The flowers you plant can harm — or help — our ecosystem

By Pamela White

How much environmental harm does your flower garden cause? Forget for a moment the water you have to pour on it all summer long to keep those beautiful blossoms alive. Forget chemical fertilizers, fungicides and insecticides. Forget its carbon footprint — the carbon emissions caused by your trips to the garden supply store, the miles the seedlings traveled before reaching your flowerbed, the energy that went into planting and sprouting them.

Think instead of the environmental havoc your flowers and bedding plants create just by surviving and thriving.

If you plant non-native species in your flowerbeds, you might be unwittingly contributing to the destruction of native flora on our open space and mountain parks lands. And that, in turn, harms the insects and animals that call our foothills and prairies home.

“How can that be?” you ask.

The answer is blowing in the wind. And landing with a plop in bird or animal droppings. Or riding on the bottom of your shoe. Or heading down the trail stuck to your dog’s coat.

“Any of those sorts of methods could allow a seed from some nasty thing in your garden to travel way up into the mountains,” says Dave Sutherland, an interpretive naturalist with City of Boulder Open Space and Mountain Parks. “If the wind blows a particular kind of seed up into the mountains, then it can start to grow up on Open Space and Mountain Parks land or on Forest Service lands.”

In fact, the invasion of non-native plants is one of the biggest ecological problems land managers face these days.

“It’s very serious,” Sutherland says. “Most people don’t see it. I go for a walk, and I know which plants are the non-native plants. They’re everywhere. They’re all along the trail. Chautauqua Meadow is almost a sea of non-native plants any more. Most people don’t have a botanical background. To them they’re just plants, and they don’t see what has really happened.”

Among the worst offenders are Dalmatian toadflax and myrtle spurge, also called donkey tail spurge.

“Dalmatian toadflax … is not just on OSMP land, it’s all over Yellowstone,” Sutherland says. “The sap in myrtle spurge is just bad news. It’s a latex sap that can cause a very severe skin reaction. There have been cases of people getting it on their skin and rubbing it in their eyes. And that’s very serious.”

Other common offenders include perennial sweet pea, Oriental poppies, purple loosestrife and a sweet little flower called dame’s rocket.

“Dame’s rocket is a really pretty purple flower that is growing all up and down the canyons as you drive to Estes Park now, and it’s an escaped ornamental,” Sutherland says.

Given how much effort can go into cultivating a beautiful summer flower garden here in Colorado, it might not seem like much of a problem if a handful of seeds from the city end up on Flagstaff. They’ll probably just die anyway, right?

Wrong.

Taken away from their natural environment and the predators — both insects and diseases — that keep their numbers in check, they can spread through our foothills like weeds. And that brings serious consequences.

“Plants are at the base of the whole ecosystem, and many animals are very picky or very specific on which plants they’ll eat,” Sutherland says. “Over thousands and millions of years, we have evolved an ecosystem here where plants and animals may have very, very tight relationships with each other.”
Yucca, for example, is pollinated only by the yucca moth, whose larvae feed exclusively on yucca seeds. If either were to be pushed out of the foothills, the other would disappear, as well.

“Butterfly caterpillars are notorious for being picky about what they’ll eat,” Sutherland says.

When a non-native like myrtle spurge or Dalmatian toadflax moves into our mountains, it begins to take up space in an ecosystem where it has no natural enemies and to which it contributes nothing. It takes up precious resources upon which native flora also depend — water, soil, living space — and begins a slow process of breaking the links that form Colorado’s tightly knit bionetwork.

This is especially troubling in the foothills, where microclimates in gullies and canyons permit unusual plant species — and rare insects — to flourish.

“We have some plants that are outrageously rare,” Sutherland says. “In some places, OSMP has plants that are found nowhere else in the entire state.”

When non-native plants take root, city and county land managers must go into triage mode, working to limit the spread of the plants in order to protect the ecosystem.

Decades ago, the Russian olive tree was recommended for landscaping in this area because it grew quickly and survived in Colorado’s arid climate. And so Russian olive trees were planted everywhere. Now, both the city and county expend a lot of money and staff hours working to keep these non-native trees from displacing native vegetation.

“The Russian olives will move in and push out the cottonwood trees,” Sutherland says. “Cottonwood has really soft wood, so as a branch falls off and rots, woodpeckers or other sorts of animals can make nest holes in it. Owls and hawks can make nests up in the cottonwood tree. But Russian olive has very hard, dense wood. It’s too hard for animals to make cavity nests in it. The branches are thorny and dense, so it’s not a good kind of a tree for birds to make nests in it. And on top of it, the little Russian olive fruits it produces aren’t very good wildlife food. So once you get the cottonwood trees being replaced by Russian olives, you’re taking a tree that provides enormous habitat value and replacing it with something that has no habitat or wildlife value.”

If the consequences of planting non-native plants are potentially dire, the benefits of planting native plants are tremendously beneficial. Native plants are accustomed to Colorado’s unpredictable weather — from late-spring snowstorms to dry winters to summer hailstorms — and require relatively little effort to maintain.

“Imagine that this used to be the domain of the Arapahoe and Cheyenne,” Sutherland says. “Did they go around with watering cans watering all of these little plants when there was a dry year? Were there people caring for these plants 200 years ago? Nobody was caring for them. They were looking after themselves.”

Sutherland, who practices what he preaches and grows Boulder County native plants in his garden at home, says he’s watched his garden bounce back after severe hailstorms that pounded his neighbors’ gardens into the dirt. And his garden saves him money and leaves him with more time available to enjoy his summer.

“I never water my garden,” he says.

Anyone interested in seeing a native garden can head up to Chautauqua and check out the Ann Armstrong Garden on the north side of the Ranger Cottage. Named after a Mountain Parks naturalist who died of cancer and maintained by a cadre of volunteers, it includes signage to help people learn while they admire the blooms. Gardeners are also encouraged to visit the Open Space and Mountain Parks website for a list of native flowers and tips for growing them.

For more information go to www.bouldercolorado.gov/osmp/nativegardens.

Respond: info@boulderganic.com

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