Some customers ask about purchasing seeds of perennial plants to sow them where they are to grow, directly on the ground. While this technique works in some situations (after all, that's how nature does it) we feel that in most cases, perennial wildflowers, grasses, trees and shrubs should be sown in flats or in 4" pots first, where conditions of moisture, temperature, and weeds are more easily controlled. This is the best way to optimize your chances of success with your purchased seed. Nature, unlike us, can afford to be profligate with seed distribution. Annuals, with their quick germination and fast early growth, are appropriately sown directly in the ground.
That said, there are always exceptions, such as gumplant (Grindelia stricta), or peppermint candy flower (Claytonia sibirica), which reseed so vigorously that they can be safely broadcast sown. Each species' listing will tell you this and much more information. One packet contains enough seed for 20 to 30 plants.