Gorse is a spiny, evergreen shrub native to the western seaboard of continental Europe and the British Isles. It was introduced to the West Coast at Bandon, Oregon, as an ornamental in the 1890s. Gorse infestations are concentrated along the Oregon Coast, particularly on the south coast, with some infestations inland.
Gorse is a legume, a member of the pea family. Gorse produces abundant seed contained in hairy pods 0.5 to 0.75 inch long. The seeds are brown when ripe. Seed can remain viable in the soil for 30 years. Disturbances such as land clearing, timber harvesting or fire stimulate the germination of buried seed. Gorse also can spread vegetatively: If cut, it can resprout quickly. Thus, once established, gorse is difficult to eradicate.
Being a nitrogen fixer, gorse easily colonizes newly disturbed sites, poor sites or sites without vegetation. It often is found along roadsides. On the southwest Oregon Coast, gorse has taken over sand dunes. Its dense, impenetrable stands make the areas unusable for recreation. Gorse outcompetes native vegetation, reducing native plant diversity and degrading wildlife habitat. Dense gorse stands also pose a significant fire hazard because the foliage is highly flammable, and dead foliage collects as litter within and at the base of the plant. Gorse contributed to the Bandon Fire of 1936, in which the entire town nearly burned to the ground.
Gorse can grow up to 15 feet tall and 10 to 30 feet in diameter, forming a dense, compact shrub (Figure 1). Gorse has bright yellow, pealike flowers 0.5 to 0.75 inch long at the end of branches (Figure 2). Branches are dark green with conspicuous spines. Juvenile leaves are trifoliate, and spines develop as the branch matures.
You can learn how to prevent, reduce and control gorse on forestland, which has specific herbicide regulatory requirements. There are also practical considerations for controlling gorse in reforestation areas.
Management options
Several methods will prevent, control or reduce gorse. The first strategy is preventing gorse from gaining a foothold on your property. If you already have gorse on your property, the most effective ways to control gorse entail a combination of chemical, mechanical and biological methods. Well-established gorse may be impossible to eradicate, but it can be reduced significantly.
Prevention
Prevention is key to reducing new gorse infestations. Be sure to clean mechanical equipment to rid equipment of seed before using the equipment on other sites. If you spot new gorse plants on your property, immediately pull or treat them to prevent a large infestation. Look for new gorse patches when gorse is in peak bloom, from January to March. Note the location on a map or mark the area on the ground. After treatment, go back and monitor the area annually to determine whether control has been successful. Re-treat if necessary.
Chemical control
Note: Read and follow herbicide labels carefully. Before spraying over or around tree seedlings, ensure the chemicals pose no hazard. Before you apply herbicide on forestland, you must file a “notification of operations” with the Oregon Department of Forestry at least 15 days in advance. Consult your local Extension agent or Oregon Department of Agriculture representative for specific recommendations for your situation.
Gorse can be controlled with herbicides from spring through fall. Fall is often the best time, as plant carbohydrates move down into the roots along with the herbicide, killing the root system. Year one is critical in a long-term management plan. Spray gorse resprouts within six months of completing mechanical removal or mulching. There are two options:
- Grind and mulch in spring, followed by spraying gorse resprouts in fall.
- Grind and mulch in fall, followed by spraying gorse resprouts in spring.
Triclopyr products are the best herbicide option for gorse control and can be mixed with other herbicides shown in Table 1. Please note that some herbicides listed should not be used near water. All the herbicides mentioned in Table 1 are labeled for use in forestry applications. Follow all label recommendations — the label is the law.
| Product Name | Chemical | Application method | Comments |
|---|---|---|---|
| Ultra, Element 4 (Garlon 4) | triclopyr ester | Foliar spray | Do not apply near water. Avoid applying on warm days to prevent volatilization. |
| Vastlan (Garlon 3A) | triclopyr amine | Foilar spray or cut stump | Can use near water. Apply full- or diluted-strength for cut stump treatments. |
| Escort | metsulfuron | Foliar spray | A soil-active herbicide that controls germinating weeds. Do not apply near water. |
| Capstone | aminopyrid+tricolopyramine | Foilar spray or cut stump | Apply soil-active herbicide that controls germinating weeds. Not for release, unless a directed spray. |
| Opensight | aminopyralid+metsulfuron | Foliar spray | A soil-active herbicide that controls germinating weeds. Do not apply near water. Can be used for releasing tree seedlings. Caution: for conifer release, spot sprays can injure seedling foliage. For site preparation, delay planting tree seedlings for two months west of the Cascades and four months east of Cascades. |
When foliar spraying, it is critical to use a good surfactant (methylated seed oil or silicone-based) and thoroughly wet the entire plant. Any untouched surface, even the undersides of branches, will survive. The cut stump method can be an effective way to kill larger plants. Cut the main stump and apply herbicide to the cut surface, where it will be carried down to the roots. Read the label carefully to ensure that you don’t exceed application rates.
