Alien Invaders
by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station
It’s beautiful, it’s everywhere, and it’s an exotic invasive plant. Although not quite as big a handful as Audrey II from “Little Shop of Horrors,” this wetland beauty is every bit as dangerous to other plant communities. We are talking about purple loosestrife (Lythrum salicaria), which was introduced to the northeastern U.S. and Canada in the 1800s for ornamental and medicinal uses. Purple loosestrife is a perennial plant with tall purple flowers, a square, woody stem, and opposite leaves that grow best in wet soils. According to the U.S. Fish and Wildlife Service, purple loosestrife now occurs in every state except Florida. It’s one of the top exotic invasive plants on Nantucket. According to the Federal government, an "invasive species" is defined as a species that is 1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes, or is likely to cause, economic or environmental harm or harm to human health (Executive Order 13112). Invasive plants can be accidentally or deliberately introduced by means such as agriculture, as forage crops, as ornamentals or escapees from botanical gardens and estate gardens, through aquatic gardens, erosion control techniques, storms, or via hitchhiking pollen and seeds delivered by migrating birds. Human actions are the primary means of invasive species introductions. On Nantucket, the primary adverse effect perpetuated by invasive plants is ecological harm caused by habitat destruction as they out-compete other plants for nutrients, sunlight, water, and space. My article last week in Yesterday’s Island discussed the problem we are having with the Common Reed (Phragmites australis) taking over our marshes.
A subcommittee of the Nantucket Biodiversity Initiative (www.nantucketbiodiversityinitiative.org) called the Invasive Plant Species Committee (IPSC) is working hard to control the expansion of purple loosestrife and other exotic invasive plants on Nantucket while educating the public about their spread and effects on our island habitats. They have produced an excellent brochure entitled “Space Invaders: Weeds Gone Wild on Nantucket” that lists the top 10 highly invasive plant species of Nantucket and documents primary control methods and non invasive alternative plantings (see table below). Some of these plants are also listed on the Massachusetts Invasive Plants Advisory Group’s website (www.massnrc.org/MIPAG) and some are uniquely destructive on Nantucket. Fortunately, there are some very serious terrestrial and aquatic invasive plants causing havoc on the mainland that have not reached our island. Members of the IPSC include members representing the many conservation and research groups in the NBI and representatives from the Nantucket Garden Club and the Landscapers Association along with area surveyors and interested parties.
One of the most visible recent efforts of the IPSC can be seen as you walk along Pleasant Street between Office Products and Nantucket Bank. With generous contributions from the abutting businesses such as Nantucket Bank, the Marine Home Center, and the Commons Association, the IPSC has launched an attack on that lot on the insidious invasive plant, Japanese Knotweed, (Polygonum cuspidatum). Close to three years of work is starting to make a dent on the 15-foot-tall plants that littered that area. The eradication effort was almost stymied by the extensive amount of rubble spread throughout the lot due to its former function as a dumping area. Japanese knotweed is one of the most difficult plants to control and it has emerged throughout the island as it is transferred in fill and through construction projects. Soil containing even a small piece of knotweed larger than a ¼” in diameter can harbor a vegetative nightmare. Currently the IPSC is also investigating the best methods to eradicate this pest and limit its distribution. Evolution in action can be seen in Coffin Park, off Cliff Road, as Japanese Knotweed has hybridized with Giant Knotweed, another highly invasive plant, to create a new and perhaps more successful invasive plant as documented by UMass Boston Biology student, Melinda Gammon. Other IPSC projects over the past three years include a garlic mustard (Alliaria petiolata) pull near the Old Mill and three years of mechanical and chemical control on purple loosestrife along Sesachacha Pond with volunteers and invasive plant specialists. In addition, The Nantucket Conservation Foundation, the Nantucket Land Bank Commission and the Nantucket Branch of the Massachusetts Audubon Society have several permitted projects underway to eradicate various invasive plant species. A Conservation Commission permit is required for these projects and frequent monitoring to evaluate the success of removal efforts is included as part of the process.
An excellent reference featuring color images of each plant intruder is “A Guide to Invasive Plants in Massachusetts,” which is produced by a partnership between the New England Wild Flower Society, The Nature Conservancy, the Natural Heritage and Endangered Species Program, and the Massachusetts Division of Fisheries and Wildlife. Copies are $5 each and can be ordered by downloading a form from www.mass.gov/dfwele/dfw/nhesp/publications/nhesp_pubs.htm. I was surprised that the scourge of the southeastern states, kudzu (Japanese Arrowroot) has managed to infiltrate some areas around Boston! Another excellent resource for invasive plants on Nantucket is the Electronic Field Guide to Invasive Plants of Nantucket at efg.cs.umb.edu/nantucket. On the site you’ll find a list of invasive plants common on Nantucket with both the common and scientific names and a separate page with pictures and facts about each plant. This project is a collaborative work between the University of Massachusetts Boston, the Maria Mitchell Association and other members of the Nantucket Biodiversity Initiative (NBI). Another online reference with many useful links is Dr. Jennifer Forman-Orth’s site located at www.knottybits.com.
