The state has added 30 species to the list of plants that will be illegal to sell in Maine as of January 2024, joining the 33 plants that became illegal to sell more than three years ago. The plants are banned for sale because they are invasive, meaning they spread aggressively and crowd out native species.

Another 30 plants were added to a “species watch list.” The spread of this second group species will be monitored until, some five years from now, the Terrestrial Invasive Plant Stakeholder Committee begins considering anew which new plants to add to the banned list.

Under the new rules, rugosa rose, the fragrant beach rose that is prevalent throughout Maine but especially along the coast, gets its own category: “Invasive Terrestrial Plant of Special Concern.” More about that later.

All the new plants on the list arrived in the United States because some plant dealer at some point thought they would look nice in someone’s garden. A few plants in the original 33 arrived in America accidentally, as weeds growing in pots that were brought in for sale, for example.

State Horticulturist Gary Fish, who coordinates the committee, said that while local nurseries no longer sell many of the plants on the list, they are still available online. In the future, if all goes according to plan, Mainers will not be able to buy these plants online, either. While U.S online merchants, such as Amazon, have been working to adhere to Maine’s banned list, Fish said that it has been more difficult to enforce the ban with European plant sellers.

Let me start with what has been banned.

The Callery or ‘Bradford’ pear, an ornamental tree with abundant white blossoms, made the list, as expected. The ornamental tree was developed from a tree native to Asia and was originally thought to be sterile. Oops. It was spread by seed into the wild from domestic plantings in private gardens, public parks and along streets. Wild Callery pear tree stands now grow in southern Maine and more abundantly in states to our south. With warming temperatures, experts believe the tree will become more problematic in Maine.

Euonymous fortuneii, or wintercreeper, also native to Asia, has also escaped from people’s gardens into the wild, especially along rivers. A huge patch is growing underneath a bridge over the Kennebec in Augusta, Fish said. Several cultivars including ‘Emerald Gaiety,’ the one I have seen most often, are still sold in many nurseries, but gardeners shouldn’t shouldn’t be too worried about the coming ban, as it isn’t a plant that will cause a huge gap in anyone’s garden.

Fish said gardeners have long used creeping Charlie, which is native to the British Isles, as a ground cover. It too, is now on the banned list.

European alder has spread from gardens to Maine’s wild areas, as well, and is on the new list. Homeowners often intend to purchase native alders but get the wrong one by mistake, Fish said. With the ban, that won’t happen.

Such a lovely, fragrant rose. But even though you see rugosa rose everywhere along Maine’s coast, it is not a native. Now, the state has listed it as an “Invasive Terrestrial Plant Species of Special Concern.” It’s especially problematic near bodies of water. Pam Harnden/Livermore Falls Advertiser

Back to the rugosa rose, a native to Asia.

When the committee made its preliminary list late last year, rugosa rose was on the list of 63 plants under consideration to ban. I heard vigorous arguments, both online and in person, for and against the bush. People either love it or hate it.

So the committee settled on a compromise: While nurseries will still be allowed to sell rugosa roses, a label will be required – either on the container, in the soil, or in the area of the store where the roses are for sale. It must say “Invasive Terrestrial Plant Species of Special Concern.” The seller must also provide guidance to the buyer about inappropriate habitats for rugosa roses.

Rugosa roses, often referred to as “beach roses” because they grow there so abundantly, should not, in fact, be planted by the beach. Near water, rugosa roses are highly invasive; the rose hips – the red, Ping-Pong-ball-sized fruit that forms after flowering – can float a long way, perhaps miles from the original plant, and seed themselves. But planted inland, far from the ocean, lakes or streams, rugosa roses are not a serious problem, Fish explained.

The beach rose is special in another way, he continued. While the invasive species law bans any cultivar made with an invasive species as one of its parent plants, that won’t be the case with rosa rugosa. It is part of so many hybrids going such a long way back, such a rule would be impossible to enforce.

Many popular species that were on the initial list for potential ban have moved to the watch list. They include such popular plants as Japanese spirea (including “Magic Carpet” spirea, which is the one I see most often), Japanese tree lilac, hardy kiwi and Buddleia davidii, also known as butterfly bush. For now, these plants get a five-year reprieve.

Vinca (periwinkle), originally on the banned list, didn’t even make the watch list, but it probably will be discussed in five years, as well. Fish described vinca as a “colonizer.” It doesn’t spread long-distance through seeds, but rather by roots.

Tom Atwell is a freelance writer gardening in Cape Elizabeth. He can be contacted at: tomatwell@me.com.