Last Spring, I went out to visit a large local "native prairie" planting around town and found landscapers there getting ready to till a large part of the garden. Just a few years eariler, this plot of land had been prepared for this native planting with a thorough regimen of multiple tillings and sprayings of herbicides to eliminate exotic weed pressures. Unfortunately, as is often the case, it wasn't enough. A few non-natives still managed to survive and take hold. While the natives were slow to establish, these speedy weeds took over. Now, MAN had to re-exert his influence by beating back the "invaders."
For those of us who love native plants and have tried to create "native gardens," this is a familar story.
In fact, complaining about "invasive weeds" is probably the favorite pass time of native gardeners, and it's certainly the #1 question I hear from environmentally-minded landscapers. We weed, water, and pamper them non-stop, but our native plants just don't seem to do their part. It has become commonplace for native plant landscapers to use more tilling, chemical intervensions, and other non-natural techniques in native gardens than even the most intensive vegetable gardening operations. Even in their native environment, our "native plants" seem frail and poorly adapted to survive in competition with weeds that evolved in very different conditions in Eurasia and elsewhere.
No wonder we "nature lovers" turn into raging nature-cidal maniacs at the sight of "invasive plants." It seems impossible to keep these brutes from man-handling (plant-handling?) our beloved home-team heroes.
So, what "in earth" is going on here? We hear all the time that our native plants should be "care free" and "adapted" to our growing conditions, so why do these exotic "weeds" so easily kick the good guys' butts?
Here's the shocking answer: We may have "native plants," but we're not planting them in the "native conditions" they evolved to thrive in.
Here are three ways we do our natives wrong, including the #1 most shocking reason that blew my mind when I learned about it.
Problem 1: Non-Native Plant Communities.
For most of us home owners gardening on the small scale, our goal is simply to convert some of our flower gardens into habitat for native plants. This especially seems like a good idea since they're supposed to require less maintenance than the exotics we're used to. But, it turns out that "native flower gardens," filled with species (selected for their beauty to human observers) just aren't a naturally occurring ecosystem. Anywhere. Ever.
For example, in the Great Lakes region, like most of the Eastern Woodland East of the Mississippi, there weren't even any large, stable areas of "native prairie," the kind of ecosystem most imitated by Michigan's native plant gardeners.
See that? No large swaths of "native flower gardens." The dominant ecologies of "pre-settlement" Michigan were almost entirely treed landscapes, with small bits of temporary prairie.
Now, don't get me wrong! I LOVE the "native prairie" gardens that are lovingly maintained around the city. They're beautiful, artistic assemblages of native plants that aren't easy to find or see growing naturally in the wild. But, where prairie systems occurred in the Great Lakes region, they were ephemeral, "disturbance ecologies" resulting from forest fires, storms or other openings in the forest ecologies. Which means, they were never meant to last.
That "native prairie" planting I started the article with? It's trying its darndest to become a REAL native ecology: a forest. And the only thing that will ever stop it is more tilling, weeding, spraying, burning or other human intervention.
Problem 2: You Are Your Native Garden (Except, You Don't Know It.)
When the first European settlers moved through the Eastern Woodland Region they described a startling landscape filled with a profusion of native wild flowers. It was common for these ecosystems to be compared to the most lovely flower gardens of old Europe.
So, maybe "native flower garden" really was a naturally occurring ecosystem of pre-settlement North America, after all?
Well, within a single decade of settlement observers began to note the complete disappearance of these wildflower ecosystems, replaced by a mosaic of tended grasslands, farms, and dense jungle thickets. That's all it took, 10-15 years, and they were gone.
Even then, it was clear to many period writers and naturalists what had happened: we removed the "native gardeners" who used to tend these native flower gardens. For the most part, it was the interactions of native peoples that maintained these "anthropogenic" (man-made) systems by the wide-spread practice of burning. As a horticultural practice, this was an extremely low-energy way of maintaining the high food-quality of large parcels of land.
What it means is that those "native flower gardens" and "native prairie gardens" have always depended on human intervention (at least since the mass extinction of North American Megafauna, but that's a story for another time....) Humans have always been the "keystone species" of these ecosystems, meaning we two-legged critters are fundamentally responsible for shaping and maintaining them. Since it's now impossible for us to carry out large-scale burning to maintain these gardens with low-energy systems, we must necessarily use more environmentally destructive, more energy-intensive means such as mowing, hand-weeding, tilling, spraying poisons and managed burns - if we're indeed dead set on maintaining these "pure" native plantings.
But, even this is harder to do these days then in pre-settlement times, because of....
THE #1 MOST SHOCKING REASON FOR WEEDS IN NATIVE GARDENS:
Problem 3: Our Soil Isn't Native Anymore.
Exotic plants aren't the only "invasives" in our native gardens. We also have to deal with exotic soil ecologies and the exotic soil organisms that make them up, for example, in the Great Lakes region, earth worms.
That's right, in the Great Lakes region, north of Ohio, Indiana, and Pennsylvania, ALL earth worms are an "invasive species."
All earthworm species in our region were driven out by glaciation in the last ice age, just as St. Patrick drove the snakes out of Ireland. Well, except for they were worms instead of snakes. And St. Patrick was massive sheet of ice.
If you're having trouble believing this, you're not alone. I've had folks with advanced degrees in life sciences argue fiercely that this couldn't possibly be true, and that earth worms were GOOD for plants, which means they must be good for native plant gardens, too.
