Weed Potential 
As a weed Fennel is wide spread appearing on disturbed or degraded land including grasslands, open woodlands, along water courses and drainage lines or along roadsides. The plant first forms a single or multiple stems during spring and dies off in autumn. 

In the second year flowers are produced and seeds are released from summer to autumn. It grows in full sun to semi shade preferring moist soils but will tolerate drier conditions once established. 

Dense infestations inhibit the regrowth of low growing or upper-story indigenous flora. The seed is dispersed by water, soil, machinery and wind. It may also be spread during physical removal of an infestation. 

Control methods include physically digging out small clumps and bagging of seed heads. Stems may be slashed during late spring to inhibit seed production and sprayed or painted with a non-selective herbicide. Follow up spraying will be required or hand removal of young plants.