ALTERNATIVES FOR INVASIVE PLANTS
Dr. Leonard Perry, Extension Professor
University of Vermont
When choosing plants for your garden, become knowledgeable about species that may be invasive, and consider using alternatives instead. This has become one of the most important topics currently in gardening.
Often invasive species are introduced from other countries through gardening, but they may even include aggressive native species from other regions. This doesn't mean that all introduced plants are invasive, rather the contrary. Invasive species are usually ones that are spread by seeds, often by birds, to take over both managed landscapes and natural areas. Once established they are difficult to control. They crowd out other desirable or native species, often eliminating them. Such habitat destruction in natural areas can have negative impacts on wildlife, taking away their cover in winter and sources of food.
Five common invasive ornamental plants, along with some suggested alternatives, are covered in a publication from the Connecticut Agricultural Experiment Station, Alternatives for Invasive Ornamental Plant Species, by Timothy Abbey. They include the perennial purple loosestrife, the tree Norway maple, and the shrubs autumn olive, Japanese barberry, and winged euonymus.
The purple loosestrife (Lythrum salicaria) is perhaps the most commonly known invasive plant, and is the reason for many states having laws and regulations on such plants. It was introduced from Europe in the early 1800ís, and is the spiked flower about three feet high seen blooming in wet areas (such as marshes and roadside ditches) in mid to late summer. This genus should not be confused with another loosestrife (Lysimachia) which spread aggressively by roots.
Alternatives to the purple loosestrife, also with purple flowers, include many cultivars of bee balm, coneflower (Echinacea), and swamp milkweed. These get about the same height and give a similar effect planted in mass. Taller is the Joe-pye weed, which prefers moist to wet soil, as does the swamp milkweed. The bee balm need moist soils. The coneflower grows in moist or dry soils, but just needs well-drained soil.
The Norway maple (Acer platanoides) was introduced from continental Europe in 1756. Dense stands of this tree can crowd out others, including the sugar maple. It and its cultivars are widely planted in urban and residential areas as they tolerate harsh conditions. Native alternatives to this tree are both the red and the sugar maples. The red maple also can tolerate wet soils.
The autumn olive (Elaeagnus umbellata) was introduced from Asia around 1830. It has been planted for its silvery-white leaves, fragrant flowers, red fall fruits (spread by birds) and ability to grow under harsh conditions such as low fertility and drought.
Bayberry has a similar size and habit to the autumn olive, and also tolerates poor soils including salty ones. Its small gray berries in winter provide food for birds. Winterberry has bright red berries in late fall, attractive to birds and useful for decorating. While bayberry and winterberry are native to the New England area, fothergilla is not. It has white flowers, nice orange to scarlet fall color, and is smaller at two to three feet high.
Japanese barberry (Berberis thunbergii), arriving in our country from Japan in 1864, is commonly found in landscapes, especially as one of the red-leaved cultivars. The red fall fruits are attractive and spread by birds as well. Bayberry and winterberry are also alternatives to this plant, even though larger in size. Chokeberry is another large native alternative, with berries for birds in winter. Highbush blueberry provides berries and cover for birds in summer, as well as excellent red fall color. The blueberry needs acidic soils.
Winged euonymus (Euonymus alatus), introduced from China around 1860, it is so called from the winged appendages along stems. It also is known as burning bush from its bright fall color. This plant can invade and dominate a natural forest understory. Once again, consider as alternatives the same plants as for barberry or autumn olive. Summersweet clethra is another possible choice, preferring moist to wet, and acidic soils. It provides pale yellow to golden fall color.
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