Montpellier broom (Genista monspessulana)

High Risk Weed for Kangaroo Island

Montpellier broom is an Alert weed for Kangaroo Island. Notify the Kangaroo Island Landscape Board. Early detection and control are the best way to prevent the next widespread weed. 

It is a declared plant for South Australia. 

THE SITUATION AND WHAT TO DO

Montpellier broom (also known as Cape broom) is a perennial shrub native to the Mediterranean region of southern Europe and North Africa. It was introduced to Australia in the 1800s as an ornamental garden and hedging plant, from where it escaped cultivation and spread into natural and agricultural landscapes.

In South Australia it is a significant environmental pest plant, particularly in the Mount Lofty Ranges, where it invades woodlands, forests, roadsides and disturbed areas. It forms dense thickets that exclude other vegetation and persist for many years due to viable seed a large soil seed bank.

The plant spreads mainly by seed as seed pods burst open and eject seeds several metres from the plant, while further spread occurs through water movement, animals, contaminated soil, machinery, vehicles and garden waste dumping.

The Kangaroo Island Landscape Board has been controlling Montpellier broom for over 10 years and over 14 infestations have been found and controlled across the island. The management aims are to destroy all known plants

Montpellier broom is a Weed of National Significance and is a declared pest plant in South Australia under the Landscape South Australia Act 2019 

To help keep Kangaroo Island free of Montpellier broom:

• it is important to report any suspected plants to the Kangaroo Island Landscape Board, and
• practice good hygiene when moving machinery

DESCRIPTION

• Growth form: Evergreen, upright woody shrub usually 1–3 m tall with many branched stems and a deep taproot. Plants can live for 10–15 years and form dense stands.
• Leaves: are soft, hairy and divided into three small leaflets (trifoliate). The central leaflet is slightly larger than the others.
• Flowers: Bright yellow pea-shaped flowers produced in clusters along stems, mainly in late winter and spring.
• Fruit: Narrow, flattened, hairy seed pods about 2–3 cm long. Pods dry and split open explosively when mature.

Seed: Each pod contains about 4–8 seeds, and mature plants commonly produce thousands to over 10,000 seeds per year. Seeds are hard-coated and can remain viable in the soil for more than 20 years, creating a persistent seed bank.

Plant species that look similar are tree lucerne which can be identified by its creamy white flower and native species large-leaf bush pea (Pultenaea daphnoides), narrow-leaf bitter-pea, Kangaroo Island bush-pea (Pultenaea insularis).

IMPACTS

Montpellier broom forms dense thickets that displace native vegetation, reduce biodiversity and alter soil conditions by increasing nitrogen levels. These infestations can provide harbour for pests and may increase fire risk by creating dense, flammable understorey vegetation. In neglected pastures, infestations can reduce pasture productivity and make land difficult to manage. It can significantly affect forestry plantations, particularly in young or recently established stands. 

Mature infestations are significantly difficult to control and have ongoing control costs.

CONTROL OPTIONS

Effective control usually requires a combination of methods and follow-up over many years due to the persistent seed bank. Small plants can be hand-pulled or dug out, while larger shrubs are commonly controlled using cut-and-paint or foliar herbicide treatments. 

Mechanical removal or slashing may be used to reduce dense stands but should be followed by herbicide treatment to prevent regrowth. Maintaining healthy pasture or groundcover can help suppress seedlings. 

Seedling emergence may increase after disturbance or fire, requiring ongoing monitoring. 

Biological control agents are available but are not suitable for small infestation that can be destroyed.

Permitted and on-label herbicides and rates can be found on the PIRSA Weed Control Website

DECLARATIONS

Montpellier broom is declared under the following sections of the Landscape South Australia Act 2019:

• 186(2) Prohibiting movement on public roads
• 188(1) Prohibiting sale of the plant
• 188(2) Prohibiting sale of contaminated goods
• 192(2) Landowners to control the plant on their properties
• 194 Recovery of control costs on adjoining road reserves

FURTHER INFORMATION

Declared Plant Policy - pir.sa.gov.au

Early Intervention Handbook - pir.sa.gov.au 

Weeds Australia - weeds.org.au