Did you know that the botanic community is split on the issue of butterflies? We didn't either, until we visited the UC Berkeley Botanical Gardens on a field trip.
We were there for a screening of a documentary about the life cycle of butterflies called "In the Company of Wild Butterflies." The film was presented by Sally Levinson, a docent for the gardens who's also known as "The Caterpillar Lady."
Different kinds of butterflies need specific kinds of chemicals to survive, and they find them in specific kinds of plants. Swallowtail butterflies , for example, thrive on yampah. But there isn't much yampah around anymore, because marshes have been drained and houses have been built and development has wiped out its natural habitat.
The swallowtail found a replacement for yampah in fennel, but therein lies the problem. Fennel is a non-native, invasive weed, the kind of plant botanists are not at all fond of. So while the butterfly people would love it if you let that fennel stay in your garden, the botanists know that it threatens native plants.
What to do? Andy Liu, a landscape engineer who also volunteers at the botanic gardens, says that you can control fennel without eliminating it entirely. You just have to make sure that it doesn't spread. So if you'd like more butterflies in your garden, let a few weeds join the party.
Bring your macro lens with you. And go for details; zoom in on a little piece of the action for more drama.