Real meadows are generally a mix of annual. biennial and perennials. I know that here in Texas, unless they are hand seeded, a lot of the necessary plants won't grow on their own unless there has been a sufficiently large grass fire to trigger germination. Since we're not normally allowed to go around lighting fires, we end up buying seeds and seeding them.
Look and see if your state has an Open Prairie Management program. Even if you don't end up converting to prairie, they can still advise you on what will grow best in your area. In some cases, its even possible to a break on the property taxes. They can even advise you on the best prep methods for your area and how long it will take. If you're outside North America, there
should still be some sort of an agency with that information.