I grow plantain leaf in my garden, I've always used it to stop diarrhea, it works well for children in this way as well. It grows very easily and has self seeded and is almost a weed in my garden now. Chickens also like it. Its great to add to anything, stirfrys, salads, even on a sandwich.
For diarrhea or bowel problems I have found it works best if eaten fresh and raw, not cooked.