The answer to 'why is my hedge invasive plants' is that your hedge may have become overrun with invasive plant species. Invasive plants are non-native species that can quickly spread and crowd out your desired hedge plants, causing it to become unruly and difficult to maintain. Common signs of an invasive hedge include rapid growth, dense foliage, and the presence of aggressive spreading roots or seedlings.
To address an invasive hedge, you'll need to identify and remove the problematic plants. This may require digging out the roots, applying herbicides, or regularly pruning back the invasive growth. In severe cases, you may need to completely remove and replace the hedge. To prevent future issues, consider planting native, non-invasive hedge species that are better suited to your local environment.