Every few years, the Nantucket Conservation Commission reviews their regulations and makes changes or additions or deletions after conducting a series of hearings. The most recent regulation changes included an update of the plants considered to be exotic invasives and potentially hazardous to wildlife habitat and functions in accordance with the recommendations and lists developed by the IPCS. Protocols developed by the IPSC on minimizing the spread of these plants and proper removal and storage techniques has also been developed to assist the Conservation Commission and Town of Nantucket agencies such as the Department of Public Works. The most recent research by the IPSC is concentrating on testing seed viability following composting for some of our most menacing plant invaders.
Curious to see these habitat assassins at work? Be sure to join us for a free guided walk sponsored by the IPSC on Saturday August 16 at 10 am at Lily Pond to learn all about these green invaders. Several members of the IPSC will be on hand to show the public different examples of invasive plants lying in wait in the peaceful confines of Lily Pond and adjacent properties. We’ll meet at the parking lot off the intersection of North Liberty St. and Grove Lane. Lily Pond is a short walk from town and can be reached by walking down Centre Street from Main turn left onto either India Street or Hussey Street and then turn right at Gardner. Gardner splits into Lily (on right) and North Liberty (on left). This event is sponsored by the NBI partners which include the Linda Loring Nature Foundation, Maria Mitchell Association, Massachusetts Audubon Society, Nantucket Conservation Foundation, Nantucket Garden Club, Nantucket Islands Land Bank Commission, Nantucket Land Council, Natural Heritage & Endangered Species Program of Massachusetts Division of Fisheries & Wildlife, Science Department of Nantucket High School, The Trustees of Reservations, Tuckernuck Land Trust, and the University of Massachusetts Boston Nantucket Field Station.
Highly Invasive Species
Non-native species that have spread into native or minimally managed plant systems on Nantucket. These plants cause economic or environmental harm by developing self-sustaining populations and becoming dominant and/or disruptive to those systems; and/or small populations of plants that exhibit highly invasive characteristics on Nantucket.
- Celastrus orbiculatus - Oriental Bittersweet
- Centaurea maculosa - Spotted Knapweed
- Elaeagnus umbellata - Autumn Olive
- Lonicera japonica - Japanese Honeysuckle
- Lythrum salicaria - Purple Loosestrife
- Phragmites australis - Giant Reed
- Pinus thunbergiana - Japanese Black Pine
- Polygonum cuspidatum - Japanese Knotweed
- Rosa multiflora - Multiflora Rose
- Vincetoxicum nigrum - Black Swallow-wort
Likely Invasive Species
Non-native species that are mostly restricted to disturbed or landscaped areas, but are considered a moderate threat to natural areas and may become highly invasive with time.
- Ampelopsis brevipedunculata - Porcelainberry
- Euphorbia cyparissias - Cypress Spurge
- Holcus lanatus - Velvet Grass
- Lonicera morrowii - Morrow’s Honeysuckle
- Rosa rugosa - Saltspray Rose
Potentially Invasive Species
Non-native species that are highly restricted to disturbed or landscaped areas and appear not to be threatening natural communities at this time.
- Cytisus scoparius - Scotch Broom
- Epilobium hirsutum - Hairy Willow-herb
- Erodium cicutarium - Stork's Bill
- Glechoma hederacea - Gill-over-the-ground
- Ligustrum vulgare - Privet
- Ranunculus repens - Creeping Buttercup
- Solanum dulcamara - Bittersweet Nightshade
Species highly invasive elsewhere that occur on Nantucket
Non-native species with either few occurrences or low numbers on Nantucket and that appear to be stable in terms of population size but are considered to be highly invasive elsewhere in Massachusetts.
- Alliaria petiolata - Garlic Mustard
- Acer platanoides - Norway Maple
- Acer pseudoplatanus - Sycamore Maple
- Aegopodium podagraria - Goutweed
- Ailanthus altissima - Tree-of-heaven
- Berberis thunbergii - Japanese Barberry
- Euonymus alatus - Burning Bush
- Glaucium flavum - Horned Poppy
- Hesperis matronalis - Dame's Rocket
- Iris pseudacorus - Yellow Flag
- Robinia pseudoacacia - Black Locust
Indeterminate species
Non-native plants that appear to pose a minimal threat or those for which we have insufficient data to make a determination about their status. When additional information becomes available, these plants will be revisited to determine their true status.
- Chrysanthemum leucanthemum - Oxeye Daisy
- Cichorium intybus - Chicory
- Elaegnus angustifolium - Russian olive
- Hedra helix - English Ivy
- Hypochaeris radicata - Cat's Ear
- Lespedeza cuneata - Sericea Bush-clover
- Linaria vulgaris - Butter-and-eggs
- Myosotis scorpioides - True Forget-me-not
- Phlox paniculata - Garden Phlox
- Plantago lanceolata - English Plantain
- Populus alba - White Poplar
- Tussilago farfara - Colt's-foot
- Verbascum thapsus - Common Mullein
- Vinca minor - Periwinkle
Resources used by the IPSC to develop the list above:
The evaluation of non-native plant species for invasiveness in Massachusetts. Massachusetts Invasive Plant Advisory Group, February 28, 2005, and Sorie, B.A. and P.W. Dunwiddie. 1996. The Vascular and Non-vascular Flora of Nantucket, Tuckernuck, and Muskeget Islands. MAS, MNHESP, MMA, TNC. Nantucket, MA.
