Black Swallowtails and Their Host Plants

Herbs do best in Florida in the cooler seasons, and they positively thrive in late winter and spring. Humans love herbs for cooking, of course, but here at BioWorks we grow several types of herbs just for Eastern Black Swallowtails (Papilio polyxenes). Eastern Blacks host on plants in the Parsley family (Apiaceae), along with Common Rue (Ruta graveolens). Although this time of year you may not see many Eastern Blacks flying, now is the time to establish a healthy herb garden to support them when they’re around. Most herbs are easy to grow from seed, and if you start now, you’ll be in good shape when the Eastern Blacks arrive later in the spring.

Here at BioWorks, we grow parsley, dill, and fennel for our caterpillars to enjoy. Curly parsley especially has become popular in recent years for ornamental growth as well as herb gardens – during last year’s Epcot Flower and & Garden Festival, enormous planters of curly parsley made great impact with their fresh green color and scent. Flat Italian parsley works just as well for the caterpillars though, so there’s no need to be picky on their account.
Dill and Fennel are also great hosts. We’ve had a great deal of luck with Fennel especially – it tends to re-seed and even re-grow from the base far better than dill or parsley. It makes a nice ornamental plant as well, with its tall feathery growth. Plant it at the back of a garden for a backdrop of delicate green, or in a sensory garden to enjoy the licorice smell.
We also use Common Rue as a host plant for Eastern Black caterpillars. Rue has its benefits and its drawbacks – it grows fairly readily and is used by both Eastern Blacks and Giant Swallowtails (Papilio cresphontes). However, it has a fairly unpleasant smell and can cause skin rashes for some. Grow it at your own risk!
Whichever herbs you choose for your Eastern Blacks, here are some growing tips for Central Florida, based on our own trial and error:

• Though herbs are generally said to do best in sunny spots, ours seem to do best in partial shade. This allows them to thrive a few extra weeks when the hot part of summer arrives.
• Herbs do need regular water. In dry times of the year, like winter and spring, you’ll need to provide some supplemental water to help them do their best.
• When herbs begin to produce seed heads (called “bolting”), you should snip these off to encourage the plant to continue leaf production rather than put all their energy into seed production. If you want to collect seed, allow one or two seed heads to develop.

NOTE: We know that some folks may actually consider Eastern Black Swallowtail caterpillars to be pests, rather than welcome visitors. If you’re having trouble with them, consider setting aside a few plants just for the caterpillars. You can move any new caterpillars to these plants when you find them, saving the rest of the plants for yourself.