New Hampshire has a relatively long list of invasive plant species. The majority of backyards and roadsides have a least a couple of different invasive plants represented. It is well-known that invasive species reduce biodiversity by outcompeting native plants and animals for resources. They are better competitors because they emerge earlier in the spring, grow rapidly, and are impacted by few, if any, natural predators. When invasive plants are allowed to grow unchecked, many native plants and the wildlife species that rely upon them suffer.
However, invasive plants can provide some benefits to some species. Invasive species such as autumn olive, oriental bittersweet, and honeysuckle produce fruit that is relished by a handful of fruit-eating bird species. In fact, planting autumn olive was once encouraged as a means of creating wildlife habitat before it was realized that the shrub has the ability to spread quickly on its own. The birds that eat the fruit of invasive plants benefit from having an abundant food source in the fall and winter, which increases their survival. Invasive plants can also serve as a source of pollen and nectar for a variety of insect species. Many bees will readily forage on invasive plants like Japanese knotweed or spotted knapweed.
So, should we be leaving invasive plants in our landscapes or eliminating them? While invasive plants do benefit a few species, they are a detriment to many more. Even though frugivorous bird populations may grow in response to an increased number of food resources, many other species suffer from habitat loss. If you are concerned that removing the invasive plants from your property will eliminate food for the wildlife in your backyard, consider replacing them with native plants. There are a tremendous number of native trees, shrubs, and perennials that bloom and produce fruit late in the season, are enjoyed by wildlife, and do not take over natural areas.
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