If you've ever had mint take over a raised bed or watched bittersweet swallow a tree, you've probably used the word "invasive." But that word means something very specific to your state's Department of Agriculture — and it may not mean what you think.

Two Definitions of Invasive

When an agricultural agency classifies a plant as invasive, they're making a regulatory determination. In New England, plants on the prohibited invasive species list are illegal to collect, transport, sell, or propagate. These are plants that have escaped cultivation, spread without human help, and are actively displacing native species at a landscape scale.

For a gardener, invasive usually means something simpler: this plant is spreading where I didn't ask it to. It's crowding out what I planted. It's hard to control. Sometimes those two definitions overlap completely. Sometimes they don't overlap at all.

Officially Invasive Plants in New England

These plants are on the prohibited list for good reason:

  • Multiflora Rose — Introduced for erosion control and livestock fencing, it produces up to 500,000 seeds per plant per year and forms dense thickets that eliminate native understory plants.
  • Oriental Bittersweet — A climbing vine that girdles trees, topples them with canopy weight, and spreads via bird-dispersed berries. The roots are distinctively orange.
  • Japanese Knotweed — Hollow bamboo-like stems, heart-shaped leaves, root systems that go 10 feet deep and 60 feet laterally. It breaks through pavement and foundations.
  • Japanese Barberry — Linked to increased deer tick populations. Dense low growth creates ideal humid habitat for ticks.
  • Purple Loosestrife — A wetland invader producing up to 2 million seeds per year. Still sold as an ornamental in some places despite being prohibited.
  • Burning Bush — Popular for fall color, but birds spread it into natural areas. Replace it with highbush blueberry or native viburnums for similar effect without the impact.

Garden-Aggressive But Not Prohibited

Some plants will run roughshod through your garden without appearing on any official list.

Mint spreads by underground runners called rhizomes and will cross beds, find its way under edging, and colonize a large area in just a few seasons. The solution is containment from the start — plant it in a container, or sink the container into the ground with the rim above soil level to stop the runners.

Wild raspberry and blackberry are native plants with real ecological value. Birds, small mammals, bears, and native pollinators all depend on them. But along a garden edge, their tip-rooting canes and thorny thickets can move into your beds fast. Management here isn't eradication — it's consistent cutting and keeping them where you want them.

Poison ivy is also native, ecologically valuable, and not on any invasive species list. The problem is entirely the human response to urushiol. Protective gear is non-negotiable for removal — long sleeves, gloves, eye protection — and because birds keep reseeding it, management is ongoing.

Know What You're Managing

The approach to removing multiflora rose is different from managing wild raspberry along a fence line. One is a prohibited species doing ecological damage. The other is a native plant that belongs here — it just needs to stay in its lane.

Know your plants, know why they're there, and manage them accordingly. When in doubt, your local cooperative extension office can help with identification and removal guidance specific to your region.