My husband and I were lucky enough to catch the Wings of Fancy live butterfly exhibit at Brookside Gardens on the weekend before it closed. If you missed it, check out the Smithsonian Natural History Museum's live butterfly pavilion, which is open year-round. At Brookside, they had an informational pamphlet entitled "Gardening for Caterpillars & Butterflies." Included in the pamphlet was the website for the North American Butterfly Association (NABA), an organization that offers butterfly garden certification. Since my garden meets (and exceeds) the requirements, I was inspired to register my garden with the program.
Two Black Swallowtail caterpillars eating parsley in my garden
The butterfly garden certification requirements are as follows:
At least three different native plants that serve as food sources for butterfly caterpillars
At least three different native plants that serve as nectar sources for adult butterflies
A commitment to not use pesticides of any kind
You have to do a little bit of homework to determine which butterfly garden plants will work in your garden. NABA offers some guidance with their recommended list for Central Maryland (close enough for DC). For additional caterpillar food sources, I used the Butterflies and Moths of North America list, restricting the suggestions to DC natives less than 6-feet tall, as I just don't have the space for trees and larger shrubs. For additional nectar sources, I also referred to the Xerces Society's Pollinator Plants of the Mid-Atlantic list.
In my backyard garden, I have the following caterpillar food sources:
The flowering plants in the above list serve dual purposes of being caterpillar food and nectar sources for adults. The native grasses are also resources for birds, providing nesting materials in the spring and edible seeds in the fall.
Native plants that serve as nectar sources in my backyard garden include:
My front yard garden has only two caterpillar food sources: Ceanothus americanus (New Jersey tea) for Spring Azure and Summer Azure as well as Fragaria virginiana (wild Virginia strawberry) for Gray Hairstreak. There are several nectar sources in my herb beds, all belonging to the mint family: mountain mint, beebalm, anise hyssop, holy basil, lemon balm, oregano, thyme, and winter savory.
As for the third requirement of no pesticides, I've written previously that I used to spray Btk on Brassica crops as a treatment against cabbage worms. I've sinced learned that while it's considered organic and bee-safe, Btk doesn't just kill pesky cabbage worms but all caterpillars, and so it has no place in a certified butterfly habitat. Therefore, I no longer use Btk or any pesticides, synthetic or organic. I mostly leave pest control to birds and predatory insects, though I will occasionally hand-pick cabbage worms if I find significant damage.
I submitted the application for certification on NABA's website and paid $40 ($15 for the butterfly garden certificate, plus $25 for a weather-proof sign). My sign arrived last week and I proudly hung it on my backyard garden gate.
I hope that I can inspire neighbors, passersby, and readers of this blog to include more plants for butterflies in their gardens.