Butterfly bushes are considered bad primarily because they are invasive plants that spread aggressively, displacing native plants and disrupting local ecosystems. They produce a huge number of seeds that spread by wind, water, and animals, allowing them to quickly colonize new areas and create monocultures that choke out native species. This reduces biodiversity and harms wildlife that depend on native plants for food and habitat, including butterflies. Although butterfly bushes produce abundant nectar, which attracts adult butterflies, the nectar is high in sugar but low in other nutrients, providing only a quick energy boost rather than balanced nutrition. More importantly, butterfly bushes do not serve as host plants for butterfly larvae; native caterpillars cannot feed on their leaves, so butterflies cannot reproduce successfully if native host plants are crowded out by butterfly bushes. This irony means that butterfly bushes can harm butterfly populations by distracting adult butterflies from laying eggs on appropriate native plants and by eliminating the habitat needed for their caterpillars to survive. Additionally, butterfly bushes have an extensive and aggressive root system that can damage masonry and walls by growing through cracks, potentially causing structural damage. In summary, butterfly bushes are bad because they are invasive, reduce native plant biodiversity, disrupt ecosystems, harm butterfly life cycles, and can damage structures with their roots.
