Some one told me that butterflies are not really equipped to access the nectar from a butterfly bush. Is this true? Can you explain the impact of this plant on the environment to have it considered invasive?
Butterflies can access the nectar from butterfly blooms, however, the problem you often hear about is that their caterpillar or larval stage cannot eat the plant's leaves. And, of course, no caterpillars = no butterflies. It is vitally important to grow plants whose foliage feed the larval stages of butterflies and moths. Our instinct is to be alarmed by insect foliage feeding, so this is a big attitude adjustment for most homeowners!
The other big problem with butterfly bush is that the plant itself sets tremendous loads of seed, and it has become invasive in some areas and is on some invasive species lists. The more butterfly bushes are planted, the more viable the seeds can be. So, we encourage homeowners to plant a diversity of plants that butterflies use in all their life stages.
If they want the butterfly magnet provided by butterfly bushes, there are some new varieties of butterfly bushes that set extremely small amounts of seed compared to most (but are not completely sterile). This includes the Flutterfy and the Lo and Behold series, as well as B davidii 'Asian Moon', 'Miss Molly', and 'Miss Ruby.'