It's ideal to have host plants and nectar plants growing in your garden if your goal is to attract butterflies. Selecting what to plant varies enormously based on what butterfly species you wish to attract.
Butterflies will roam in search of food and egg-laying sites for many miles—even hundreds to thousands—of miles. Butterflies lay their eggs on host plants that the emerging caterpillars will eat. Different species of butterflies prefer different types of plants to lay their eggs on.
Milkweed and Monarch Butterflies
The monarch butterfly however is very specific and only lays her eggs on species of Asclepias - commonly known as milkweed.
Each fall, millions of monarch butterflies migrate from the United States and Canada to overwintering areas in Mexico and California and make the return flight in spring. Threats, including loss of milkweed habitat, are having a devastating impact on monarch populations. By planting milkweed you can help save the monarch butterfly.