Q: I’m considering planting Mexican petunia by my mailbox. However, I am reading where it can be very invasive and do not want it to overrun the azalea and hostas I have in there now. What are your thoughts?

A: In my experience, the tall form of Mexican petunia, Ruellia brittoniana, will certainly spread to fill a given space. If nearby plants are short, this ruellia will shade them.

On one hand, there are at least three varieties of ruellia that are dwarf forms: ‘Katie’, ‘Chi Chi’ and ‘Bonita’. All yield the non-stop flowering of the tall form but are much less aggressive to neighbors.

On the other other hand, Florida has named ruellia as an invasive plant with potential to adversely affect native habitat. My advice is to use caution with this plant and remove unwanted seedlings as they occur.

see Natural Area Weeds

Ruellia tolerates wet spots very well. I have a clump growing in a pot submerged at the edge of a shallow pond.