Butterflies are creatures of warmth and sun, and most of the flowers they are attracted to are sun-lovers too.
Generally speaking, it's better to plant several plants together to create a mass of color than to have single plants scattered around.
Plan your garden to support the whole butterfly life cycle, not just the adults that nectar at flowers. Butterflies will lay eggs only on the plants that will nourish their caterpillars. This is species-specific. For example, monarchs use milkweed for their caterpillars. Eastern Black Swallowtails use dill, fennel, parsley, and other members of that plant family. Find out what butterflies you can expect to see in your area and what plants they will use as larval food. Plant them, and watch for caterpillars!
One thing to beware of when buying plants for caterpillars is that many commercial nurseries have applied pesticides to their plants, either by spraying them or through systemic application, which means they can't be washed off. Caterpillars that eat poisoned plants will die. You can pretty much expect that plants purchased at the garden department of your local mega-store will fall in this category. Try to find a local nursery that is knowledgeable about butterflies and ASK if they have put pesticides on their plants. Best bet: nurseries with plants that have caterpillars thriving on them!
Another thing to consider is planting with native plants. Native habitats are constantly being destroyed by new development, and butterfly populations suffer as a result of this. A good local nursery that carries native plants is a great place for more information about this. Information about native plant nurseries in the Carolinas is available on the main Gardening page of this website.
Also: beware of fancy hybrids. They look beautiful, but very often the breeding process that produces the lovely blossoms also reduces or eliminates the quantity of nectar that is produced. If there is no nectar, butterflies have no use for the flowers.
A starting list of nectar plants for your yard & garden might include:
A starting list of Larval Food plants for caterpillars might include the following. Note: this list applies in the Southeast United States and is very general. It may or may not apply where you live, and does not apply universally even in the Southeast.
There are many resources for more information about butterfly gardening. Check other sections in the gardening area of this web site, the Links & Resources page, your local library, your local butterfly society, native plant nurseries, etc. Happy Gardening!!!!