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Got weeds? Read this before you whack them.

I was once a slayer of undesirables in my backyard, but now I understand the ecological benefits of non-native plant species.

The author's grandsons frolic among the native and non-native weeds in her Vermont meadow.Martha Leb Molnar

These days, I think about our Vermont meadow in spring as I once thought about my hair.

I came of age when long, straight, preferably blond hair parted in the middle was de rigueur for white girls. Mine was neither straight nor blond, and I spent unsuccessful years trying to tame it into what was supposedly right. Eventually, I settled for just straight bangs. In time, my hair and I reached a truce — albeit interspersed with regular flare-ups.

In a similar process, I was once a god striding our Vermont meadow, deciding which plants should live and which should die, based on whether they were right for a native meadow. I viewed every non-native plant, whether brought by wind, carried in pants cuffs, dropped by birds, or launched by spider silk as a foreign invader to be eradicated.


Getting rid of invasive weeds, even native ones, demands years of hard labor and focus. My husband and I were committed — until we met two archenemies: huge swaths of poison parsnip, which fought back with chemical burns on exposed skin; and Canada thistle, which seemed to colonize new ground overnight. Overwhelmed, I launched into frenzied research.

What I learned turned out to be confusing and troubling.

First, there is little consensus about what weeds are. Are all non-native plants weeds or just the ones that multiply rapidly? Are natives like goldenrod, which overwhelm other plants, also weeds?

Non-native plants are referred to as alien, foreign, illegal, exotic, menacing. Given that the references are based on the non-belonging, the foreignness of these plants, out of context it’s sometimes difficult to know whether the reference is to plants or people. As an immigrant, I find this disturbing.

I also learned that the Nazis were obsessed not only with the purity of the Master Race but also with the purity of their dark forests. The Reich Nature Conservation Act was designed “to cleanse the German landscape of unharmonious foreign substance.”


The truth is, most weeds have gotten a bad rap. There is new evidence that many non-native plants add to the success and diversity of an ecosystem, much as human immigrants add creative wealth to societies.

Puerto Rico is one example of rebounding biodiversity thanks, in part, to non-native plants. The island’s rainforests were denuded for agriculture, which was then abandoned in the middle of the last century. The empty land was a desert of drained wetlands and compacted soil. That’s when non-native plants — tulip and guava trees, rose apple and white iris, a prolific spreader that can cover 17 acres a year — moved in. They broke up and enriched the soil and provided a home for birds and insects, which spread the seeds of both native and non-native plants, creating new forests that were different from the original forests but functioning ecosystems. Similar phenomena have been observed in other places. There is a word — ecosynthesis —for these mixtures of native and non-native species.

Nor is there evidence that non-native species reduce the number of native ones. Only three of New Zealand’s native species have been lost while 2,000 non-natives have moved in. In California, out of approximately 6,000 species, more than a thousand are newcomers, yet fewer than 10 natives have become extinct.

Even ecosystems that brim with native species can absorb huge numbers of non-native ones, most of which live in harmony with the old timers. Many, from apples to lilacs and tulips, are well loved. My own state flower is red clover, native to Europe, Asia, and Africa but not to New England. Still, red clover, like many non-natives, is beneficial in many ways. It’s a nitrogen fixer, which makes it a natural fertilizer. It is beloved by bees for its nectar and pollen and by people for its medicinal properties.


Climate change is a boon to non-native plants, which may have no natural enemies in their new environment and flower and spread their seed earlier than native species. Unchecked, the thistle and parsnip in our meadow would prevail over the grasses and milkweed, turning the land into an impassable tangle useless to the ground-nesting bobolinks and Monarch butterflies.

Yet I see that the insects seem to like the non-natives and natives equally, while the returning bobolinks are content to nest among most tall plants. Even the invasive weeds — native or not — can be as beautiful as my cultivated flowers. The purple heads of thistle light up the drab grass of late summer. The multiflora rose, a newcomer I’m trying to ignore, flashes its snow-white blooms shamelessly. The dandelions are lovely until they become gangly teens.

One must admire weeds’ staying power. Chop off the head of a thistle, tear off its leaves, yank it out, dig it up. The tiniest sliver of root left in the ground will grow a whole new thistle.


All this new knowledge generated a radical change in my attitude toward non-native plants, underscored by a firm red line. On one side: poison parsnip and thistle. On the other: the immigrants that are not bent on conquering the entire meadow. I am learning to love them all, because, given the state of our planet, a thriving green landscape is a sight to cherish.

Martha Leb Molnar is an author and commentator who writes often about the natural world. Her most recent book is “Playing God in the Meadow: How I Learned to Admire My Weeds.”