The Tiers Of Invasive Plants In Maryland: A Growing Concern

In the picturesque landscapes of Maryland, a battle is brewing beneath the surface, one that threatens the state’s native ecosystems. Invasive plants, often introduced unintentionally, have taken root and flourished, disrupting the delicate balance of local flora and fauna. The state’s Department of Natural Resources (DNR) classifies these invasive plants into different tiers, reflecting the level of concern they pose to Maryland’s environment. This article will explore the tiers of invasive plants in Maryland, highlighting specific varieties and their impact on the local ecosystem.

Japanese Honeysuckle (Lonicera japonica)
Japanese Honeysuckle (Lonicera japonica)

Tier I: Severely Invasive

The highest level of concern, Tier I invasive plants, includes species that significantly threaten Maryland’s native habitats. One notorious member of this tier is the Japanese Honeysuckle (Lonicera japonica), known for its aggressive growth and smothering of native vegetation. Another, the Mile-a-Minute Vine (Persicaria perfoliata), lives up to its name by rapidly covering entire areas with its dense foliage, outcompeting native plants for sunlight and resources. Tier I invasive plants cannot be offered for sale in any nursery or Garden Center. 

Tier II: Moderately Invasive

Tier II includes invasive plants of moderate concern, which, while not as destructive as Tier I species, can still have a negative impact. The Tree of Heaven (Ailanthus altissima) is a prime example, known for its rapid growth and ability to take over open spaces. This tree disrupts forest ecosystems and produces chemicals that inhibit the growth of nearby plants. Another Tier II plant, the Butterfly Bush (Buddleja davidii), though prized for its attractive blooms, can crowd out native plants and reduce biodiversity. Tier II invasive plants can be offered for sale provided the seller posts signs notifying the public of their Tier II invasive status. 

Tier III: Watch List

The lowest tier of concern, Tier III, encompasses species that have the potential to become invasive but are not currently widespread in Maryland. The Callery Pear (Pyrus calleryana), often planted for its ornamental value, is on this watch list due to its invasiveness in neighboring states. If left unchecked, these plants may establish themselves more firmly in Maryland, warranting increased monitoring and management efforts. No regulations are applied to Tier III invasive plants.

Butterfly Bush (Buddleja davidii)
Butterfly Bush (Buddleja davidii)

Impact on Local Ecosystems

Regardless of their tier, invasive plants in Maryland disrupt the natural balance of local ecosystems. They outcompete native vegetation, reducing biodiversity and altering the habitat for native wildlife. Some invasive plants, like the Japanese Barberry (Berberis thunbergii), provide suboptimal food sources for local wildlife, further impacting the delicate web of life in Maryland’s forests and wetlands.

The tiers of invasive plants in Maryland are valuable for assessing and prioritizing management efforts. To protect the state’s native ecosystems, it’s crucial to remain vigilant, identifying and managing invasive plants before they become entrenched. By understanding the threat posed by each tier, Maryland can work towards a healthier, more resilient environment where native flora and fauna thrive.

A full list and the regulation regarding invasive plants is available HERE:

Barberry (Berberis thunbergii)
Barberry (Berberis thunbergii)

Invasive Plants In The Landscape

Gardening enthusiasts often find themselves in a dilemma when it comes to incorporating plants labeled as invasive into their landscapes. Plants like Barberry (Berberis thunbergii), Miscanthus (Miscanthus sinensis), and Buddleia (Buddleja davidii) are known for their attractive features but also have a reputation for potentially escaping into the wild. However, with careful planning and responsible gardening practices, it’s possible to enjoy the beauty of these plants without contributing to their invasive spread.

Understanding The Risks

Before adding any potentially invasive plant to your landscape, it’s crucial to understand the risks associated with its cultivation. Invasive plants often thrive in disturbed environments, where they can outcompete native species and disrupt local ecosystems. They can also escape from gardens into nearby natural areas, leading to ecological imbalances. Therefore, weighing the benefits of these plants against the potential risks is essential.

Choosing Non-Invasive Varieties

One way to enjoy invasive plants without harming the environment is to select non-invasive or sterile cultivars. Plant breeders have developed many sterile varieties that retain the desirable characteristics of the parent plant without producing viable seeds. For instance, some Barberry cultivars, like Berberis “worry-free” Crimson Cutie, are sterile, non-invasive, and safe for landscaping. By choosing these alternatives, you can enjoy the plant’s aesthetics without worrying about it spreading uncontrollably.

There are also sterile varieties of Buddleia on the market today, such as the Flutterby series and the Low and Behold series from Proven Winners. Miscanthus ‘Bandwidth,” which was bred by NC State, has proven to be sterile and safe for planting in the landscape. 

Callery Pear (Pyrus calleryana)
Callery Pear (Pyrus calleryana)

Responsible Maintenance

Responsible gardening practices play a crucial role in preventing the spread of invasive plants. Regularly monitor your landscape for any signs of escape, such as self-seeding or aggressive spreading. If you notice such behavior, promptly remove the offending plants to prevent further spread. Also, avoid disposing of invasive plant material in natural areas, which can contribute to their colonization.

Another trick to preventing invasive species from spreading is removing the spent flowers before the seed heads mature. This is especially easy on plants like butterfly bush.

Containment and Barriers

For particularly aggressive species like Miscanthus, consider containment methods. Planting them in containers or using root barriers can help restrict their growth and prevent rhizomes from spreading. This allows you to enjoy their ornamental features without the worry of unchecked expansion.

Native Plant Companions

Another strategy is to surround potentially invasive plants with native species. Native plants are well adapted to the local ecosystem and can often outcompete invasives. By creating a buffer of native vegetation around invasive plants, you can help minimize their impact on the environment.

Gardening with potentially invasive plants like Barberry, Miscanthus, and Buddleia is possible when approached with care and responsibility. By selecting non-invasive varieties, practicing vigilant maintenance, and using containment methods, you can enjoy these plants’ beauty while minimizing their ecological impact. Remember that responsible gardening benefits your landscape and helps preserve local ecosystems.

This Post Has One Comment

  1. L. Elliott Reply

    Good article about invasive plants. (I still love my butterfly bushes, but I know why they have been added to the list.) Thank you for stocking many native plants and helping to highlight their importance.

Leave a Comment

Your email address will not be published. Required fields are marked *