If you want to attract butterflies into your garden you need to grow the appropriate plants. These will be of two sorts. One group of colorful flowers to attract the adult butterflies, and you also need to provide other plants to feed the caterpillars that will eventually turn into the next generation of butterflies. This is explained in greater detail by Teresa Gallion in her article which I found on The Master Gardeners website.
Starting is easy, especially if you already have a flowerbed. Just remember for a butterfly garden you have two goals: the first is to attract adult butterflies to come into your garden and the second is to ensure further generations of butterflies by providing a place for eggs and caterpillars.
Look for a sunny site. Avoid very windy areas like hilltops. Flight is less work in sun and calm air. Don’t forget, they’re looking for food. Location is everything. You want to be able to grow the nectar-producing flowers butterflies need. You also want the butterflies to be able to spot your garden; so don’t hide it from them.
Plant bold masses of bright flowers. That will bring then in. To keep them feeding take a look at how they feed. Butterflies have a proboscis they use for eating – it’s pretty much a curled up straw they can extend into flowers to drink nectar. They’ll stay and feed longer where there are lots of flowers with accessible nectar.
The kinds of flowers you’ll want to plant will provide the butterfly a place to land and be able to reach the nectar with his proboscis. There are many possibilities. Ask at your garden center. Many plants are being labeled “for butterflies”. As a rule of thumb, think of the butterfly bush (Buddleia sp.). The blooms are actually small bunches of tiny flowers. Butterflies can land on the bloom and spend a long time drinking without spending a lot of energy flying around. Some others that meet this standard are the native Joe Pye weed (Eupatorium maculatum), the golden rods (Solidago spp.), butterfly weed (Asclepias tuberosa), and Verbena bonariensis.
See more at The Master Gardeners