Invasive Species of Haverhill

What is an invasive plant?

Invasive plants are non-native plants that spread rapidly and colonize foreign landscapes, causing significant economic and ecological damage. Invasive plants are often identifiable by large, dense "weedy" thickets of a single plant species, called a monoculture, and a notable lack of native plants. 
The most common way invasive plants are introduced is through horticulture. Close to 82% of invasive woody plants were ornamentals that escaped from cultivation. Once an ornamental becomes invasive, there is nothing to prevent it from spreading. Non-native plants lack the plant-insect relationships of native species that have evolved over millions of years. Up to 90% of insect species only feed on plants in a single family and most mammalian herbivores, including White-tailed deer, show an aversion to foraging non-native plants. With no predators, non-native plants can spread 'unchecked'.

Why manage invasive plants?

Invasive plants negatively impact both human and natural communities in a number of ways:

Natural Communities

• Many invasive plants release allelopathic phytotoxins into soils, depriving other plants of necessary nutrients
• Invasive plants reduce insect pollinator habitat and, in some cases, can poison them, such as
• Monarch butterfly larvae and the invasive plant Black swallow wort
• Aquatic invasive plants block sunlight from reaching submerged plants. Dead plant matter creates low oxygen conditions killing fish and other macroinvertebrates
• Invasive plants increase populations of undesirable pests:
  • Japanese barberry provides favorable tick habitat 
  • Deer prefer to browse native plants, creating openings for invasive plant growth 
  • Low oxygen conditions created by Eurasian Water Milfoil increases mosquito and fly populations

Human Communities

• Reduce flood mitigation and erosion control
• Increases in pests such as ticks, deer, mosquitos, black flies, and paper wasps weaken tree species and makes them susceptible to blowdown during heavy storm
• Other impacts: damage to physical infrastructure, reductions in recreational use, and degraded water quality 

What can I do about invasive plants growing on my property?

Removal
If you find invasive plants on your property, remove them as soon as possible. For private landowners, the Conservation Division encourages the use of hand pulling and mechanical removal. Applying pesticides safely and effectively requires training and experience. Using pesticides without understanding them can lead to toxic exposure and they may not kill the target plant. If you wish to treat invasive plants on your property with herbicides, please consult a professional vegetation management service.
Hand and mechanical removal are most effective when timed with the flowering, fruiting, growing, and dormancy periods of a plant's life cycle. Below is a management calendar for ten plants to help time removal efforts. 

To find out about the life cycle and best management practices for specific species, please visit Penn State Extension: https://extension.psu.edu/catalogsearch/result/?q=invasive+plants

Disposal
Safe disposal is an important part of effective management on private land. For herbaceous plants, solarization is an effective method of disposal. Place any herbaceous invasive plant in a black garbage bag and leave it in the sun to fully decompose. For woody plants, burning and chipping are the most effective methods of disposal. When possible, clean up all invasive plant berries and seeds. 

Identifying and managing invasives

Many good references exist in libraries, book stores, and on line to help with making accurate plant identifications.

In 2004, MIPAG completed a report offering recommendations for managing invasive plants in Massachusetts Strategic Recommendations for Managing Invasive Plants in Massachusetts. All state agencies within EEA are contributing in some way to this effort. It is important that management strategies be well researched and planned; otherwise scarce funds and human resources could be wasted. Information on the biology of invasive species and their management is increasing dramatically and much can be found on the web. New scientific journals have arisen that deal specifically with invasive species research.

• Identify and control or eradicate invasive plant species where possible, starting with one's own property or local conservation areas where control projects are underway or being planned. Volunteer with the Native Plant Trust to help with their invasive plant monitoring and control projects.
• Report any sightings to EDDMapS or to iNaturalist. Both of these on-line resources have phone apps as well, and both are checked by state employees concerned with invasive species. It is important to include numbers observed and area impacted in your report.
• Educate others and report anyone illegally selling, growing, or distributing invasive plants.
• Plant only native plant species or non-native species that have been researched and proven to be non-aggressive in terms of naturalizing into natural areas or minimally managed habitats in Massachusetts or New England.

Native Shrubs for Plantings as Wildlife Food 

Additional Resources

• Video: Managing Oriental Bittersweet
• Power Point: Managing Invasives on Your Property
• Massachusetts Invasive Plant Advisory Group
• Evaluation of Non-Native Plant Species for Invasiveness: Criteria Update 2022
• Massachusetts Priorities for Invasive Species Early Detection
• Guidance for the Effective Management of Invasive Plants
• Definitions Related to Invasive Plants
• NHESP's Invasive Plants in MA
• The Invasive Plant Problem (PDF 441.11 KB)
• Environmental Impacts and Economic Costs of Invasive Species (PDF 25.45 KB)
• Invasive Species Research (PDF 33.2 KB)
• Strategic Recommendations for Managing Invasive Plants in Massachusetts