As a comment about Sweet Indian Plantain (Hasteola suaveolens)
This plant is native to many states north-east of the Missouri River, though in some states that range is very limited. It is listed as Endangered in Connecticut, Maryland, Minnesota, and New York; Threatened in Iowa and Tennessee; Historical (presumed extinct) in Rhode Island. In Minnesota, for one example, there are only 15 known occurrences, yet according to their DNR "No conservation efforts have been undertaken specifically on behalf of this species." Threats to this plant are the damming of rivers, draining and filling of wetlands, browsing by deer, invading noxious weeds, and development.
This risk of extinction is why I chose the plant when I saw it on special where I order many natives. Because the county plants natives in our ditches, I do not worry if this spreads outside my property. That risk seems small, though, because it is not aggressive, and it may require more water than the amount that flows down the ditches.
Standing water is good for this plant. Mine is planted in a low spot, which does help when there are heavy rains and field run off, but it is not quite enough. I have to give ours a dose of collected rain water now and again as they will look droopy when they begin to dry out.
The flowers are not all that impressive, but the leaf size and the possible height of up to 7-8 feet are! This will work in landscaping conditions, but it does need room for its large size and plenty of watering. Because of its conservation status in different areas, it may be illegal to take seeds or to dig up any that are growing in the wild, so make sure to buy from a company that sells from their own stock.
Some plants are made to be resilient and can come back after abuse. This is one of them! And it is the reason I now have to use bright orange flags to mark my plants. Someone who didn't remember this patch mowed it down to lawn height. Other than a few scraggly mature leaves, nothing remained. But within a handful of days and with plenty of water, they bounced back. They are now rewarding me with some flowers.
Even though it is named Plantain, it is not closely related to the weedy non-native Plantain (Plantago major).