(Fennel) If you are looking to add the interest of butterflies to your garden, consider planting Fennel in your garden. Standing up to 6 feet tall, Fennel likes to be planted in full sun locations with moist, well-drained soil. Hardy in zones 4-9. this is a host plant for Anise Swallowtail and Black Swallowtail butterflies. This easy to grow herb readily reseeds. Fennel is an herb that can also be used in cooking. Just be sure to check for the butterfly larvae before taking a bite.