Green Scene

It seems like there’s no end in sight for invasive plants


Returning to my invasives, which I started talking about last week, the flowerbed in the backyard looked absolutely fabulous this spring. It was filled with the delicate fronds of the Ostrich fern (Matteuccia struthiopteris) that I had so blithely bought years ago.

And that was the problem. They loved the growing conditions of relative shade and regular moisture. They loved it so much that they were overgrowing all the other plants that I also planted in that bed.

Once again, this reproductive abundance is due to vigorous underground rhizomes, which can travel several feet before putting up another plant.

Bravely, I went out with a pitchfork and started uprooting them. It is easily done, except where they entwine themselves with other plants. The real challenge, however, will prove to be finding and removing all those rhizomes.

With the major overgrowth removed, going on a fern hunt once a week for the next year or so, should eliminate most of the remaining problem.

Bryophytes — mosses, liverworts and hornworts — were the first land plants. While their oldest fossils can be dated to the early Devonian (circa 417 million years ago), there is reason to believe that they evolved even earlier, perhaps as much as 470 million years ago. Devonian-era ferns became the dominant plants during the Carboniferous (369 to 299 million years ago). Their organic remains have contributed greatly to today’s coal, oil and natural gas deposits.

Reproduction in plants is remarkably complex and is termed “alternation of generation.” There are two separate cycles — one requiring a male and female component and giving rise to a plant with a full complement of chromosomes (diploid), the other cycle requires spores, giving rise to half the full number of chromosomes (haploid).

The fern forms generally familiar to us have their spores prominently displayed on the underside of its fronds. In the case of the lovely green ostrich fern, the fronds are actually sterile, but the plant puts up a fertile stalk in its center in mid-summer.

The genus name Matteuccia honors Carlo Matteucci, a 19th-century Italian physicist who pioneered studies in bioelectricity — ion flux, which mediates communication between cells. The epithet derives from the ancient Greek strouthion for “ostrich,” and pteris for “fern.”

Wildflowers have a special place in our hearts. They are the plants which do not require the helping hands of gardeners and come up lavishly at their appointed time. I have inherited my share of them, and I used to be thrilled with their flowering.

But while busy eliminating other invasives, I realized that I was no longer happy with some of the wildflowers in my garden. While weeding, I started forking up the clumped roots of Ageratina altissima (formerly Eupatorium rugosum) or white snakeroot (family Asteraceae) which, to my consternation, is the focus of October’s EcoFlora Challenge.

Riverdalians might be happy to know that this plant is found all over the neighborhood, both in gardens and in untended areas where it provides nectar and pollen to a large variety of insects, including monarchs (Danaus plexippus), ruby tiger moths (Phragmatobia fuliginosa), and the blue-winged scoliid wasp (Scolia dubia).

Insect tracks can be seen frequently on snakeroot leaves. Some are made by leaf miner larvae, Liriomyza eupatorii, which develop between the leaf’s outer layers.

Nancy Hanks Lincoln, Abraham Lincoln’s mother, died of milk sickness. Apparently cows grazing on the white snakeroot accumulated the toxin tremetol in their milk, which poisoned anyone drinking the milk or eating the meat. Many settlers of the Midwest who were unfamiliar with the plant and its dangers were victims.

I have mixed feelings about the final invasive to be discussed here, one that can be seen along Westchester highways, Celastrus orbiculatus (oriental bittersweet). On the one hand, it creates gorgeous green draperies covering large groups of trees and shrubs. Its beautiful red berries encapsulated by an orange husk are a familiar feature of the autumn landscape and are frequently used to make wreaths.

On the other hand, those selfsame, gorgeous green draperies will eventually smother and kill the plants underneath.

A member of the largely tropical family Celastraceae, the bittersweets are related to the garden workhorse, the Euonymus American bittersweet, Celastrus scandens, is a native. And while it also can damage trees, it is far less aggressive that the oriental bittersweet, native to China, Korea and Japan. It was introduced to the United States in the 1860s, and is driving C. scandens to extinction.

David Burg, a naturalist and founder of Metro Wild, explains that the Bradley Method of removing invasives has been very helpful in their work. It features, counterintuitively, removing invasives in the less overgrown areas, gradually moving into areas of greater intrusion. Moving slowly outward allows the relatively undisturbed areas to regenerate.

Next year I will follow up on my gains, monitor the invasives better, and replant!

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