Friday, May 21, 2010

What's in the Fill?

Yesterday I spent the day at a workshop at the Seacoast Science Center, which lies within Odiorne State Park on the shore of the Atlantic Ocean. The water shimmered under a blue sky, the Isles of Shoals looked close, students visiting the Science Center clambered over the exposed intertidal rocks. The focus of our workshop, however, was landward and less idyllic.

Invasive plants. Sometimes it seems hopeless trying to remove existing infestations and repel new ones. The workshop speakers, experienced in both, were determined and motivational. It is worth the effort they said -- to restore and maintain natural habitats, to maintain native plants that an array of native insects and other wildlife are adapted to, to ensure that natural systems keep functioning. The monarch butterfly is an example. It depends on common milkweed for its life cycle, but in some places in the northeast the invasive pale swallow-wort (also in the milkweed family) is taking over fields and crowding out native plants. Although the two plants are from the same family, monarchs cannot use swallow-wort.

A panel of three focused entirely on Japanese knotweed. The stems look like bamboo. It forms dense stands and is one of the most difficult invasive plants to control. Mowing spreads the plant farther. Knotweed spreads quickly along waterways and roadways; its rhizomes can move long distances undetected underground, extending up to 30 feet and 10 feet deep! This is one plant that most everyone agrees can only be controlled with repeated treatments of herbicide if the stands are more than a few stems. To avoid use of chemicals, small infestations must be removed as soon as they are detected.

Many people may wonder why there is such concern about invasive plants. A knotweed here, a buckthorn there, a few garlic mustard, burning bush, or honeysuckle in the yard. It's about the numbers. One of the most pernicious traits of these plants is that they spread very, very quickly given the right conditions.

Early detection and rapid response was the message of the day, especially if one goal is to avoid use of chemicals. Once an infestation gets beyond a certain size, hand pulling or digging becomes ineffective or incredibly labor intensive.

Another interesting discussion at the workshop is the movement of material from place to place: fill, gravel, mulch, loam, compost, leaves. It is now known that many invasive plants are being moved from property to property and along roads in these materials. My dad and I just discovered last weekend that the source of garlic mustard on Winterberry Farm was probably in the loads of leaves that he got from the town for use as mulch.

A few recommendations from the workshop:
  • Know the source of any fill, mulch, loam, or other material brought to your property
  • Get to know the invasive plants in your area and employ early detection-early response
  • Avoid staging or piling debris on or mowing areas of invasive plants, unless it is part of a control effort, as you might spread the invasives farther
  • Remember to focus on the goal: preserving our natural heritage -- the biological diversity native to the region
I'll be watching for monarchs flitting among the common milkweed.

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