How to attract butterflies to the garden:
1. Plant Gregg's Mistflower. The mistflower I have in the back (i.e. full sun) is blooming right now. The mistflower in the front (i.e. dappled sun) isn't blooming, nor will it until the fall.
2. Plant Butterflyweed. Oh my God. This plant is ALWAYS COVERED in aphids. But! Aphids eventually bring lady bugs and lacewings. And, of course, it is the host plant for the monarchs, and they need as much help as they can get.
3. Plant Dill, Parsley, or Fennel (though I've found that Dill works the best). When it blooms, it brings the bees, and until it does, it will host all those swallowtail caterpillars. And eventually, you'll find a few of these on other plants (the swallowtails sure like to travel to a different location to pupate).