Summary:A fine leaved perennial shrub with erect, many branched stems reaching 2 m or more tall and a strong aniseed-like smell. The yellow-green flowers are in compound umbrellas at the top of the plant from late winter to summer.
Leaves:Alternate, form a basal rosette, aromatic, aniseed scent.
Stems:Erect, faintly striped, solid with white spongy pith, stout, aromatic, aniseed scent, tufted or branched and with several stems emerging from each crown, Up to 2500 mm tall. Jointed at the nodes. Hairless. Often with a waxy bloom.
Flower head:Umbels in a terminal corymbose panicle. Many flowers produced together in the umbrella-like compound umbels on a stalk (peduncle) with 10-40 spreading rays that are 10-50 mm long and end in a small umbrella like structure with 10-30 flowers. No bracts or ray bracts.
Flowers:Green-yellow and 2-6 mm in diameter and bisexual. On different length, ridged, short stalks (pedicels).
Fruit:Grey to yellow brown, aromatic, short, oblong, cylindrical, 3-6 mm long x 1-2 mm wide, with 2 flattened, arched, egg shaped fruitlets with 5 thick ribs, a pointed tip and a rounded base. Hairless. Axis separating fruits is persistent, 2 lobed with a broad seam and 2 oil channels, (6 in total with 1 in each furrow).
Key Characters:Liquorice like (aniseed) odour.
Reproduction:By seed and from the crown.
Flowering times:Late Spring to summer in western NSW.
Seed Biology and Germination:Germinates at any time of the year with a flush in autumn and spring.
Hybrids:Cultivated varieties exist. Variety dulce or Florence Fennel and azoricum is used for food, variety vulgare for medicine.
Allelopathy:Tomatoes and beans don't grow in association with Fennel.
Population Dynamics and Dispersal:Spread by vehicles, machinery, flowing water, on animal coats, wool clothing, hides and as a contaminant of agricultural produce and land fill.
Origin and History:Southern Europe and Western Asia.
Distribution:ACT, NSW, QLD, SA, TAS, VIC, WA.
Habitats:Prefers open unshaded areas.
Climate:Humid temperate with medium to high rainfall.
Soil:Most abundant on limestone soils and calcareous wetlands.
Detrimental:Weed of roadsides, railways, stream banks, alluvial flats, irrigation channels, gardens, refuse sites and disturbed areas, particularly in suburban areas.
Toxicity:Death of sheep and cattle have occurred after eating residues from distillation plants. Stubbles do not appear to be toxic and it is rarely if ever a problem in field situations.
Legislation:Noxious weed of Vic. Secondary weed of Tas.
Management and Control:Thresholds:
Eradication strategies:Manually remove isolated plants. A hand mattock that cuts the root below the surface is often used.
Herbicide resistance:Biological Control:
Plants of similar appearance:Aniseed plant (Pimpinella anisum) has a similar aroma and is in the same family.
References:Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P75. Photos.