Navigating native and non-native plants
For many of us, gardening is a joyful hobby that brings peace and relaxation — a welcome distraction from the outside world. Few things provide the instant satisfaction of planting a tree or weeding and mulching a garden bed. But even the simple act of weeding or choosing the right tree for your garden can be a challenge when trying to navigate the nuances of the native, nonnative, and invasive plant landscape.
Decisions about what plants may be suitable, desirable, or ecologically beneficial can be tough. A variety of factors complicate our choices. Worcester, for example, has been under an Asian Longhorned Beetle eradication and quarantine effort run by the USDA since 2011. It’s still not advisable to plant some native tree species that host beetle larvae to prevent potential spread of this invasive insect beyond the quarantine zone.
Many plants, like burning bush (Euonymus alatus), once considered fantastic garden introductions from other parts of the world, are now considered invasive and prohibited for sale or distribution in the Commonwealth. Meanwhile, plants like English ivy (Hedera helix) and hardy kiwi (Actinidia arguta) are potential threats to minimally managed areas and under watch for consideration as invasive species. Though not banned now, they could be in the future.
According to the Massachusetts Invasive Plant Advisory Group (MIPAG), invasive plant species are “non-native species that have spread into native or minimally managed plant systems in Massachusetts. These plants cause economic or environmental harm by developing self-sustaining populations and becoming dominant and/or disruptive to those systems.”
MIPAG is a collaborative of members that represent research institutions, nonprofit organizations, the commercial green industry, and state and federal agencies. They meet regularly to review data and make recommendations to the Massachusetts Department of Agricultural Resources (MDAR) about whether plants should be added to the state’s prohibited plant list. MIPAG’s website also offers lists of plants that have been reviewed but do not currently meet the strict criteria for admission on the list of plants to avoid.
Few plants truly rise to the level of “invasive” as defined above, escaping cultivation and threatening biological diversity in natural areas. According to the Native Plant Trust’s 2015 State of the Plants report, more than 3,500 different plant taxa have been documented throughout New England.
Roughly 30% of those plants were introduced from other parts of the world and fewer than 200 of those introduced plants are considered invasive, posing a threat to natural areas. This is the true mark of an invasive species: a plant that impacts natural areas or poses an economic threat, perhaps to agriculture or another industry. For those plants that do pose an ecological or economic threat, state and federal agencies regulate their sale and distribution.
Experienced gardeners know well that some plants, whether native or invasive, grow beyond the boundaries we set for them in our gardens. Japanese spurge (Pachysandra terminalis), a dense, mat-forming evergreen groundcover, comes to mind. While it’s an effective groundcover, many gardeners regret planting it after realizing how quickly it can spread.
We personify these plants, describing their behavior as “aggressive,” or we call them “garden thugs.” Although we may regret planting them, and we might vilify them for being successful, plants are not sentient beings. They don’t “behave.” They simply grow in response to their environment, and some plants are more successful than others at adapting to a new environment when introduced from other parts of the world.
We often add our own sense of morals into the equation when deciding what’s “best” or “right” to plant. Instead, let’s do what we can with what we know. Before considering whether to add a new plant to your garden, consult the state’s invasive plant list, or another trusted resource. And to be sure you’re not introducing an invasive plant to your garden, consider planting something that’s native to the region. Native plants are locally adapted, support local birds and other wildlife, and can be wonderful ornamental plants for your garden.
Gardening Central Mass. is written by New England Botanic Garden at Tower Hill CEO Grace Elton and Director of Horticulture Mark Richardson. Located on 171 acres in Boylston. New England Botanic Garden creates experiences with plants that inspire people and improve the world. Learn more at www.nebg.org . The column is published on the third Sunday of the month.