Butterflies have survived for thousands of years on native plants. A good way to plan a butterfly garden is to use those native plants to attract local butterflies. Most of the native plants butterflies prefer are nectar-rich, with flower heads made up of numerous small flowers clustered together.
When you plan a butterfly garden, be sure to include plants for the butterflies' entire life cycle. Besides food plants, butterflies need host plants where they can lay their eggs. Host plants become the food source for the caterpillars that hatch. Many butterflies need specific plants for their caterpillars, and they will flock to gardens that offer them the right plants.
Joe-pye Weed, Eupatorium Purpureum
Joe-pye weed is a large plant, recommended by Glorious-Butterfly as an excellent plant for the back of a butterfly garden. It grows up to 8 feet tall and 4 feet wide. Clusters of dusty-pink flowers appear in the summer and bloom until fall. The flowers have a pleasing vanilla-like fragrance that perfumes the air.
The flowering period coincides with the most active period of two of the largest butterflies, swallowtails and monarchs. Joe-pye weed grows in average garden soil in full sun or partial shade. Native to the eastern and midwestern United States and southeastern Canada, joe-pye weed should be cut to the ground in the late fall or early spring. New growth emerges from the roots each year.
Yarrow is popular with herbalists, and its flowers are beloved by butterflies as well. Plant Safari describes yarrow as a plant with a clustered flowerhead. Yarrow plants are tough perennials that can form a thick mat of foliage, with the flowers held above on strong stems.
Yarrow flowers are of many colors, including red, yellow, white and pink, and they grow to about 18 inches tall. Yarrow tolerates hot, dry conditions. Keep the flowers trimmed off to promote fresh blooms for the late-summer butterflies.
Swamp Milkweed, Asclepias incarnata
Swamp milkweed is a common sight in ditches along rural roads. Cultivation information from ButterflyBushes states that swamp milkweed grows naturally with both pink and white flower clusters. Swamp milkweed is 30 to 40 inches tall at maturity. Plant it at the back or middle part of your garden, or in an out-of-the-way corner of the yard. It needs plenty of water.
Butterflies pollinate the flowers in the process of sipping the nectar. In the fall, unusual seedpods form, each one filled with hundreds of cottony tufted seeds that are spread by the wind.
Control the spread of milkweed by cutting off the spent flowerheads before the seedpods form. Many species of butterflies sip milkweed nectar, but for monarchs it is also a host plant. Swamp milkweed is deer-resistant. Many nurseries sell seeds or plants for different members of the Asclepias family.