Poncirus trifoliata (Bitter/Sour/Hardy Orange)
This well-thorned member of the Rutaceae family is often used as rootstock for orange trees, to which it appears closely related. However, the fruits are extremely bitter and are reported to contain a somewhat toxic saponic glycoside as well as an oil that can be irritating.
Despite this, I suspect it may have some healing qualities similar to an unrelated plant that also has saponic glycosides in it, as well as a bitter principle, which, I read, grows in South America. The Zulus and others use that plant for various purposes.
I would like to try to grow Poncirus. The seeds are said to be most viable when first taken from the fruit. Does anyone know of a nursery that sells self-rooted plants or the whole ripe fruit?
Here is a link that might be useful: Poncirus trifoliata