Green Thumbs Up: Learn to recognize invasive intruders

Suzanne Mahler

Colorful carpets of creeping phlox (Phlox subulata), basket of gold (Aurinia saxatilis) and candytuft (Iberis) cascade over rock walls, walkways and landscape timbers creating glowing patches of pink, white, lavender and yellow. Pretty pansies in every color of the rainbow provide splashes of color in containers, window boxes and along garden paths, their smiling faces irresistible to young and old alike. Elegant tulips hold their heads high on strong, sturdy stems, reaching for the warmth of the sun.

As the month of April draws to a close, our landscapes have come to life as tender green leaves clothe trees and shrubs and spectacular blooms paint the landscape with multicolored artistry.

Despite minimal moisture in recent weeks, weeds and misplaced wildflowers are flourishing. Violets and dandelions are in bloom, making them easy to identify, but others are less familiar, especially early in the season. Many of these sprouts belong to plants now designated as invasive species, which include several popular favorites formerly available in the nursery trade and now banned from sale.

Invasive plants are non-native species that have spread into native or minimally managed plant systems. These plants cause economic or environmental harm by developing self-sustaining populations and becoming dominant and/or disruptive to those systems.

Wind, water, wildlife and humans disperse these invasive plants, which compete with and often crowd out our native species. This reduces biodiversity, which may then impact habitats for wildlife by reducing food and shelter as well as the host plants of beneficial insects. Some of these plants alter soil nutrients, acidity and structure, release toxins, or host diseases that can then spread to agricultural crops.

Many homeowners wonder why these plants are targeted, unaware of the invasive potential of these popular and commonly grown plants. Other gardeners have first-hand experience as these thugs have popped up all over their landscapes. Barberries, burning bushes, buckthorn, shrub honeysuckle, and multiflora roses were just a few of the plants that we found growing wild when we purchased our builder’s property more than 30 years ago. Attractive to birds and wildlife, I welcomed their colorful fruits at first, but soon realized their capacity to seed everywhere.

As invasive plants spread, it becomes increasingly important that homeowners learn to recognize and try to control the spread of these aggressive intruders. I regret my own inaction in earlier years that has allowed the reeds to overtake my meadow and massive vines of bittersweet to climb and strangle many of my native trees.

I have recently cut the thick, 1- to 2-inch stems of mature bittersweet vines to the ground and regularly pull the long, bright orange roots of spreading plants plus I now recognize tiny seedlings with their shiny round leaves, which also display orange roots.

Last year, several plants of garlic mustard appeared in a shady corner of my property. With rather attractive scalloped foliage and dainty white flowers, this cool season, biennial herb is currently in bloom. I tried to pull every plant of this tap-rooted weed last spring but despite my efforts, the plants have proliferated to form a broad carpet this year.

Learn to recognize invasive plant species on your own property. Start at and Your local nature center also should have information.

Small seedlings are usually easy to dig up and should be disposed of in your trash, not the compost pile. More persistent populations may require treatment with herbicides, assuming they are not within the confines of wetlands. Early action is essential as once some of these plants become well-established, eradication may become impossible.

Suzanne Mahler is an avid gardener, photographer and lecturer who has been developing the 1.5-acre property surrounding her home in Hanover, Mass., for more than 30 years. She is a member of two local garden clubs, past President of the New England Daylily Society, an overseer for the Massachusetts Horticultural Society and is employed at two garden centers.