Can you graft a thorn apple tree to a sweet apple tree?

Grafting a thorn Apple tree (Datura) to a sweet Apple tree (Malus domestica) is generally not successful because they belong to different genera and families. Grafting typically works best within the same species or closely related species. While some grafting techniques can sometimes yield hybrid fruits, the genetic differences between these two plants make successful grafting unlikely. If you're interested in grafting, it's best to use compatible Apple varieties or related species.