Butterfly host plants serve two purposes:
Be prepared for serious munching on these butterfly plants.
Host plants are key to your butterfly garden. They create a complete butterfly habitat. If you only have blooming flowers the occasional adult butterfly will stop by for nectar then move on. If there are no host plants, there is no consideration for the female to lay her eggs.
You can locate butterfly hosts in low visible areas and outer parameters
of your property. If you put plants closer to your home, alternate host plants and flowering perennials with annuals. Do this for two reasons:
A butterfly host plant can be a plant, tree, bush - not necessarily
flowering. Many plants serve as a host to most types of butterflies. There are a
few species where only one or two butterfly plants will sustain them for life.
This video discusses host plants for planting zones 6 -7, Oklahoma. Any location in North America can benefit watching as many gardeners are familiar with all plants mentioned. Watch also the neat trick to expose the butterfly's osmeterium, a defense organ on Swallowtail butterflies.
Should you live in a humid environment, this is good for butterflies. Caterpillars are able to emerge from their eggs more easily and the tender leaves from the host plants are easier to nibble.
If your environment is not so humid it is a good idea to spray plants with a garden hose on extremely hot days.