
Common Fennel
Botanical Name:
Foeniculum vulgare
Class B Noxious Weed
General
- Escapes cultivation and quickly establishes dense infestations that crowd out native plants that are critical to wildlife habitats.
- May pose a threat to native grasslands.
Identification
- A large, aromatic, perennial herb.
- Can grow up to 6.7 feet tall (2 meters) and has a very large taproot.
- Foliage, stems, roots and seeds are hairless and all have a very strong licorice scent.
- Flowers are small and yellow and form an umbrella shaped cluster.
- Plants bloom from May to September.
- Leaves have an overall triangular shape and are many times divided into thin, featherlike leaflets and are dark green or bronze.
- Leaf stems (petioles) are swollen and fleshy and have a widened base.
- Stems are upright and branched.
- Seeds are about 0.15 inches (3.5 to 4 mm) long and have small ridges.
Habitat
- Found along roadsides, in pastures, prairies, streamsides, coastal bluffs as well as wetland areas..
Reproduction and Spread
- Reproduces from seed.
- Can also reproduce from pieces of the root crown.
Control
- Can be controlled using mechanical techniques as well as herbicides.
- Small infestations can be hand pulled but mature plants are difficult to remove because of the taproot.
- Above ground growth can be repeatedly cut prior to flowering to deplete below ground energy reserves. This technique may need to be down for several years to be successful.
- Cutting above ground growth when flowers are present may promote seed dispersal.
Chemical Control
2, 4-D amine
- Spot treatment: 0.25 to 0.5% solution
- Apply in spring to fully-grown leaves but prior to flowering.
- 2, 4-D is usually not able to fully control common fennel, so combining with other products is generally recommended. Retreatment will likely be necessary.
- Avoid drift to sensitive crops.
Glyphosate
- Rate: 2.8 lb ae/a
- Apply in spring to fully-grown leaves but prior to flowering.
- Adequate foliar coverage of fennel foliage is necessary. Add nonionic surfactant if not included in the formulation.
- Glyphosate is nonselective and injures or kills other vegetation in the treated area.
Triclopyr
- Broadcast treatment: 1 to 2 lb ae/a; spot treatment: 0.5 to 1% solution.
- Apply in spring to fully-grown leaves but prior to flowering.
- Do not drift onto sensitive crops.
- Do not contaminate water.