Planting for tomorrow: Replacing aggressive species to promote diversity

While we are blessed with a vast and varied country and a deep heritage of local plant species, a visitor from the Moon would be forgiven for thinking our national flower is the Stella D’oro daylily and our national tree the Bradford Pear. Driving the streets of suburban communities from Portland, Oregon to Portland Maine, one is apt to be overwhelmed by a startling sameness in the vegetation, despite large differences in climate and ecology.

“What drives me crazy is seeing the same twelve plants used everywhere," says local native plant expert Cheryl English says. "We don’t garden according to where we live. We garden according to where are our ancestors came from. We don’t even have a concept that there is this body of plants as a culture.”

Our native botanical assets are remarkable. The Eastern United States in particular is home to an astonishing diversity of species, including hardwood trees and wildflowers.

But American gardeners are beginning to get hip to the value of native species and their importance to local ecology. The dependence of Monarch butterflies on native milkweed plants is one example that has caught the public’s attention.

Often the issue is framed as a choice between native and exotic plants or native and invasive plants. Although this is an important part of the conversation, it's more important to focus on increasing overall ecosystem diversity rather than trying remove non-native or invasive plants entirely, which may prove to be an impossible task.

The following are some "do and don't" suggestions based on the idea that preserving local wildlife and increasing visual interest in our gardens is something that most of us should be able to get behind.

“You can’t have too much diversity, like any other aspect of the world," says English. "If you dig up a piece of untouched prairie somewhere there are dozens of species there/ Mimicking nature not only supports local ecology, it also makes life more interesting."

Don’t plant: Vinca, Lily-of-the-valley

Lily-of-the-valley. Photo credit: Liz West via Flickr.

Vinca (
Vinca major) and lily-of-the-valley (Convallaria majalis) are common landscape plants are widely used as flowering groundcovers. The advantage of these plants is their ability to spread quickly to occupy and even stabilize a patch of ground, as well as their ability to tolerate shade. However, this is also the problem. Give them a foothold and they'll soon overrun your garden and make their way into nearby woodlands, crowding out native ground flora.Vinca. Credit Ferran Pestana via Flickr.

Plant instead: Sweet Woodruff, Wild-Strawberry, Wild Ginger, Sedum, Solidago Flexicalis

There are a number of shade loving plants that can replace Vinca and lily-of-the-valley. Sweet Woodruff (Galium odoratum) is one readily available non-native plant that spreads in shady areas but doesn’t take over. And it dries nicely into a fragrant fall bouquet.

As for natives, there are some options.

Wild Strawberry
(Fragaria virginiana) comes in several forms. These don’t produce grocery store sized strawberries, but tiny, very flavorful berries. With a little care, these plants will spread on their own. Like other food plants covered here, they may be used either as food for humans or food for wildlife or—as is most common—a little of both.

Sedum (Sedum spp.) come in a variety of shapes and sizes, including the native sedum ternatum. These succulents do well in full sun. However, they can also tolerate some shade. All sedums will flower, but they are generally used for their foliage that looks especially good when set off against rocks. Varieties of dwarf sedum in particular are often set between stepping stones as a drought-hardy substitute for grass.

Zig-zag goldenrod (Solidago flexicaulis) is a shade-tolerant flowering plant. Although goldenrod is often blamed for allergy problems, this is usually caused by ragweed, which blooms at the same time and is pollinated by the wind (goldenrod is pollinated by insects.) These plants can be employed to provide more color in the same area as above-ground covers. They produce yellow flowers between July and September and attract butterflies. Importantly for many gardeners in the Detroit area, the plant tolerates clay soil.

Wild Ginger (Asarum canadensis) is another native plant that can function as a groundcover in shady areas. The plant produces strange, fleshy red flowers at ground level that look like miniature skunk cabbages. But the real attraction is the thick cover of heart shape leaves that emerges as it spreads. It’s not related to true ginger–although early settlers and Native Americans used the root as a spice and to make an antibiotic compound for treating wounds. It's also a host plant for the Pipevine Swallowtail Butterfly.

Don’t Plant: Bradford Pears

Chances are this advice might be too late. The Bradford Pear (Pyrus calleryana) is a commonly planted trees that many sayBradford pear. Credit: Jay Sturner via Flickr.

smells like rotting fish when in bloom. They have been planted almost everywhere for their relatively columnar shape and pretty, white (if stinky) flowers.

Unfortunately, these trees split easily and need to be constantly trimmed or replanted. What’s worse, they make a prodigious amount of small fruit that birds eat, only to deposit seeds across the landscape and plant new stands of wild trees that have caused the tree to be considered invasive.

