What are native plants? Simply put, they are plants that grow or grew in a particular place because they evolved there, in concert with other flora and fauna, to fill a particular niche in their ecosystem, and not due to human intervention. (By definition, “native” is a term that contains a relationship to place – a native displaced is no longer native, no longer at home.)
It is important to plant, sustain and encourage native plants because they provide food, shelter and other resources vital to other species and, consequently, to the ecosystem as a whole.
That’s the short version of my answer to the question of why I advocate for growing native plants in our gardens. For a slightly longer explanation, continue reading…
For the past three years, a group of us at the elementary school where I live have been teaching five to ten-year olds about plants and pollinators. You might say it’s a bit subversive: we show them monarch caterpillars munching away on milkweed leaves; later, we let them play with the tiny parachutes of milkweed fluff that the plant uses to disperse its seeds and teach them the connection: mother monarch needs milkweed; it’s the only place she can lay her eggs. Plant some milkweed in your garden or in a pot outside your door and she’ll come to you: she’ll lay her eggs on your milkweed plants and pretty soon caterpillars will hatch!
What child, introduced thus to the marvels of milkweed, wouldn’t want to plant some?
This is the best way to learn about native plants and the role they play in our ecosystems: hands-on and inches away from the creatures who depend on them. But since a lot of the information regarding native plants is only beginning to become well-known and many of us are coming to this knowledge later in life, it helps to turn to the experts.
For an introduction to the why of native plants, I refer you to two books in particular.
In Noah’s Garden: Restoring the Ecology of Our Own Back Yards, Sara Stein tells the story of the transformation of her garden, twice over. When she and her husband, Marty, bought a large piece of untamed property in Pound Ridge, they took it upon themselves to install gardens. Only, Stein got a bit muddled by the business at hand:
Of all the plants I planted in my unlettered days, few survive. Junipers succeeded, daylillies, some ferns. Asters fell from lack of staking and, undivided, soon dwindled away. Lillies rotted; phlox blackened; myrtle died of drought. Voles chewed the tulips while aphids sucked the lupines, and whatever lime or acid was needed by clematis and heather was not what they got, so they died too […] And everywhere everything was overcome by weeds (2).
I can relate.
Moreover, she was confused by “baffling divergences among the way of plants and the way of gardeners” as well as a fundamental difference between the ways in which horticulturalists and ecologists look at plants: “Gardners see aphids as enemies, moles as nuisances, and snakes as something the world would be well off without. Ecology sees all species connected in such a mesh of interdependence that one hardly dares step on an ant” (7).
With a background in science writing, Stein is perhaps more attuned to the words of ecologists than your average gardener. But what really shifts her perspective is the dawning realization that by clearing brush, digging up beds and planting new gardens, she and her husband inadvertently banished the creatures who lived there when she first arrived, the rabbits, the grouse, the grasshoppers, the fox and many others. She concludes that traditional American gardening is in a fundamental way wrong-headed. In the remainder of the book, she analyzes the ways America’s gardening tradition has wrought havoc with its ecology and proposes a new approach to gardening, using native plants to create and sustain habitat for wildlife.
And, finally, I must add, I have a particular affection for Sara Stein because she’s a good writer, a deep thinker and… she’s funny! I dare you to read the first chapter of Noah’s Garden, “Unbecoming a Gardener,” without laughing out loud.
More recently, we owe a growing awareness of the importance of native plants to a specialist in bugs, Doug Tallamy, Professor in the Department of Entomology and Wildlife Ecology at the University of Delaware.
In Bringing Nature Home: How You Can Sustain Wildlife with Native Plants, Tallamy opens with a story of his own garden: when he and his wife moved to a 10-acre property in southeastern Pennsylvania, they took it upon themselves to remove foreign, invasive plants and replace them with native species. (He had no doubt already gotten the memo from Stein and others that this was a good idea.)
As an entomologist, Tallamy noticed an interesting dichotomy:
The alien plants that were taking over the land – the multiflora roses, the autumn olives, the oriental bittersweets, the Japanese honeysuckles, the Bradford pears, the Norway maples, and the mile-a-minute weeds – all had very little or no leaf damage from insects, while the red maples, black and pin oaks, black cherries, black gums, black walnuts, and black willows had obviously supplied many insects with food (14-15).
Inspired by this simple observation, Tallamy has undertaken a series of research projects which have deepened our understanding of the food web in which native plants play an essential role. In talks he has given all around the country, he illustrates the importance of native plants in ways that help us non-scientists understand.
Observe a bird in your back yard, the fluffy chickadee, says Tallamy. We know that the adults will happily take seeds from our bird feeders all through the winter. But their young cannot process these hard foods: to grow, they need the soft, nutritious bodies of caterpillars. And, would you believe, it takes a pair of chickadees over 5,000 caterpillars to raise a clutch of hatchlings! And other birds – being larger – require even more!
But here’s the rub: caterpillars can’t hatch on any old plant. The children in our elementary school will tell you why: if they hatch on the wrong kind of leaf, they will likely be poisoned or simply die of starvation. This is because plants have developed a sophisticated arsenal of chemical protections over millions of years and it is on this scale of evolutionary time that caterpillars have adapted the ability to digest certain leaves. In other words, caterpillars are specialists.
