Invasive Plants
More Invasive Plants coming to Carol J. Smith, GCFM Native & Invasive Plant Chairman You may have seen articles in our local papers that the State of Maine has confirmed several sightings of Giant Hogweed (heracleum mantegazzianum) in our state. State Horticulturist Ann Gibbs was quoted as describing this plant as, “Queen Anne’s Lace on steroids.” Giant Hogweed is a noxious, invasive, herbaceous perennial plant in the parsley family (Apiaceae) that can grow to heights of 15 feet or more! It was first brought into the The leaves of giant hogweed are deeply lobed and incised and can be as large as 9 feet wide. The stem is green with dark purple blotches, ridged, hollow, and covered with coarse white hairs and raised nodules. The white flowers appear from late spring through mid summer and grow in flat topped umbels. And - it is one large plant! Giant Hogweed Sightings of this plant have been made in more than 30 areas in Maine; in Windham, Sebago, Northport and Lisbon Falls. Giant Hogweed is native to the Caucasus Mountains in Russia and Asia. Like most invasive plants, it was introduced as an ornamental. Giant hogweed is often confused with other members of the parsley family such as cow parsnip (Heracleum maximum), poison hemlock (Conium maculatum) and wild parsnip (Pastinaca sativa). The Invasive Plant Atlas of New England has a guide that helps gardeners distinguish between these plants. Some of theses features are that the purplish blotches are more raised and bumpy, and the hairs on the under surface of the leaf are shorter. Cow parsnip seeds also tend to be wider at the base whereas giant hogweed seeds are more often elliptical, the same width at the base and seed tip. Close up photo of Giant Hogweed’s flower: Leaves of the Giant Hogweed can be 2 feet long: Spreading by seed, Giant Hogweed has escaped into numerous areas in the northeast. It can crowd out other plants and take over natural areas, especially in moist areas such as stream banks. Somewhat shade tolerant, Giant Hogweed can also thrive in full sun and has been known to invade healthy turf. If you think you have seen this plant in your area, please call or email me so that we can get someone to absolutely identify the plant as Giant Hogweed. Then steps can be taken to eradicate it. The best way to prevent the spread of this plant is to cut the flower heads off in late summer, before they have a chance to go to seed. In early spring, cut the plant off at the root, or use herbicides. Always wear gloves and long sleeves when handling this plant. Photos used in this segment are courtesy of Plant Atlas of New England (IPANE)
Invasive Plants
Most invasive plants are not native to
This series describes invasive exotic plants that present threats to native
Some of the potentially invasive terrestrial plants in
- Purple loosestrife (Lythrum salicaria)
- Japanese barberry (Berberis thunbergii)
- Oriental bittersweet (Celastrus orbiculatus)
- Japanese knotweed (Fallopia japonica)
- Smooth and common buckthorn (Frangula alnus and Rhamnus cathartica)
- Non-native honeysuckles (Lonicera spp.)
- Garlic mustard (Alliaria petiolata)
- Multiflora rose (
- Small-flowered tickle-grass (Deschampsia cespitosa ssp. parviflora)
- Common reed (Phragmites australis)
- Asiatic Bittersweet Celastrus orbiculatus)
- Autumn Olive (Elaeagnus umbellate)
- Norway maple (acer platanoides)
One potentially invasive plant that surprise people is in the maple family. The Norway Maple (acer platanoides) are similar in habit to our native maples.
Norway Maple (acer platanoides) habit
Norway Maple (acer platanoides) - flowers with new leaves
The difference in the species can be seen in the fruit.
Fruit of Norway maple
Fruit of sugar maple
The seeds are contained in these winged samaras and are dispersed by wind. New trees grow quickly, shade out native understory vegetation and out-compete native tree species in the forest canopy.
Other similarities are in the leaf colors.
Norway Maple (acer platanoides) fall foliage
Like our sugar maples (Acer saccharum), It is difficult to educate gardeners about Asiatic Bittersweet (Celastrus orbiculatus). It grows abundantly on roadsides in
Asiatic Bittersweet (Celastrus orbiculatus) fruit
Asiatic Bittersweet is a perennial, deciduous vine that grows up to 60 feet causing major damage to native plants by girdling and mechanical damage to trees because of the additional weight added onto the branches, causing the branches to break. It’s vigorous growth shades other species and there is the possibility of it displacing American bittersweet (Celastrus scandens). The main feature that differentiates between the two plants is the location of the inflorescence, or cluster of flowers. The native American bittersweet inflorescence are located terminally, at the tip of the stem: If you have any questions or comments, please email or call me. Next month, we will feature one or two more invasive plants that you should consider avoiding. Carol J. Smith, GCFM Chairman Native Plants/Endangered Species/Invasive Plants Information and photo credits: Recommended reading:
Here is a photo of the non-invasive Native American bittersweet (Celastrus scandens) fruit, that is very similar to the invasive celastrus orbiculatus fruit:
Close-up of staminate flowers of invasive species
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