Growing plants that attract butterflies is a sure-fire way of engaging children in the garden, and it invites discoveries about pollination, insect life cycles, and the interdependence of insects and plants. The first step is understanding what makes butterflies tick at different stages of their life cycle.
The cycle begins when adult butterflies lay eggs on a "host" plant. Some butterflies will only lay their eggs on a single type of plant, such as monarchs preference for milkweed. Others have several choices. In about five to ten days, the egg hatches and the tiny caterpillar begins eating the host plant, shedding its skin four to six times as it grows.
After two to four weeks, the full grown larva, or caterpillar, attaches itself to a twig or other object and transforms into a pupa. The body changes during this inactive stage, and ten to fifteen days later the adult butterfly emerges. This process, called metamorphosis, means "change of form."
Adult butterflies feed on nectar from flowers (and in doing so, inadvertently pollinate some) while the larvae feed mostly on the foliage of plants. Ideally, a butterfly garden should contain or be located near a range of plants that will feed the butterfly at both stages.
You need only a small garden bed to create an inviting oasis for butterflies. Both butterflies and plants like sun so plan your garden with a southern exposure or in a site that gets at least six hours of sun each day. A site sheltere plants from blowing over, and allow your butterflies to feed, mate, and lay eggs in relative tranquility.
* Nectar flowers provide a source of food for adult butterflies. Butterflies are attracted to brightly colored, sweet-smelling flowers that allow them easy access. Composite daisy-like flowers are favorites. Some of the preferred, easy-to-grow nectar plants are: aster, black-eyed Susan, butterfly bush, butterfly weed, cosmos, goldenrod, lantana, lavender, liatris, marigold, purple coneflower, and zinnia. Butterflies are attracted to masses of color and fragrance, so try to plant groups of flowers instead of single plants. If space is limited, however, even window boxes can catch butterflies' attention.
* Host plants are those preferred by butterfly larvae (caterpillars). They are usually wildflowers, shrubs, and trees native to the area. Some species will lay eggs on only one type of host plant (e.g., monarch caterpillars will only eat milkweed), while others are less particular. Some of the primary plants for butterfly larvae include: aspen, alfalfa, clover, nettle, pearly everlasting, milkweed, grasses, hackberry, parsley, vetch, and willow. Although the caterpillars of some butterflies, like the cabbage white, are considered vegetable garden pests, you should never use pesticides--even biological ones--in a butterfly garden or you'll destroy your intended guests.
* Puddles or other shallow water sources are important, primarily for male butterflies, more as a source of salt and amino acids than as a water source. If you have no naturally occurring puddles, try sinking a shallow container filled with moist sand, dirt, and/or stones into the ground. Keep it moist and watch for large congregations of butterflies.
* Dark stones in your garden can provide a warm spot where adult butterflies can bask in the sun and warm their bodies for flying.