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Garden Matters: Invasive Plants by Erno Bonebakker

Mary Holman’s article in the June Calendar described the potential human health issues caused by ticks. In this article we will discuss another aspect of the tick problem, the exotic and invasive plants that contribute to the explosion of the tick population on Chebeague. A small portion of the exotic plants that we humans have imported from other places for their agricultural or decorative value, or by mistake, become invasive pests. Some we call weeds, but others cause less apparent but nevertheless signifcant problems. Offcially, an invasive plant is defned as an exotic (from away) that is likely to cause economic or environmental harm or be harmful to humans. A characteristic of troublesome invasive plants is that they spread rapidly once established and outcompete the existing native plant species. In the Casco Bay region, some of the most widespread and troublesome invasive plants are Oriental bittersweet, Japanese barberry, bush honeysuckles, common reed, and black swallow wort. Each of these species is troublesome for a unique reason. Many additional species are considered invasive, and more are expected to arrive as our climate changes. In addition, some species such as crown vetch are invasive in particular situations, although not considered a regional problem. Roughly two thirds of invasive plant species were purposely introduced, while the remainder arrived by accident. For example, the European strain of common reed was introduced accidentally through its use as a packing material for shipments from Europe during the nineteenth century. It has since spread—to the detriment of the less aggressive native strain. The big problem with Japanese barberry is that it hosts ticks that carry Lyme and other diseases. Research by the Maine Lyme Disease Swee’pea Vintage Signs Order your custom chalk painted and framed wooden sign for your home or cottage. Interior or exterior signs available. Great gift for new home owners, weddings and as a baby gift!

Research Laboratory has shown that Japanese barberry and bush honeysuckles offer an enhanced habitat for ticks and the small mammals that host tick nymphs. This impact on human health creates an additional reason to manage the spread of invasive plants on our island landscape, not only for the sake of the native habitat but also to improve the health of our human population. Black swallow wort, on the other hand, endangers the beloved monarch butterfly. Swallow wort, a native of southern Europe and a member of the milkweed family, is mistaken by monarchs for common milkweed, the sole plant on which monarchs lay eggs and their caterpillars feed. In addition to overwhelming native plants once it is established, swallow wort is poisonous to monarch caterpillars. Its wind-dispersed seeds make it an especially worrisome threat and, thus, an important one to manage aggressively when frst detected. Oriental bittersweet is a fast-growing perennial vine that can overwhelm and kill large trees, as it has done on Little Chebeague. Clipping the vines can keep it in check. It is so widely distributed in our region that it cannot be permanently eradicated, since birds tend to eat the seeds, get indigestion because of their exotic nature, and quickly drop them on nearby land. Japanese knotweed must be disposed of with care, as the root fragments easily resprout. Cuttings and roots are best placed in the garbage compactor, where they will eventually be burned (for energy), rather than dropped in the brush dump, where they may be recycled, spreading this pest to new sites. We are burdened with the often innocent mistakes of our ancestors in the case of invasive plants, but doing our best to practice good stewardship today will hopefully leave Chebeague a healthier and more vibrant place for our descendants. Island Riches R Flowers, Vegetable Plants, Silver Jewelry, Framed and Unframed Art, Handcrafts and Art from Island Artists, Toys, Gifts for Any Occasion. Phone: (207) 846-4986 If We’re Home, We’re Open!

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AUGUST 2016 CHEBEAGUE ISLAND COUNCIL CALENDAR