Gorse

(Ulex europaeus)

What is gorse?

Images top & above left: gorse flowers.

Images above centre & right: gorse invading river bank & bushland.

Pest Genie

Do

• Plan your control program, this will save time and money in the long-run;
• Use a combination of different control methods;
• Consider the impact of your control methods on off-target things, especially if herbicides are used;
• Ensure machinery and equipment is washed down between sites or prior to contractors leaving site;
• Revisit the site and use follow-up treatments over at least 5 years;
• Coordinate your control program with neighbouring landholders where your gorse problem crosses property boundaries;
• For large infestations, tackle the smaller, outlying patches first. The larger infestation can be tackled later.

Don't

• Don't introduce gorse to gorse-free areas (e.g. by failing to wash down machinery and equipment between sites);
• Don't start your control program without first planning your approach;
• Don't rely on just one control method;
• Don't rely on one attempt at removal - follow-up is essential;
• Never burn gorse without follow up treatment of regrowth;
• Don't burn gorse in or next to native vegetation.

Spread of gorse

• Gorse reproduces by seed; each plant produces huge numbers of seeds with a water-resistant coating which allows them to remain dormant in the soil for up to 30 years.
• Seeds are usually released in hot or dry conditions but can be stimulated into germination following burning or mechanical disturbance. Most seeds fall around the parent plant but the pods can split open and shoot seeds for a distance of up to 5m, allowing infestations to spread rapidly.
• Gorse can also spread from seed movement in water, soil, machinery and footwear. Individual gorse bushes can live for up to 30 years.
• See the Washdown Guidelines for Weed and Disease Control for detailed information on how to wash-down equipment and personnel to reduce the chance of spreading gorse.

Avoiding the introduction of gorse

• Preventing the introduction of gorse to gorse-free areas is the best means of control. Good machinery and equipment hygiene-practices are vital.
• Gorse seed is usually carried into new areas in soil and mud attached to machinery or boots. Gorse seed is too heavy to be dispersed by wind, and birds are not important in spreading seed.
• Gorse seed can also be carried in water. Removing gorse bushes on the edges of water courses is important in preventing dispersal of seed downstream.

Physical removal

• Physical removal of gorse will not control an infestation unless it is combined with other methods of follow-up control. Regular slashing or mowing by themselves are NOT effective in eradicating gorse because plants will regrow from cut stumps or dormant seed in the soil as soon as slashing ceases.

Cultivation

• Mechanical clearing is an ideal method of controlling large infestations on land that is later sown down with a competitive pasture species. This treatment may require targeted herbicide spraying of regrowth and a second subsequent sowing of pasture.
• Avoid causing unnecessary disturbance to the soil, and avoid using heavy machinery along creeks and rivers.
• Follow-up management is vital. This includes establishment of a vigorous pasture, grazing of gorse seedlings, and herbicide use on plants surviving grazing.

Burning

• Frequent burning of gorse without follow-up will lead to increased germination of seed and more gorse. Burning should ONLY be used in conjunction with other control methods.
• Burning is useful for removing large stands of gorse and making follow-up spraying more effective. Fire destroys large amounts of seed and stimulates much of the remaining seed to germinate, so that the seedlings can be sprayed the following year, greatly reducing the seed in the soil.
• Burning can be useful several months after spraying of an infestation as it reduces the dead stems to ashes.
• Burning can be useful when combined with grazing by sheep or goats. Burning will reduce the amount of mature (and unpalatable) foliage and stems of older bushes, as well as stimulating the growth of seedling-shoots which are more palatable to grazing animals.
• Gorse burns readily and gorse fires may cause severe damage to adjacent bush. Extreme care should be taken when burning gorse near native vegetation, fences or buildings. Gorse growing underneath high voltage power lines should not be burned without consulting the power company.

Grazing

• Grazing can be useful when combined with other control methods such as burning and herbicide, but is usually not effective on its own at eradicating gorse.
• Grazing by sheep is only moderately effective at controlling regrowth gorse seedlings. Sheep will browse gorse bushes during spring or when pasture feed is in short supply. However, sheep prefer pasture to gorse, and control of established plants cannot be achieved by sheep grazing alone.
• Goats prefer to browse young gorse shoots rather than pasture. However well established gorse bushes are not readily killed by goat browsing alone, and will recover when the goats are removed.
• One strategy is to burn mature gorse bushes, then stock with goats supported by large numbers of sheep during spring and early summer to reduce pasture carry-over. Reducing pasture carryover into late summer/autumn by sheep-grazing in the spring means that goat browsing pressure can be maintained on the gorse bushes throughout the growing season.

Biological control

• Biological control is the use of a living species, usually an insect, mite or disease, to control a weed;
• Biological control will not eradicate gorse, but can be used in conjunction with other control methods;
• Biological control agents that have been released in Tasmania include the gorse seed weevil, gorse spider mite, and gorse thrips.
• These gorse control agents can be released into heavy infestations to reduce the vigour and abundance of the gorse to assist with other control methods as part of an integrated management program.

Chemical control

• A number of herbicides are registered for use on gorse in Tasmania. See Herbicides for Gorse Control for more detailed information.

Sensitive environments

There are a number of sensitive environments where gorse often occurs, and care is needed in selecting the control method in these environments:

Creeks, rivers and wetlands

• Consider using non-herbicide methods for gorse along waterways and in wetland areas as chemicals can have significant off-target effects in these environments.
• If there is no alternative, then ensure that the appropriate herbicide and application techniques are used.
• Avoid using heavy machinery that may cause damage to stream-banks and trigger erosion.
• Gorse control along rivers should be done in conjunction with stock control and revegetation.
• For more advice, contact Biosecurity Tasmania on 03 6165 3777.

Native bushland

• Avoid clearing with heavy machinery and burning for controlling gorse infestations in native bushland.
• Re-vegetate with local native species.
  

Integrated management of gorse

In most situations, the most effective control of gorse will be achieved by a combination of the above methods rather than using a single method. To maximise the chance of successfully eradicating an infestation, it is imperative that after removing or spraying gorse the site is monitored for regrowth over several years, and any regrowth is dealt with by follow-up control.

Agricultural land

In agricultural situations, herbicide application, burning, mechanical removal, pasture establishment and goat and sheep grazing can be combined successfully.

In most agricultural situations gorse bushes should be removed after spraying to facilitate the preparation of a seedbed, the sowing of pasture seed and the herbicide treatment of regrowth. Removing the dead gorse will also reduce the fire hazard created by the dead bushes. Sprayed bushes should not be removed until full brownout has occurred. Burning the dead gorse is also an effective way to reduce the seedbank prior to re-sowing.

Wasteland areas

In wasteland areas such as gullies and rocky banks where pasture establishment is impractical, spraying or cut-stump treatment with repeated follow-up treatment are the most effective ways of preventing reinfestation. In these areas, grazing should be restricted to prevent soil disturbance and encourage the natural regeneration of grasses and other plants to compete with gorse seedlings.

Bushland areas

For bushland areas, mechanical methods (chainsaw, brushcutter), herbicide application (cut stump treatment) and revegetation can be combined to control gorse with minimal damage to surrounding vegetation. Removal by burning will encourage the germination of gorse and other weeds which will rapidly cover bare areas left after the fire. Therefore, dead gorse bushes should be removed by other means with minimal soil disturbance. In the case of wildfire in bushland, areas known to have had gorse should be inspected for treatment of germinating gorse seeds following the fire.