White Spanish broom is a serious environmental weed in Victoria and is targeted for eradication. Like all brooms, it invades a wide range of fertile soils where it can fix nitrogen and form a dense scrub layer that outcompetes native species. It also provides shelter for feral animals and its seeds are poisonous. In pastures white Spanish broom forms thickets that prevent grazing and restrict access to water.
White Spanish broom is native to Portugal, Spain and France. It has also been introduced as an ornamental in India, Australia, Italy, United States, New Zealand and Argentina. In Australia it has become a weed and is quite common in central Victoria. It has been eradicated from the Mount Lofty Ranges in South Australia.
White Spanish broom generally spreads by seed, with most seed falling within 1 m of the parent plants. It may be spread over longer distances by movement of seed by water or in mud attached to vehicles, machinery, footwear and animals. Like many legumes, white Spanish broom is hard seeded and the seeds remain viable for a long time in the soil, probably as long as the seed of the closely related C. scoparius (Scotch broom), which is still viable 20 years after being dropped. Germination of C. scoparius seed is greatest once the hard seed coat is breached by fire, and this mechanism is also likely to be required by white Spanish broom. Infestations may also spread locally through plant pieces taking root.
White Spanish broom is a large shrub which grows to 3 m high and has striped green stems.
The leaves are arranged in groups of three leaflets on lower branches and a single leaflet on higher branches. Young stems and leaves are covered with short hairs which are lost as the plant ages. White Spanish broom has finer, greyer foliage than broom.
Both the flowers and seed pods are pea-like. The flowers are white with a pink streak at the base and 9–12 mm long. The seed pods are covered with short hairs and are generally 15–27 mm long and 4–7 mm wide. The pods turn black when mature and release seeds explosively when ripe. Each pod contains between three and seven seeds, which are 2.5–3.0 mm long and olive to brown in colour.
Little is known of the environmental requirements of white Spanish broom. As a weed, it is known to enter relatively undisturbed bushland. In Australia it has spread from lakeside plantings into roadsides and townships, but it could also establish in a wide range of disturbed and undisturbed habitats such as grasslands and open eucalypt woodlands.
CRC for Australian Weed Management: Andy Sheppard (CSIRO/Weeds CRC), John Hosking (NSW Agriculture/Weeds CRC), Eddie Talbot (West Coast Weed Strategy, Tasmania), Michael Hansford (Vic DPI) and John Thorp (National Weeds Management Facilitator).
Because there are relatively few white Spanish broom infestations, and it can potentially be eradicated before it becomes established, any new outbreaks should be reported immediately to your local council weed officer. Do not try to control white Spanish broom without their expert assistance. Control effort that is poorly performed or not followed up can actually help spread the weed and worsen the problem.
Although there has only been relatively limited research into the effectiveness of different control methods on white Spanish broom, field tests have shown that it is relatively easy to kill by using mechanical and physical removal, herbicides and burning. The methods that are useful on broom (C. scoparius) will also be effective for white Spanish broom, including the ‘cut and mulch’ method outlined in the case study above and recently used in Tasmania. Note, however, that any attempted control of white Spanish broom should be undertaken cooperatively with your local council and or neighbours.
Physical removal is an option for isolated plants, particularly if they have not seeded. Bulldozing infestations into heaps and burning the resulting weed mounds has been a common method used to control broom but it only provides a temporary solution. Bulldozing causes massive soil disturbance and physical movement of plants, not only burying seeds but also spreading them beyond the original infestation. In at least one place this practice and a lack of follow-up monitoring and control has exacerbated the broom problem.
Herbicides offer control of broom, especially in preventing spread from small isolated patches, but there are currently no herbicides that are registered for use on white Spanish broom. For more information on the use of herbicides contact your local council weed officer.
Fire is a useful tool in controlling broom and managing the large, long-lived seedbank. In a farming situation fire can remove the bulk of plants and encourage germination of broom seed stored in the soil. The intensity of the fire is very important – it needs to be hot enough to stimulate the bulk of the broom seedbank but not too hot as to destroy the native seedbank. With enough light and moisture, broom seedlings will quickly re-establish and the site will become covered in a thicket of broom again, which must be controlled before flowering. Natural revegetation from native seeds can then occur; otherwise, sowing of suitable pasture species may be required. Fire is relatively cost-effective, although it may require grasses as fuel, thus reducing pastoral productivity. Permits may be required to light fires.
Grazing with goats or sheep is suitable for pasture, especially on new growth following fire. Fencing areas of broom into small paddocks and grazing these areas with goats has been successful.
Once an area of broom has been treated, it will be necessary to monitor the area for many years and to control any new plants, even in areas where there is good revegetation.
White Spanish broom (Cytisus multiflorus) is not declared in NSW under the Noxious Weeds Act 1993.