Foeniculum

A small group of perennials, with very fine, dissected leaves, scented and umbels of yellow flowers, very popular with small insects. F. vulgare is herb fennel, grown for leaves and seeds. F. vulgare var. azoricum, the bulb fennel.

Probably grown in Britain since Roman times as a culinary herb, fennel is now established throughout the lowlands, especially by the coast, on brownfield sites and road-verges. As with all umbellifers, the heads of numerous small flowers provide a huge resource of nectar and pollen for a wide range of insects from tiny pollen-beetles to wasps and especially hoverflies. The seeds will also be taken by seed-eating finches, while the leaves are a food-plant of the continental form of the huge swallowtail butterfly. This form is being seen increasingly in the south of the country, and indeed has established itself at least temporarily in places, so you could just be lucky!