In Tallamy’s appendix, he provides an extensive list of American butterflies and moths and the host plants on which they depend. Here are a few examples – note how lovely the names of our native butterflies:
American lady (Vanessa virginiensis; Host Plants: Composite family (Asteraceae), Pearly everlasting (Anaphalis margaritacea), Pussytoes (Antennaria dioica) Sweet everlasting (Granphalium obtusifolium)
Eastern Comma (Polygonia comma); Host Plants: Elm family (Ulmaceae), Hackberries (Celtis), Nettles (Uritica)
Great spangled fritillary (Speyeria cybele): Host Plants: Violets (Viola)
etc.
And of course
Monarch (Danaus plexippus); Host Plants: Milkweeds, butterfly weeds (Asclepias)
This particular model (host plants -> butterflies -> birds) does a good job of conveying the importance of native plants. But of course it only scratches the surface. Tallamy also tackles the issue from the other end of the spectrum: the importance of biodiversity in maintaining the health of an ecosystem.
No discussion of native plants – and their role in maintaining biodiversity – would be complete without addressing the problem of invasive, alien plants – exotic plants introduced into our nurseries and gardens whose seeds and stolons have escaped into the wild. The problem with these plants is that they are not functioning members of the ecosystem into which they are introduced – think of the leaves in Tallamy’s garden that remain intact because no one can derive sustenance from them. Moreover, removed from their home, they no longer face the kinds of controls on their growth and reproduction they experience in their home ecosystems; they grow out of control and displace native species.
Tallamy uses the example of the paperbark tea tree (Melaleuca quinquenervia) that has taken over huge swaths of the Florida Everglades. Its impact is devastating:
Melaleuca has transformed the sunny wet grasslands it has invaded into deeply shaded, drier forests dominated by a single species. The grassland birds that breed in the Everglades cannot nest in Melaleuca groves, and they find fewer insects to eat because native insects cannot eat Melaleuca leaves (Costello et al. 1995). Alligators cannot make their wallows or find food in Melaleuca groves, and so they have lost hundreds of thousands of acres of their habitat. Butterflies cannot find their host plants, egrets cannot hunt the fish they eat, and hummingbirds cannot find the nectar they need to survive from day to day (45).
And so on.
Closer to home, our New York forests – notably in Westchester where I live – are rampant with foreign species. Even before I knew much of anything about the local ecosystem, I sensed that something was wrong: the forest looked too much like a jungle. The vines I observed strangling and smothering the trees along the roadsides, creating an odd, dense look for a Northern forest, turned out to be oriental bittersweet, kudzu, mile-a-minute and other invasives. For those who are first learning about the role of native plants in our local ecosystems, it can be particularly unsettling to realize that our uncultivated areas, our parks and preserves, are often overrun with these foreign species, undermining our very ideas of what is “natural” and “wild.”
Thus, ironically perhaps, the burden falls back on the gardener. The bees, the moths, the butterflies, the birds and other creatures, increasingly, can no longer rely exclusively on nature to do her thing – so to speak. The poster child for this problem is the monarch, who has suffered from the systematic eradication of milkweed from our farmlands and its disappearance from our forest edges and other natural habitats. Some of us have gotten the message loud and clear: if we want monarchs, we have to plant milkweed. But, as Sara Stein understood, back in the 90s, the gardener has a role to play in maintaining much of our local wildlife.
Finally, I will return to Tallamy who addresses the larger question of why this all matters. If not for personal, moral or aesthetic reasons, why should we care? Why is the health of our ecosystems, which we know depends largely on their biodiversity, something we should fight for? To respond to this question, Tallamy introduces the issue of ecological sinks and sources and uses the example of New York City:
If New York City were an isolated entity without connections to other parts of the country, it would collapse – in less than a week. Manhattan island is an ecological sink; it requires the influx of great quantities of ecological resources that are generated in healthy ecosystems elsewhere (ecological sources) to sustain life. [….] People can live in New York City only because they take what they need to live from areas of the country that still have a healthy biosphere. The water that quenches the thirst of millions of New Yorkers comes entirely from an ecosystem that remains functional: the forest Catskill Mountains north of the city. The oxygen that New Yorkers breath is generated by the vast forests of the Amazon and by populations of phytoplankton in the sea. The fish that are served in exclusive West Side restaurants come from oceans all over the world. The beef comes from rangelands across the continent, and the grain from fragile topsoils laid down during the last glaciation in the Midwest. Every natural resource required to keep New Yorkers alive comes from ecosystems that have not yet collapsed (46-47).
As someone who had recently moved from New York City to the suburbs when I read this… well, it would be hard to understate the impact. I must, at some point, have lazily absorbed the argument that city dwelling is more environmentally sound – smaller carbon footprint, fewer cars, smaller apartments, more shared resources, etc. I felt morally uncomfortable about my move to the suburbs. But there I was, having Tallamy remind me that we can’t actually separate the environmental impact (or benefit) of one place from another. They are all of a piece. And there was my garden: the great paradigm shift of my move from the city to the suburbs. A garden and the question – what would I do? How would I contribute or detract from this wonderful breathing, living place we call earth?