Plant instead: Sweet Gum, Serviceberry, Sassafras

There are any number of fantastic indigenous trees that can planted in place of a Bradford Pear. Sweetgum. Credit: Wikimedia commons.

Sweetgum (
Liquidambar styraciflua) might be especially appealing since they have a distinctly upright habit. Their brilliant autumn foliage is a plus as is the fact that it provides food for the luna moth, a lepidopteran of mythological dimensions. Although some people complain about the spiky seed pods the tree drops in autumn, they don’t smell and can be easily cleaned up. They are also brilliant fodder for fall craft activities.

Serviceberry (Amelanchier arborea) is a native landscape tree that has delicious edible fruit. They function well in a variety of soils. Although they’re often multi-stemmed trees that will be less compact than Bradford pears, their small stature allows them to fill a similar space. They have beautiful bark and structure. Once you begin to recognize them, you will see them and their edible berries all over suburbia, and you can forage from their fruit in mall parking lots and subdivisions as those around you question your sanity.

A more outside-of-the-box substitute might be Sassafras (Sassafras albidum). This is a tree or bush that often grows on the Sassafrass. Credit: Kristine Paulus via Flickr.

edges of forests. Interestingly it has leaves of a variety of shapes, some of which resemble the mitten of our own beloved home state. As a landscape plant it can be pruned to grow upright and will produce brilliant yellow and red fall foliage while providing food for birds and serving as a host plant for spicebush swallowtail butterflies.

Don’t Plant: Burning-bush

Burning-bush. Credit: Wikimedia commons.

Burning-bush (
Euonymous alatus) is a plant of Eurasian origin that has been disseminated widely for its vibrant red leaf color in fall. The rest of the year it’s a basic-looking shrub that has the unfortunate habit of spreading into woodlands and crowding out the native understory in a manner similar to honeysuckle. It also doesn’t respond particularly well to pruning, meaning it will either outgrow its allotted space or lose the fall color it was purchased for.

Plant instead: Shrubby Dogwood, Viburnum, Elderberry

Luckily there are scores of native, eco-friendly bushes that can be used to replace burning bush or other shrubs. Among them is a whole class of plants in the viburnum family, like the red-berried Highbush Cranberry (Viburnum trilobum), that grow to varying heights, have great flowers, beautiful deep green foliage and fruit that although generally not edible by humans, is appreciated by other wildlife.Highbush cranberry. Credit: Andrew Kaz via Flickr.

“They are excellent pollinator plants, a host plant for the hummingbird clearwing moth and have great fall color,” says English. “If you look at viburnums compared with hydrangeas in terms of landscape value and functionality, viburnums win hands down.”

Although most of us are familiar with dogwood trees, shrubby dogwoods are less commonly known. But there are a number of these plants that make great additions to the garden, Red-osier dogwood. Credit: Wikimedia commons.

especially for their bark in winter-time. These include, red-osier dogwood (Cornus stolonifera) whose branches are often cut and used for decorative arrangements during the holidays. These can be pruned in spring, although it’s best to remove only twenty-five percent of the branches at a time to encourage new shoots, which have a brighter color than the old ones. Shrubby dogwoods do well in heavy soil, but do best in wet conditions so they may be good candidates for wet spots or rain gardens.

Finally—saving the best for last here folks—elderberry (Sambucus canadensis) is an overlooked native plant that possesses beautiful blooms and berries. The fruit can be processed into jam or left for wildlife. Elderberry provides food for many organisms from birds to moths to beetles. They grow tall—up to 12 feet—so it’s best to plant them somewhere they won’t be in the way. They make an excellent hedgerow plant.

Elderberry. Credit: Andy Rogers via Flickr.

My friend Patrick Crouch from 
Earthworks Urban Farm says that his elder shoots live for 5-7 years, at which point they need to be pruned to the ground. This kind of a maintenance might take some getting used to—as opposed to pruning a yew bush into a box-shape—but it’s probably less work overall and produces a more interesting effect.

For more information, check out this advice on how to incorporate natives into your garden from Michigan State University Extension. You can also check out the Midwest Invasive Species Information Network.

Brian Allnutt is a gardener and co-owner of Detroit Farm and Garden. He writes about nature, gardening and open space issues among other things.

This story is a part of a statewide Invasive Species Community Impact Series edited by Nina Ignaczak. Support for this series is provided by the Michigan Department of Natural Resources.
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