Even if they are pretty or smell divine, resist the temptation to plant them.
If you have ever seen a weed take over your whole garden or yard, you have seen invasive plants in action. The following invasive plants look like common garden plants. However, they are capable of quickly multiplying and crowding out native plants in open spaces, like woodlands and wetlands.
Purple loosestrife is a perennial herb that is native to central and southern Europe and many parts of Asia. Its square, woody stem characterizes it, and its magenta blooms. Purple loosestrife takes over wetland areas, where it outcompetes with native plant species, which provide better nutrition to wildlife. Regulations in Minnesota, Illinois and Wisconsin prohibit buying and selling purple loosestrife. Several insect species have been approved by the U.S. Department of Agriculture for controlling it on a large scale. Although it was introduced in the 1800s as an ornamental plant, it’s not a good choice for gardens today. Native alternatives to purple loosestrife are purple aster, New England aster and bee balm.
This ground cover is popular in North America, but unfortunately it escapes from gardens easily. It is known to crowd out forest floors by preventing other plants from receiving enough sunlight. If you are set on using English ivy as a groundcover, know that it must be trimmed back often in order for it not to spread. If you are willing to prune your English ivy regularly, it poses a minimal risk of spreading. A native alternative to English ivy is Allegheny spurge (Pachysandra procumbens). Allegheny spurge is a sturdy groundcover with green foliage.
The yellowflag iris is easy to mistake for native irises. It is a wetland plant that colonizes into monotypic stands, crowding out native wetland plants. Yellowflag iris spreads easily from gardens to neighboring lands. Although it colonizes in wetlands, yellowflag iris is very drought-resistant. It grows in both saltwater and freshwater wetlands. If you are planting irises, be sure that you are planting native iris cultivars, as yellowflag iris is highly invasive.
Also known as “wild snapdragon,” yellow toadflax looks a lot like native snapdragons. They grow horizontal, interconnected root systems, and therefore grow in clusters. Yellow toadflax thrives in moist to well-drained soil. Though yellow toadflax was introduced to America as an ornamental plant, it is considered to be an invasive weed. Plant native snapdragons, rather than yellow toadflax.
Unlike the sweet smelling vine honeysuckles that are ever-so-delicious, bush honeysuckles are invasive plants that are native to Asia. They are deciduous bushes that are able to thrive in many environments, from wetlands to woodlands. The woody bushes grow in thickets, and can easily dominate the habitat where they grow. If you are introducing honeysuckle to your garden, be sure that you are planting native honeysuckle vines, rather than honeysuckle bushes.