Friday, March 7, 2014
By Tom Atwell
Invasive plants remain an issue in the gardening world, and they were a common topic among programs at the annual trade show of the Maine Landscape & Nursery Association last month in Augusta.
Autumn olive is already recognized as an invasive plant in Maine, along with Japanese knotweed and swallowwort.
Maine State Horticulturist Ann Gibbs reported that the state is about to hire a specialist in invasive plants. The position will be part of the Maine Natural Areas Program in the Department of Agriculture, Forestry and Conservation.
Gibbs said the state received 93 applications for the position, and that one of the new employee’s first duties will be to “develop a list of invasive plants” for Maine.
Maine now has a law banning the transportation of specific aquatic invasive plants, but it does not have a list of invasive land plants nor laws preventing their sale. Several other New England states do have such a list, and the University of Maine Cooperative Extension has a list of potentially invasive plants. Maine nurseries have stopped selling most of them,
The list includes Oriental bittersweet, Japanese barberry, Japanese knotweed, autumn olive, Oriental honeysuckle, burning bush, Norway maple and others.
Creation of a list of invasive plants probably will include debate on whether cultivars of some of these invasive species – which may or may not be invasive themselves – should be included on the list. It will be interesting to watch the process – and the result.
Rick Churchill, former chairman of the horticulture program at Southern Maine Community College and writer for the former People Places & Plants magazine, in another MELNA program discussed his firsthand experience battling invasive plants during creation of the first phase of the Arboretum at Fort Williams in Cape Elizabeth.
The site of the Cliffside Garden could have been a showcase for invasives, including knotweed, bittersweet, honeysuckle, Norway maple, swallowwort and more. He described how volunteers cut down and removed the invasive species. And when the plants resprouted, they cut them down again.
Once he had the invasive plants under control, he brought in native plants, including hayscented fern, that would keep the invasives out.
“People told me, ‘How can you plant that? It spreads everywhere,’ ” Churchill said. “Well, it does what we needed it to do” – cover the hill with ferns that were a bright green early in the season, changing to yellow and brown as the season progressed. Technically, because hayscented fern is a native plant, it can’t be labeled as invasive.
Other plants that he brought in were low-bush blueberries, bayberries and bearberries, all in sod form, although the blueberries brought a lot of weeds with them.
He reports some problems with the replanting. A white pine recommended by the landscape architect died the first year. Some pitch pines and jack pines that Churchill recommended looked dead, and he recommended that they be yanked. The architect recommended waiting, and the trees actually did produce more needles and looked OK later in the season.
A major problem was that there was just a little bit of horsetail equisetum in the soil that was brought into the site of the garden, and that is spreading rapidly. Horsetail is a weed that’s just about impossible to remove. So when you bring in soil, make sure it is horsetail-free.
Churchill’s talk was wide-ranging – the title was “What Plants Have Taught Me,” and he said he was added to the program at the last minute because the original program was all about marketing with no talks on plants.
One nugget on tree planting was new to me, and it made perfect sense. When Churchill first was in the business, guides said the hole for a plant should be 6 inches larger all around than the root ball. Now, he says, the guideline is to make the hole three times as wide as the root ball.
He recommends making the hole three times the size of the root ball, but to make a divot in the bottom of that hole the exact size of the root ball. That smaller hole will serve as an anchor for the tree, stiffer and more packed than the soil you put back. That anchor hole avoids the need for staking the tree.
For MELNA’s annual awards, Al Lappin Sr. of Al Lappin Landscaping in Scarborough won the Al Black Award as the state’s outstanding horticulturist for the year. Lappin began his career at Skillins Greenhouses in Falmouth before starting his own landscaping company, which also includes his sons. Lappin Sr. was credited at the meeting with giving early jobs to many of MELNA’s officers and other leaders.
Irene Brady Barber of Durham was named Young Nursery Professional of the Year. She is a horticulture therapist and landscape designer, working at Coastal Maine Botanical Gardens and her own company, Irene Brady Greenscape Designs. Earlier she worked at O’Donal’s Nursery in Gorham, where she formed the landscape design division.
Another interesting MELNA program was presented by Allison Dibble of the University of Maine, who discussed a trial on attracting native bees as pollinators. And bees love some great plants for pollinators, such as knotweed. Next week I will write about that program.
O’DONAL’S had not created its winter seminar program by the deadline for last week’s column. It will offer free programs on new hydrangeas with representatives from Bailey’s Nurseries and McHutchison Horticulture at 10 a.m. Feb. 20, insect and disease updates with two assistant state horticulturists at 10 a.m. Feb. 27 and new plants at 10 a.m. March 20. Call 839-4262 to register.
Tom Atwell has been writing the Maine Gardener column since 2004. He is a freelance writer gardening in Cape Elizabeth and can be contacted at (207) 767-2297 or at: