Had to look that one up, that's a really good example of the sort of unexpected complexities that can come up (many years later in this case).

For others (like myself) who haven't seen it before: https://academic.oup.com/bioscience/article/57/11/956/234351

> Consequently, individual cultivars themselves are not invasive, but the combination of cultivars within an area creates a situation in which invasive plants can be produced.