Fennel is a herbaceous perennial native to the shores of the Mediterranean but has naturalized in the US where it grows along roadsides, in pastures and in other open sites and is considered invasive in Washington and California. The plants grow 4- 8’ tall and have hollow stems bearing 16” long dissected yellow-green leaves with thread like segments. Twenty to fifty tiny yellow flowers appear in terminal compound umbels 2-6” wide in mid to late summer and give way to aromatic seeds heads. Leaves and seeds have an anise like flavor and aroma and are used in cooking. Fennel is also a food plant for the larvae of some swallowtail butterflies. USDA Hardiness Zones 4-9
The following natives are recommended as alternatives:
Heartleaf Alexanders (Zizia aptera)
Growing 1-3’ tall this herbaceous perennial has flat- topped umbels of tiny yellow flowers in late spring to early summer. The stem leaves are tripartite and toothed, while the basal leaves are heart-shaped. Native from New York to British Columbia, south to Georgia and Nevada where it grows in woods, thickets, glades, and prairies. USDA Hardiness Zones 3-8
Golden Alexanders (Zizia aurea)
This herbaceous perennial is native to open woods, floodplains, meadows, and prairies from Quebec and Saskatchewan, south to Florida and Texas. It grows 1.5’ to 3’ tall and has tiny yellow flowers in flat-topped umbels in late spring. The leaves are compound biternate with toothed leaflets. USDA Hardiness Zones 3-8