This is a subject that is both important and confusing. Important because there are many native species of plants, trees, vines and shrubs that are currently threatened by the proliferation of invasive, non-native species, and confusing because a lot of people don’t really know what constitutes the differences between the two.
As gardeners, we’re tempted by the new and exotic – something different from the same old species to which we’ve become accustomed – to set apart our gardens from the rest and make them more exciting. There is a hidden danger in that quest, however. A good example is a bird most of us are familiar with: the European starling. This is an introduced species, a “non-native” to North America, one that for the most part is considered a pest. Its presence has had an incredible impact on our “native” species in the competition for food and nesting sites. It all started so simply: In 1890, 60 of them were released in Central Park so that all the birds Shakespeare had written about would be represented as a connection to the Old World for European settlers. Little did we know that in just 60 years they would make their way all the way to the Pacific!
To understand the term native, just think of North America as it existed before the arrival of the first European settlers: whatever existed then in North America is considered to be “native” in terms of horticulture. Some names are dead give-aways, like Oriental bittersweet, as opposed to American bittersweet. Also, don’t think that just because something is a weed or wildflower that it’s native, because that’s not always the case.
It would be hard to imagine being without some non-native plants such Queen Anne’s lace or butterfly bush, but everyone needs to pay attention to what is planted in their yards and allowed to flourish.
Good or bad?
Two examples of popular plants for birds but which have a down side include: Cotoneasters and bush (Tatarian) honeysuckle. Cotoneaster produces tons of berries the birds love and makes an excellent groundcover but it is now considered invasive on the Pacific Coast, so care should be taken when considering this plant. And while bush honeysuckle, especially tartarian (Lonicera tatarica), is both beautiful and beloved by birds, it is crowding out native shrubby dogwoods and viburnums. Even scarier is the research from a recent study on cedar waxwings that showed the normally yellow-tipped feathers on this spectacular bird turned orange after consuming the orange and red fruits of this seemingly harmless honeysuckle. Since birds use the colors of their plumage as badges of gender and species recognition, a deviation such as this could have serious implications.
There is much information to be found on this subject. It pays to look carefully at the tags of what appeals to you when shopping at your local nursery. A list of some of the more notable invasive species is included in this section. One of them, purple loosestrife, is a major nuisance in our wetlands and is available for purchase at many nurseries in the northeast.