Garden Space Invaders

By Jill Hahn//Special To The Tab

 

If you're like me, you started thumbing through garden catalogs in the dark days of early February, ogling the lush photographs and dreaming of how all those perfect, blooming plants would look in your own yard. Of course, your yard was covered with 2 1/2 feet of rock-hard snow in early February, and there wasn't enough daylight to grow a mushroom. Sending photos of bright flowers and vivid fruit to New Englanders in February is like sending a frosty six-pack to a recovering alcoholic. Common sense might just go out the window. And the choices you make as you admire those glossy advertisements can have an impact far beyond the corners of your yard.

 

The 10 most unwanted

Here are the top 10 species of plants that are listed as unwanted by the Massachusetts Natural Heritage and Endangered Species Program:

·      Oriental bittersweet Celastrus orbiculata

·      Purple loosetrife Lythrum salicaria

·      Autumn olive Elaeagnus umbellate

·      Japanese, Morrow's, and Amur honesuckles Lonicera sp.

·      Multiflora rose Rosa multiflora

·      Norway maple Acer platanoides

·      Garlic mustard Alliaria petiolata

·      Shining and common buckthorns Rhamnus fragula, R. cathartica

·      Common reed Phragmites communis

·      Common and Japanese barberries Berberis vulgaris, B. thunbergii

 

Consider:

 

"Lonicera maackii [Amur honeysuckle]... produces masses of white flowers that mature to yellow followed by a profusion of 1/4" bright red fruit persisting into winter... adaptable to poor soils..." (Nature Hills Nursery) "This climbing Bittersweet Vine produces sunny yellow seed pods that give way to bright red, decorative berries... thrives in the poorest of soils. Songbirds love to gather around this attractive plant, and so will you!" (Michigan Bulb Company)

Wow, those plants sound great! But what the catalogs don't tell you is that these two species are on the Massachusetts Natural Heritage and Endangered Species Program's "Ten most unwanted invasive species" list, villains that threaten the wellbeing of the native plants and animals that have defined our natural landscape for millennia.

An invasive species is one that, once established, manages to spread in numbers and space to the exclusion of other plants. Alien invaders, those imported from other countries, tend to be especially damaging because the predators that might keep in check in their native habitat don't exist here.

If you look around your yard, you will likely find that most of the familiar plants that define your personal landscape are actually alien species. That rhododendron just bursting into bloom is as likely to hail from Japan as from North Carolina. The tulips came from Central Asia, the daffodils from the Mediterranean. Even the grass species growing in your lawn were introduced from Europe. Although they are not native to the U.S., most of these species are well-mannered and don't present a problem to the forests and meadows of New England. What sets such species as the honeysuckle and bittersweet apart is that they are not content to stay where they are put. The very attributes that make you want to buy them (thrive in the poorest of soils, attractive to birds) are what make them a threat.

Five key biologic traits characterize invasive species: 1) they produce large quantities of seeds; 2) they have effective dispersal mechanisms; 3) they are readily established; 4) they grow rapidly; and 5) they are effective competitors. The birds, for example, that flock to your bittersweet vine to eat its berries become dispersal agents that carry its seeds to your neighbor's yard, our woods and roadsides, the local Audubon preserve. Every manager of natural spaces in our state is currently waging war against spreading stands of alien invaders. When the diversity of native plants becomes overwhelmed by stands of a single, introduced species, it can cause the disappearance or extinction not just of those outcompeted plants, but of the animals that depended on them as well.

So what can you, the responsible gardener, do? Before you make an impulse buy from a garden catalog or center, do a little research. There are many sites online that can help you identify, and avoid, alien invaders (The New England Wildflower Society has a well-researched list, as well as a list of native alternatives, http://www.newfs.org/conserve/invasive.htm). To get you started, here are a few plants you should not buy:

Goutweed, or snow-in-winter (Aegopodium podagraria), a variegated, three-leaved groundcover that's almost impossible to pull out because it propagates by easily-fragmented runners; those non-native honeysuckles(Lonicera Morrowii, L. tatarica, L. Maackii, L. x bella & L. japonica);Porcelain Berry (Ampelopsis brevipedunculata); Yellow Flag Iris (Iris pseudacorus); Burning Bush (Euonymus alatus), that ever-popular large woody shrub that turns bright scarlet in autumn.

Be especially suspicious of plants touted as able to grow in all conditions, or as good for erosion control. Become familiar with the top 10 unwanted species and eradicate them ruthlessly whenever you see them. Some of them will be obvious weeds, while others hold pride of place in many local gardens. It hurts to look at your beautiful burning bush specimen as an alien enemy, but that shrub doesn't look so beautiful when it's monopolizing the understory of the local forest.

Now excuse me while I go dig up the prickly but lovely Japanese barberry bush that's screening my compost bin, and leap back into my losing battle with the Japanese knotweed that is marching its way up my backyard. Thank goodness I wasn't the one who decided that might be a nice ornamental plant and set it loose on an unsuspecting Newton.

Jill Hahn, a Newton Highlands resident, is a biologist, a writer, and a mom. All three roles contribute to her interest in environmental issues. She can be reached at jkkhahn@comcast.net.

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