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I spent a couple of weeks this spring in Europe birdwatching and finding wildflowers. My family was along and we shared many wonderful sights and experiences together, although at other times they would head in one direction and I the other.

One afternoon in France, we visited Chateau de Chenonceau built on the River Cher. The formal grounds were surrounded by forest. The lure of the birds and wildflowers in bloom was irresistible. I sauntered off following a trail that lead deep into the woods while the rest of the family toured the gardens and buildings. While I was on the trail, standing with a wildflower guide and pondering some new species, I met another hiker from the local area. We exchanged greetings and quickly recognized that we were both interested in the spring flowers that were in bloom.

We also promptly learned that neither of us knew much of each other's language. My French doesn't extend much beyond bonjour and cafe avec le lait, and her English included hello and "What is that wildflower?" She had spent some time visiting this country enjoying spring wildflowers in the Smokey Mountains. We did have a common language in the Latin names of plant species and families, and with a little sign language she was able to point out many plants that I didn't recognize.

The two of us puttered about finding wildflowers that were in wonderful flower. Some I could identify to the genus, including several violets and a primrose or two. My new naturalist associate filled in the species.

Some of the wildflowers in the Loire Valley forest I recognized.

One in particular was obviously in the mustard family. It had the characteristic flowers with four broad white petals, and blossoms held above the forest floor on long stems. My friend also knew the plant. She pulled off a leaf, crushed it, and let me smell the distinct fragrance of garlic.

Again with some French that I did understand and an abundance of hand gestures and pantomime she transmitted the message of how the plant was valued as a flavoring in the local cuisine. This spring species was a special treat for the French and others in Europe.

I looked around. There were occasional small patches of the plant scattered under the new-leaf canopy. It wasn't abundant, but neither was it rare. It seemed to be well-behaved, sharing space in the rich woods with an ensemble of other equally well mannered neighbors. The place reminded me of many similar places here in western Pennsylvania with a diversity of wildflowers each inhabiting their own niche and not intruding on the living space of others.

Finally, I realized that my appointed time to rejoin the family was at hand. I expressed my thanks for the companionship and help learning new plants and said au revoir.

I tell you this little vignette to set a stage for a larger story. It's an ecological story about plants that are well-mannered natives in one place in the world, but are serious pests in other places where they have been introduced.

With apologies to Dickens, my thoughts after seeing the little white-flowered plant in the French woods were; "It is the best of wildflowers; it is the worst of wildflowers."

The plant my friend and I found in the Chateau de Chenonceau forest was garlic mustard (Alliaria officinalis), a native to Europe. A biennial, the plant grows a rosette of leaves the first year and then flowers and seeds the second. As I found, in Europe garlic mustard is found in patches throughout woodlands much like we find patches of trillium or trout lily in our North American woods. The populations of the plant are kept under control by nearly three dozen species of insects that feed on the pungent garlic scented leaves, stems and roots of the plants, and by a suite of fungal diseases. If garlic mustard begins to increase, predators increase to feed on the bounty, and a balance is reached keeping the plant in check. In its native haunts, the little white wildflower shares the forest floor with all the other species.

The leaves are rich in vitamins A and C and thus the popularity of the plant as a food and seasoning. The English, Welch, and French all incorporated the fragrant leaved herb in a variety of dishes, especially salads. It's no wonder that in the late 1800's garlic mustard was deliberately brought to North America by European immigrants wanting to enjoy a bit of their native cuisine in their new home. What they didn't bring were the bugs and diseases that controlled the plant in its native haunts.

By the early 1900s the new visitor had hopped out of kitchen gardens, and was growing in the wild from Quebec to Virginia. Being a plant of shaded locations, its march across the eastern United States slowed, since during those times forests had been significantly removed. Since then, the woodlands have regenerated and more habitat has become available for garlic mustard. The plant took advantage of the situation, and without its host of predators, a "good" spring wildflower of Europe has become a "bad" invasive weed of North America.

Over the last couple of decades invasions of garlic mustard have spread through eastern forests into the heartland of the Midwest. Just about everywhere I go in the spring, garlic mustard is there. Plants can be found in full flower from the deep woods of Ohiopyle to the bottom of the hill in my own Glenshaw back yard to the sands of Presque Isle in Erie.

You might think -- well, that's not so bad to have another flower to add to our diversity. However in this case, the invasion is so dense and widespread that garlic mustard is crowding out the natives that share the rich woodland habitat. The fragrant herb gets a head start by retaining rosettes of green leaves over the winter and rapidly emerges in the spring to shade out other species such as trilliums, hepaticas, spring-beauties, trout lilies and many others.

The problem doesn't stop with the loss of just some native plants. Think about it. Plants are often the host for specialized insects that feed on just that species. If the species is eliminated, then the insect goes along with it. This is the case for several butterfly larva that have specific food plants. Take that a step further. If the butterfly is the only pollinator of a plant, without the butterfly to help in reproduction another plant is lost from the forest floor. One break in the web of life sends shockwaves through the whole web.

Garlic mustard is not the only introduced plant that has besieged our landscape. Japanese knotweed covers vast areas along creeks, streams and rivers. Most of the islands in the lower Allegheny River and the Ohio River are dense thickets of knotweed and nothing else. Gone are the ferns, green dragon, jewelweeds, and other plants native to riverine habitats. Purple loosestrife covers acres and acres of coastal marsh on the Atlantic Ocean and inland in marshes and swamps, pushing native species aside and causing local extinctions of plants and animals.

The invasive invasion isn't limited to plants.

The European starling was brought to New York's Central Park in a good-hearted but what proved to be foolish endeavor. In the 1890s an organization devoted its time to bringing to the United States all the birds mentioned in Shakespeare's works. One hundred starlings were released. A century plus later, the millions of European starlings crowding out native cavity nesting birds are the kin of those 100 birds.

The moral of the story?

We need to be far more careful with what plants and animals we introduce from other lands. Some of these are well-intentioned experiments, but most often they simply don't take into account all the ramifications and we are left with an ecological mess.

The workings of the natural world are exceedingly complex. Seldom are we able to confidently predict the outcomes of fiddling around with nature.

Paul g. Wiegman is a freelance writer, photographer and naturalist born and raised in western Pennsylvania. Write to him c/o Tribune-Review, 622 Cabin Hill Drive, Greensburg, PA 15601; or e-mail him at pgwphotography@earthlink.net.

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