Bee balm (Monarda) is a member of the mint family and spreads by runners (underground stems) and seed. If you are growing this in Canada or the United States, it can be an aggressive grower. This is a good example of a native plant that is beneficial to wildlife yet problematic for some growers. In my experience (southwestern Ontario, Canada), it is not, however, truly invasive like some mints where the roots are nearly impossible to remove. Bee balm roots tend to be shallower and easy to pull. If it was like mint, I would only grow it containers. I let it spread in my garden and pull some out every few years to leave room for other plants. It is always good to check with your local university extension office or conservation group to research any plants you want to grow and be sure you are making environmentally-beneficial choices for your region.