What does it look like?
Gorse is a deep-rooted, woody perennial shrub that can grow to 4m tall. It has densely spined branches and is woody when mature. Gorse has bright yellow flowers from May to November, and black seed pods in summer. Gorse seed reserves in the soil are long-lasting and abundant under and near established infestations.
Why is it a problem?
Gorse is a very invasive plant that has established on thousands of hectares of hill and less intensively farmed country across New Zealand and can form vast areas where it is the dominant species. In dry hot summer weather, a gorse fire burns very hot and is a significant risk.
Gorse has the ability to occupy a wide range of soil types including light sands, heavy clays and disturbed soils, and recovers easily after burning. It is quick to colonise new areas, forming dense thickets. Habitat includes riverbeds, pasture, scrubland, roadsides and waste land, as well as low growing or regenerating native vegetation and forest margins.
An established hedge can produce up to 6 million seeds per hectare per year. Flowering begins when the plant is around 18 months old and usually happens during spring and autumn. In cold climates, flowering may only occur once a year, but flowers can remain year-round when conditions are favourable. Bushes can live for up to 30 years.
As a member of the nitrogen-fixing family, gorse can promote healthy soil nutrients levels, and depending on the native species growing, this may or may not be an advantage. Gorse is also referred to as a 'nursery plant' as it shelters young plants and then slowly dies off due to its shade intolerance, as native species begin to create a canopy cover. This process can take decades.
Control methods
Physical control
Sites with appropriate native tall forest species can usually be left to be overtopped. Exclusion of grazing stock is essential. This can also be sped-up by selective slashing, stump swabbing, or planting.
Herbicide control
Stump swab with 250ml glyphosate (360g/l) per 750ml water or 2g metsulfuron-methyl (600g/kg) per 1L water or 250ml triclopyr (600 EC) per 750ml water or 100ml Tordon Brushkiller per 1L water or Vigilant gel. Or
Spray (spring-summer) use 60 ml triclopyr (600 EC) per 10L water.
Spray (autumn-winter) use 5g metsulfuron-methyl (600g/kg) + penetrant per 10L - knapsack or (35g/100L + penetrant - spraygun) or Tordon Brushkiller (250ml/100L spraygun).
Frilling: With a sharp chisel or axe, make a deep cut into the sapwood at regular intervals around the base of the tree, taking care not to ring-bark the plant. Immediately saturate each cut with undiluted Tordon Brushkiller.
Drill and fill: Drill 10-12mm holes around trunk at 200mm spacing and fill with undiluted Tordon Brushkiller using a sheep drench pack with a spraygun.
CAUTION: When using any herbicide or pesticide PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.
Related links
https://www.nzpcn.org.nz/flora/species/ulex-europaeus/
https://www.weedbusters.org.nz/what-are-weeds/weed-list/gorse/
Management Programme
Sustained Control Programme
To provide for ongoing control of the subject, or an organism being spread by the subject, to reduce its impacts on values and spread to other properties.
Rules
Rule 18 - blackberry and gorse plants
All occupiers shall, on receipt of a written direction from an Authorised Person, destroy all plants within 10 metres of the property boundary; and on land that they occupy where an adjoining occupier is also destroying or the land is clear of, all plants within 10 metres of the property boundary; Council will administer the rule upon receiving a written complaint from the adjacent land occupier and/or at the discretion of the Authorised Person.
