The problem with butterfly garden design these days is that they tend to be butterfly nightclubs. Basically, these gardens are for adults. Take the ubiquitous butterfly bush (Buddlia davidii) for example. You may find it covered with butterflies, but where are the caterpillars? Besides the fact that butterfly bush is now on many invasive species lists, it provides virtually no value to butterflies during their larval stage, i.e. childhood. It is basically a place where grownup butterflies go for a drink.
So for a garden that addresses the needs of butterflies throughout their lives, what should you plant? Every good parent knows that a healthy childhood is critical to their offspring, including butterflies. While humans try to provide a stimulating, caring, and healthy home or daycare facility for their children, butterflies look for rich gardens with the right plant material on which to lay their eggs.
Although this makes designing a butterfly garden more complicated than simply planting flowers, there are some valuable resources available to you. My favorite is called Caterpillars of Eastern North America by David L. Wagner.
It not only helps you identify the caterpillars (the larval stage of the butterfly) in your garden, but it shows you pictures of the butterflies that they become, and it also lists the plants that the caterpillars eat. It even has a Foodplant Index in the back which lists plants and then references the caterpillars that eat that particular plant.
For example, one day you find a caterpillar on your parsley and you don’t know what it is. Will it become a beautiful butterfly, or is it a pest in your herb garden? Using the Foodplant Index, you can look up parsley and discover that the caterpillar is a black swallowtail which also eats anything in the carrot family. If you happen to have Queen Ann’s Lace around, you can pick the caterpillar off of your parsley and move it to the Queen Ann’s Lace, saving your parsley and keeping the caterpillar happy in the process. If you don’t have Queen Ann’s Lace, you may decide to sacrifice your plant for the butterfly and pick up some parsley at the store.
Another way to use this book, is that you can reference it to install food plants for specific butterflies. Let’s say you want to attract Tiger Swallowtails to you property. If you look up the caterpillar you will see that it eats sweetbay magnolia (Magnolia virginiana), tulip poplar (Liriodendron tulipifera) and cherries (Prunus sp). You can then use this information to plant a sweetbay magnolia on your property and increase the chances of attracting Tiger Swallowtails.
You may even find this approach changes the way you garden. For instance, you may have been fighting violets in your garden beds for years, but upon investigation you find that violets are the only food source for one of our most beautiful butterflies, the Great Spangled Fritillary. Now you see violets as an asset, and decide to leave at least some in your beds for the butterflies resulting in less work for you and more food for the caterpillars. Now that is a win-win!
The point of all of this is, if you want a butterfly garden on your property, think more nursery than nightclub. Your whole property should be full of diverse plantings to feed a variety of caterpillars. Provide a healthy childhood atmosphere for the butterflies, and when they grow up they can hang out at the clubs.