The answer to 'why is my flower bed invasive plants' is that your flower bed has become overrun with unwanted, aggressive plants that are spreading and taking over the desired flowers. This is a common problem that can happen due to factors like improper plant selection, lack of maintenance, or environmental conditions that favor the invasive species.
Some common symptoms of an invasive plant problem in a flower bed include rapid growth, crowding out of other plants, and the presence of aggressive, spreading roots or runners. The best solution depends on the specific invasive plants, but typically involves a combination of manual removal, applying herbicides, and taking steps to prevent future invasions.