The answer to 'why is my garden invasive plants' is that your garden likely has an overgrowth of non-native, aggressive plant species that are outcompeting your desired plants. Invasive plants can spread rapidly, crowd out native vegetation, and be difficult to control. Common causes include improper plant selection, lack of maintenance, and introduction of invasive species through gardening materials or nearby areas.
Symptoms of an invasive plant problem include rapid growth, spreading into areas they weren't planted, and a decline in the health and diversity of your desired plants. Solutions include identifying and removing the invasive plants, using native or non-invasive species, and implementing an ongoing maintenance plan. For severe infestations or difficult-to-control plants, it's best to call in a professional landscaper or horticulturist.