Gorse (Ulex europaeus) reduces the area available for grazing by livestock on pasture land and invades naturally open spaces. Broom (Cytisus scoparius) is an aggressive plant pest, which is unpalatable to stock and will reduce stocking rates. Find out how to recognise gorse and broom and what to do if you find them.
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Why they are pest plants
Gorse is widespread throughout the Waikato region, reducing the area available for grazing by livestock on pasture land and invading naturally open spaces. The foliage of gorse can become dry, making gorse stands susceptible to fire.
Broom is an aggressive pest plant, which is unpalatable to stock and will reduce stocking rates. It is an agricultural plant pest but also causes problems in forestry, waste-lands, along road and rail sides, braided rivers and protected natural areas. Broom is particularly a problem in the open tussock grassland of the North Island central plateau.
How to recognise these pest plants
Gorse is a deep-rooted woody perennial that can grow up to four metres high.
Broom is a deciduous shrub most recognisable by its distinctive upright green stems. Broom normally grows in areas of high rainfall and can tolerate a wide range of soil conditions.
Identifying features
Gorse
- Leaves of gorse take the form of sharp spines.
- The plant can grow up to four metres tall.
- Gorse's yellow pea-like flowers grow into brownish black flattened seedpods.
- Seedlings initially have more conventional leaves, which are trifoliate (three leaflets).
Broom
- Broom is an erect deciduous shrub growing up to 2.5 metres in height.
- Flowers are large, yellow and bloom from October to November. Seed pods are similar to gorse.
- Broom has pliable, upright, ridged green stems that may have small leaves, but may also be leafless.
Responsibility for control
All land occupiers in the Waikato region are required to destroy all gorse and broom plants within 20m of their boundary. All quarries and road and rail verges must be kept completely clear of gorse and broom.
Gorse and broom are declared total control plant pests for all quarries and road and rail verges, requiring all plants to be destroyed in these areas. The sale, propagation or distribution of gorse and broom is prohibited throughout the Waikato region.
How to control gorse
Mechanical control
A hand slasher or scrub cutter can be used on isolated bushes but if the stump is not treated with a herbicide (see stump treatment below), re-growth will occur. Large areas of slashed stumps can be left to grow to 0.5 metres in height and then sprayed.
Herbicide control
Many herbicides are not effective on gorse because of the shape of the 'leaves' and the thick cuticles on the spines, which help prevent absorption of herbicides. However, gorse can be killed using such herbicides as GrazoneR, TordonR Brushkiller, EscortR and RoundupR or stump treated with Vigilant TM gel.
Hard grazed gorse or recently slashed gorse is difficult to control because of reduced foliage to take up herbicide. Active growth is more susceptible to spraying. Your Biosecurity Plant Pest Contractor can give you advice on the timing and method of application best suited to your situation.
How to control broom
Mechanical control
Young plants can be hand pulled or grubbed. This method of control should be carried out before seeding. Small bushes can be slashed and the area cultivated. However, this will produce a seedbed suitable for the establishment of seedlings. These areas should then be controlled by further cultivation or heavy grazing.
Herbicide control
Chemical control is effective. A 'blanket' spray during the full leaf stage (spring to early summer), followed by maintenance spraying of any further growth is effective. All the herbicides suggested for controlling gorse (above) can be used to control broom. The use of penetrants may increase effectiveness of control. Your Biosecurity Plant Pest Contractor can give you advice on the timing and method of application best suited to your situation.
Summary of herbicides for control
When using herbicides:
- read the instructions on the manufacturers label closely
- always wear protective clothing
- always minimise the risk to desirable plants
- contact the supplier for further advice
- for aerial and boom application rates contact the supplier.
Biological control
Six separate biological control agents for gorse have been released within the Waikato region. The most successful of these has been the gorse spider mite (pictured). Four broom agents have been released including the broom seed beetle, broom twig miner and broom psyllid.
Manaaki Whenua – Landcare Research runs a national biological control programme. Environment Waikato supports this programme and maintains a local biological control programme for the Waikato region. Have a look at the Landcare Research website for more information on bio-control agents.
Further information
For additional advice and information on effective methods of control, contact your Biosecurity Plant Pest Contractor or call 0800 BIOSECURITY (0800 246 732).
For more information on pest plants or the use of agrichemicals phone Environment Waikato's freephone 0800 800 401.
For more information on pest plants, check out the Weedbusters website.
Related publications
Visit our Waikato Regional Pest Management Strategy.
'What makes a pest a pest? - A guide to Waikato's pest management future' - download (730 kb, 104 seconds to download, 56k modem) order or pick up for free from our offices.
Pick up or order 'Plant me instead - Plants to use in place of common pest plants' for free from our offices.
Download the National Pest Plant Accord.
Pick up or order 'Poisonous plants and fungi in New Zealand - A guide for parents, schools and child minders' for $15 from our offices.