive where removed
Widespread bee balm, (Monarda didyma), popping up in early spring.
From 2 transplants, the area is now dominated by the plant only 1.5 years later.

 

native plant lyre leaf sage growing in a bare area
A carpet of lyre leaf sage seedlings, (Salvia lyrata)

Can native plants be invasive?

The term “invasive” is usually in reference to an alien species that has been introduced to an area. That is why native plants are referred to as “aggressive” instead. Some of these species are too overwhelming for a small or tidy landscape but may work perfectly in the battlegrounds of disturbance.

Table. 1: Competitive Native Plants to Replace Invasives
Plant Type Common Name Botanical Name Full Sun/Part
Shade/Full
Shade
Soil (Clay, Loam,
Sand)
Moisture (Dry, 
Moist, Wet)
Attributes
Grass/Grass-like Switchgrass Panicum virgatum S, PS C,L,S D, M, W Deep root systems, stabilizer of soils. Can occur in both fresh and brackish marshes. Considered aggressive for small home gardens.
Grass/Grass-like Wool rush Scirpus cyperinus    S C,L,S M, W Grows in tough clumps- great for ditches and wet areas, will spread. Good for rain gardens and ditches. Host for Dion skipper and Eyed brown butterflies.
Grass/Grass-like Northern sea oats Chasmanthium latifolium   PS C,L,S D, M Self-seeds readily by attractive seed heads. Will handle some shade.
Perennial Boneset Eupatorium perfoliatum S, PS, Sh C,L,S M, W Floodplains and ditches - huge pollinator attractor! Interesting coarse texture in the landscape. Good for conservation and rain gardens as well.
Perennial Blue mistflower Conoclinium coelestinum S, PS, Sh C,L D, M, W Belongs to mint family- will wander if allowed. Great for meadows, damp woods. Vibrant violet flower. Not deer resistant.
Perennial Sensitive fern Onoclea sensibilis S, PS, Sh C,L,S M, W Spreads by underground runners- good groundcover, but will range. Deer resistant.
Perennial Golden ragwort Packera area S, PS, Sh    L M, W Boasts a long bloom time. Can be aggressive- prefers wetland/moist bottomland areas.
Perennial Cutleaf coneflower Rudbeckia laciniata S, PS C,L,S M, W Tall, herbal uses. Will spread in wet areas and ditches. Tolerates acid soils
Perennial Lyre-leaf sage Salvia lyrata S, PS L, S D, M Great groundcover- will self-seed freely. Can handle deep shade, prefers sun. Will bloom twice (spring and fall) if deadheaded.
Perennial Canadian goldenrod Solidago canadensis S, PS C,L,S D, W Seen commonly in fields, roadsides, fallow spots. Good late-season source of nectar/pollen
Perennial Mountain mint Pycnanthemum spp. S, PS Depends on
species
Depends on
species
Great for pollinators - P. incanum will handle shade, but most prefer sun. Spreads vegetatively.
Perennial Canadian germander Teucrium canadense S, PS C,L,S    M Plants spread by rhizomes and prefer moist soils. Makes great cut flower and ground cover.
Perennial Bee balms Monarda spp. S, PS Depends on
species
Depends on
species
Showy flowers. Belongs to the mint family. Great for pollinators.
Perennial Common milkweed Asclepias syriaca    S L,S    D Once established, will build colonies of milkweed. Can tolerate the tough soil found on the shoulders of roadways. Great for monarchs and other pollinators.
Perennial White snakeroot Ageratina altissima S, PS, Sh C,L,S D, M A tough plant that prefers basic soil types.
Annual Orange jewelweed Impatiens capensis PS, Sh C,L,S M, W Annual that competes well in areas populated by Japanese stiltgrass. Prefers moist bottomlands with shade.
Shrub Groundsel Baccharis halimifolia    S C,L,S D, M, W Dominates ditches and shoreline sites- tolerates flooding and salinity, alkaline sites.
Shrub Elderberry Sambucus canadensis S, PS, Sh C,L,S M, W Edible berries (human & wildlife), suckers, prefers alkaline soil, best in swamps.
Shrub Summersweet Clethra alnifolia PS, Sh C,L,S M, W Very fragrant flowers- tolerates some salinity, suckers freely.
Tree Sweetgum Liquidambar styraciflua S, PS C,L,S M, W Wetland tree - can dominate wetland areas. Seeds contain shikimic acid (medicines)
Tree Loblolly pine Pinus taeda S, PS C,L,S D, M, W Evergreen, winter cover, food for wildlife, acidic conditions. Early successional.
Tree Eastern red cedar Juniperus virginiana    S C,L,S D, M Fruit supports over 50 bird species - self-seeds readily. Alternate host for Cedar-Apple rust.
Tree Boxelder Acer negundo S, PS C,L,S M, W Grows in lowlands next to rivers or waterways. Tolerates a variety of soils. Wood is considered brittle.
Vine Virginia creeper Pathenocissus quinquefolia S, PS, Sh C,L,S D, M, W Bank stabilizer - can be used as groundcover. Trim to control as needed. Great fall color.
Vine Trumpet vine Campsis radicans S, PS C,L,S D, M Very thick vines - try to keep off trees to avoid dragging or breaking branches.
Vine Native honeysuckle Lonicera sempervirens S, PS C,L,S D, M Flowers a long time, attractive color. Very beneficial for wildlife. Grows less wildly than the Japanese species. Needs a vertical surface or trellis.

 

Additional resource 

Book | Simberloff, Daniel. (2013) Invasive Species: What Everyone Needs to Know.

Author: Mikaela Boley, Senior Agent Associate in Home Horticulture, University of Maryland Extension, 5/2021