So, before we go any further:
The Wikipedia article on Earthworms as an Invasive Species:
From the Smithonian:
And a quick Google Search will reveal many organizations dedicated specifically to stopping the spread of these invasive species that we so gleefully invite into our gardens.
By the way, if you guessed that the picture at the top of this article was earth worm cocoons, then you guessed right. Gold star for you.
You see, this "invader" status is exactly what makes worms so useful in our vegetable gardens: we're trying to grow vegetable plants that evolved in ecologies with earth worms and the diverse bacterial soil community worms encourage.
Earth worms don't just live in the soil, they make it. They are the primary soil architects in their ecosystems. Another "keystone species." They fundamentally change the soil ecology, enriching it with a great diversity of non-native bacteria from their gut flora. Where you have worms, bacteria dominate the soil microflora, instead of the fungi that dominate non-wormy native soils.
These wormy soils rapidly convert decaying matter into a nitrogen-rich super-food for our vegetables (and weeds.) But our native plants evolved in soils without worms. Without worms, the soil surface builds up a thick "fungal duff" that lasts for a much longer time, freeing up nitrogen at a slower rate and releasing it in different forms. So, our native plant communities evolved to be able to compete well in this slower environment, steadily converting that slow nitrogen release into long-term perennial growth.
This means that natives, with their slower metabolisms, just can't metabolize that "junk food," so they can't compete with "weeds" that evolved to turn that super-fuel into rapid growth. It's a "tortoise vs. hare" thing, but in wormy soils, the odds are stacked against the "native" tortoise.
The Moral to the Story:
"What's it all mean?"
Simply put, we have so many problems with "invasive weeds" because we're trying to grow "native" plants in non-native plant communities, in non-native ecologies, without their most important keystone species (native Americans) on non-native soils dominated by non-native soil life. The natives just didn't evolve for that challenge.
Well, what on earth do we do about this?!"
Hey, I'm not the boss of you. If you love your garden of pure native flowers, fantastic! Keep on keepin' on! If I happen to pass by it, you'll make my day, and if I get a chance I'll thank you for it!
But if you're stressed out about "invasive weeds" there isn't a thing I can give you - not even a well-functioning time machine - that can eliminate weeding and maintenance problems in these non-native "native gardens." That's just part of the deal, and it always has been, even before the "invasive weeds" came along.
On the other hand, if you'd like to put this new ecological knowledge to work for you, to make your environmentally friendly "native garden" even more beneficial while simultaneously reducing your maintenance work, here are four great Permaculture tips for making your native garden even better:
1. Try to Plant in Native Ecologies. Remember that map up yonder? In the Great Lakes region, that means that your young disturbance ecology wants to become some kind of forest. This is called "natural succession." You've got two choices. Either, you can go to eternal war with the process of natural succession to keep this natural process from happening, or you can let it happen, work with it and gently guide it along. Plant complete ecosystems including woody perennials and appropriately sized trees.
2. Fight worms with "natural succession." So, those invasive earth worms that are tag-teaming with the invasive plants? There's only one way we know of to fight them back, and luckily, it doesn't take a bunch of poisons from Monsanto or a bunch of imported oil from the Middle East. It's the energy of forests. Soils dominated by woody perennial plants and the acidic "tannins" in their tissues are resistant to earth worms. So, if you plant complete ecosystems that mature into forest, over time, you can actually transform non-native, wormy soils into the native forest soils with a deep fungal duff that your native plants can finally thrive in! Once it gets to this point, it will be the exotics that get their butts kicked around the garden.
3. Be patient, don't be a purist. But until that time that your native ecology can transform your soils, there will be weeds. So, be patient and accept it. It's probably more environmentally friendly to tolerate the presence of a few "invaders" than to waste energy, cause carbon pollution and spray poisons to "EXTERMINATE!" them. In fact, tilling, spraying, and disturbing the soil all destroy the growing soil diversity that will help soils move towards being more like native forest soils, so not only are you wasting resources to fight nature, you're actually fighting against yourself.
Better yet, why not work with those "invaders?" Many observers have noted long-term stable ecologies that include rare or endangered native plants along side "invasive" species. Permaculturists like Toby Hemenway call these "recombinant ecologies." So, if you keep endlessly weeding out the same species again and again, why not see if it can naturalize with your natives? Alone, your non-native plant community of native flowers will never be able to form a stable, self-regulating community on non-native soils. But with the inclusion of a few well-chosen "invaders" it's possible that your garden can "click" and form an ecology that will be more stable and easy to maintain.
4. Have your natives and eat them, too. If native flowers evolved in ecologies maintained by human agricultural activities, why not try to truly recreate this native ecosystem type by eating out of your garden? Your plants need your intervention as a "keystone species," so why not reclaim your proper place in nature as a beneficial member of the ecosystem? And if your native garden requires energy input anyway, why not use that energy input to reduce your overall energy and environmental footprint by growing some of your own food? There are many native plants that make excellent fruits and vegetables. Not only are the delicious, but these "wild" plants are usually especially nutritious.
Best of all, these native fruits and vegetables can be grown in a stable, low-maintenance and beautiful "food forest garden."
My friend PJ Chmiel and I have put together a list of some of our favorite "native" edibles to start with. You can get it for free by signing up for my free miniseries on creating Food Forest Gardens.