When you are planning a butterfly garden, one of the things you do is research which plants will attract them. You want to make sure that you have both host plants and nectar plants so that the caterpillar and the adult butterfly have the food that they need to sustain them. The problem is that some plants that are recommended by garden centers, on the internet and in reputable gardening books are not quite what they seem. Such is the case with the butterfly bush (Buddleja/Buddleia davii).
The butterfly bush species from Asia and Central America are popular ornamental plants widely used to attract butterflies. There are more than 100 species of Buddleja worldwide and additional cultivars are being developed. Buddleja species are currently found throughout the eastern, southern and western states here in the United States. They are attractive and colorful and they do attract butterflies.
But there are two big problems with these plants, according to Doug Tallamy, PhD, professor and chair of the department of entomology and wildlife ecology at the University of Delaware in Newark. Because they are not native to our region these plants are not equipped to feed the beneficial insects and birds that are common in this area. This in turn disrupts the entire reproduction process. The butterflies that we want to bring into our gardens don’t get the food they require to reach adulthood and in turn to produce future generations for us to enjoy.
The first issue is that the butterfly bush, which has been placed on a number of government and university invasive species lists, has the ability to spread easily and outcompete native plants. Because they are non-native, these plants have virtually no natural predators here, so they infest areas and crowd out the natives which butterflies, other species of insects and birds rely on to reproduce.
The butterfly bush can escape from plantings and become invasive in a variety of natural habitats such as coastal forest edges, roadsides, abandoned railroads, rural dumps, stream and river banks and some disturbed habitats.
In Oregon the sale of this plant has been banned because it has become so invasive. Oregon’s wet climate is a perfect environment for the Buddleia. In Cape May, N.J. it is blocking out fragile dune vegetation on the beaches. In our own Pocono Mountain area in PA it is taking over stream banks for miles.
The butterfly bush is considered invasive in over 25 North American states, including Massachusetts, Connecticut and Rhode Island. It is considered prolifically invasive in Zones 6 and 7 (Mid-Atlantic States such as PA and VA) as well as the Northwest. In New Jersey its use has been prohibited in public lands.
Why is it so invasive? One reason is that they so easily go to seed. Unless all flower heads are deadheaded or clipped off in the fall lots of ‘volunteer’ bushes appear when spring arrives. If clippings are left on the ground, they easily take root and generate more plants. If clippings are dumped instead of being ground up, composted or burned they can take over an area. Clippings that have been dumped along roadsides or along streams create even more bushes because this is their preferred habitat.
Tallamy also raises a second serious problem with the Buddleja species. While they may provide nectar for the adult butterfly, this is not a host plant for caterpillars. According to Tallamy, not a single species of native caterpillar will feed on Buddleia. And, without the caterpillar there is no butterfly. Thus, without an adequate supply of native host plants, butterflies will continue to decline.
If you do a survey online of this plant, you will find many gardeners that are quite upset about the warnings and the limitations that are being placed on a plant they love. There are now cultivars of seedless or low seed varieties of the Buddleia being developed. But if you look at the facts and want to do what is best for conserving our butterfly population, you will look to other more appropriate natives plants. One such group of plants is the milkweed (Asclepias). Tallamy recommends species that can be planted together: the butterfly weed (Asclepias tuberosa), common milk weed (Asclepias syriaca) and swamp milk weed (Asclepias incarnata). Not only will you have wonderful flowers from June into September, you will also have the butterflies that are supported by this species.
Monarch Caterpillar on the Butterfly Weed.
Swamp Milkweed with Skipper
AUTHOR’S NOTE: In my opinion, Tallamy’s book is a must read for anyone interested in what they can do to counter the effects of over development on our environment. He offers many solutions on how to sustain the wildlife we value in our environment.
Bringing Nature Home, How Native Plants Sustain Wildlife in Our Gardens by Douglas W. Tallamy (Timber Press, Inc. 2007)
Click on any of these links for more information including a database of invasive plants for our region:
Mid-Atlantic Exotic Pest Plant Council, Inc.
National Invasive Species Information Center,
Plant Invaders of Mid-Atlantic Natural Areas
USDA – NRCS PLANTS Database Rodale News Ecosystem Gardening Oregon State University Extension
Images: Located on Wikimedia
Swamp Milkweed Photo by and (c)2009 Derek Ramsey on http://commons.wikimedia.org