I don't think there are any ruellia that spread with tubers like bindweed (just an FYI), but they certainly do from seed. Seeds are ejected from the seed pods, usually at just the tiniest hint of turning brown. So if you can't remove the plant, cut off the seed pods well before they ripen. And be sure to discard in the garbage any remnant pods and not leave them lay. Even green seed might be old enough to finish ripening off the stem. Seedlings are difficult to pull, as they produce a deep root system from the get-go.