In any herbicide treatment program, rotate among chemicals to prevent the development of herbicide-resistant strains of the weed. For details on herbicide resistance, refer to the current edition of the PNW Weed Management Handbook. For information regarding vegetation control approaches in forestry applications, including the susceptibility of conifers to herbicides, see the Forestry and Hybrid Cottonwoods section of the PNW handbook.
For pollinator protection information, see How to reduce bee poisoning from pesticides.
Mechanical control
Chopping, cutting and mowing can work in areas accessible to machinery. Hand pulling aided by a weed wrench and digging with large equipment can be effective on individual or small groups of plants. In areas where large stands of gorse are extensive, use excavators with heavy-duty or masticating mowing heads to grind gorse to a mulch. Leaving mulch in place helps keep gorse seeds from germinating. Use herbicide or grazing animals to control resprouting after mechanical removal. Note that all mechanical methods disturb the soil and may encourage dormant seed germination in the soil. On steeper ground, you may have to cut it by hand with chain saws. Wear protective clothing and gloves. To prevent spreading gorse seed, thoroughly clean equipment and vehicles on site before moving equipment to new areas.
A combination of mechanical and herbicide methods provides the most effective gorse control:
- Step 1: Use mechanical equipment in a slow and deliberate manner, with a goal of grinding gorse stems and mulching gorse material on site.
- Step 2: Within six months, spray gorse resprouts and seedlings (spring or fall) with a site- appropriate Triclopyr product.
- Step 3: Re-treat regrowth and seedlings each year.
Grazing
On pastureland that is being converted (planted) back to forest, goats, sheep and cattle can graze small gorse seedlings if foliage is tender to help prepare the site for tree seedlings. Continual grazing in an area reduces the number of plants and inhibits seed production. Intensive grazing should occur one to two years before tree seedlings are planted to avoid browsing damage. To eradicate gorse in these areas, however, grazing must be combined with mechanical and chemical control measures.
Conifer shade
Some long-term studies have shown that shade can help deter gorse development. Planting conifers may be effective in the long run if successfully established to create dense canopy shade. Plant large, bare- root seedlings at a density of 10 feet by 10 feet or 12 feet by 12 feet. Planting at a closer spacing (9 feet by 9 feet) may expedite canopy closure but will require precommercial thinning at age 12–15 years.
Control of gorse in conifer plantations requires careful spot spraying during the conifer dormant season to avoid damaging conifer seedlings. Using black plastic mulch mats can also reduce competition from gorse and other competing vegetation to boost the survival and growth of tree seedlings. Use mats that are 4 feet by 4 feet. Secure mats to the ground with rocks, debris or pins so that they don’t blow away or cover the seedlings and smother them.
Biological control
Biological controls for gorse approved for release in Oregon include:
- Seed weevils: The seed weevil consumes gorse seeds and spines. The weevil destroys between 20% and 60% of seed, reducing seedling recruitment and overall spread.
- Spider mites: These insects feed on leaves, killing branches but rarely the entire shrub.
- Thrips: These insects feed on gorse foliage. As of 2024, thrips are established in Oregon and beginning to spread; researchers will assess impact levels in the coming years.
For more information on biological controls and photos for identification, see the Oregon Department of Agriculture.
Use pesticides safely!
- Wear protective clothing and safety devices as recommended on the label. Bathe or shower after each use.
- Read the pesticide label—even if you’ve used the pesticide before. Follow closely the instructions on the label (and any other directions you have).
- Be cautious when you apply pesticides. Know your legal responsibility as a pesticide applicator. You may be liable for injury or damage resulting from pesticide use.
