White Spanish Broom (Cytisus multiflorus)

Description

White Spanish Broom (Cytisus multiflorus) is an erect, deciduous shrub to 4 metres high with numerous stems. The stems are rounded in cross-section, longitudinally ribbed and covered with short silvery hairs when young. Plants are often leafless when in flower. Leaves are arranged in groups of three leaflets on the lower branches and single, stalkless leaflets on the higher branches. The silvery-silky leaflets are linear-lanceolate or narrow-oblong, to 12 mm long and 4 mm wide, with a pointed or blunt and rounded tip.

The pea-like flowers are white with a pink streak at the base and are approximately 8 -12 mm long.

The seed pods are covered in short hairs and are linear-oblong, 20-30 mm long and 4-6 mm wide. They turn black at maturity and release seeds explosively when ripe. There are mostly 3-6 ovoid to globose seeds in each pod, each about 2.5 mm long and olive-green to brown in colour.

For further information and assistance with identification of White Spanish Broom contact the herbarium in your state or territory.

Distribution:

The only definitive naturalised records of White Spanish Broom are from central Victoria where it has been recorded from three sites - Taradale near Castlemaine, St Georges Lake at Creswick, and at a cemetery in Ballarat.

Habit:

Shrub

Key points:

• White Spanish Broom (Cytisus multiflorus) is currently only known with certainty from three sites in central Victoria.
• It is a serious environmental weed of native forest at Creswick, Victoria, naturalised over about 50 hectares.
• If not eradicated or controlled it has the potential to expand its range much further, threatening to invade a variety of natural ecosystems in the same way as the closely related Cytisus scoparius (Scotch Broom).
• Currently it has not impacted on agriculture or forestry, but the potential for serious impacts is great.
• Control is difficult, and methods similar to the control of Scotch broom can be used.

How it spreads:

White Spanish Broom is spread mainly by seeds, which are ejected explosively as the pods dry out on warm, sunny days during summer. Most of the seeds fall within 1 metre of the parent plant. They are further dispersed by water (particularly if near streams), mud on machinery (such as road graders, slashers), vehicles and footwear.Some authorities cite birds, ants, cattle, horses, animal diggings as being other means of dispersal for the similar species Scotch Broom.

Where it grows:

In south-western Europe, where White Spanish Broom is native, it grows in the woods, heaths and river banks. The Mediterranean climate from where it originates, makes it well adapted to the climate in southern Australia. In the United Kingdom, where it is naturalised in northern Wales and southern England, it grows on banks of roads and railways. In New Zealand it is naturalised on the North Island, and it grows in dry waste places, scrubland, and riverbeds.

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.

White Spanish Broom was first collected from along a watercourse. The current main incursion in Victoria is beside St Georges Lake, with records from the National Herbarium of Victoria noting its original occurrence at this site along the spillway embankment. Contemporary collections in the National Herbarium of Victoria note that it is naturalised in weed invaded Eucalyptus forest on Ordovician deposits.

Flower colour:

White

Distribution map:

Impacts:

White Spanish Broom is on the Alert List for Environmental Weeds, a list of 28 non-native plants that threaten biodiversity and cause other environmental damage. Although only in the early stages of establishment, these weeds have the potential to seriously degrade Australia’s ecosystems.

Information about the ecological and economic impacts of White Spanish Broom in other countries where it is naturalised, as well as in Australia, is scarce. White Spanish Broom is a serious environmental weed at the St Georges Lake, Creswick area, which is the largest infestation in Australia, over ca. 50 hectares through a Eucalyptus forest. Its potential for spread and impact if not eradicated is much greater, given its close affinity with Scotch broom (Cytisus scoparius).

While its main threat currently is as an environmental weed, reducing native biodiversity and landscape aesthetics, it has the potential to invade pasture and forestry. Currently there are no reported cases of impact on livestock in Australia.It is believed White Spanish Broom as being poisonous. The seeds of the related species Scotch broom are poisonous if ingested in quantity, and the foliage may cause digestive problems in horses.

The purportedly closely related Scotch Broom is a highly invasive species in the cooler, higher rainfall areas of south-eastern Australia and has become widely naturalised in many regions. It is a major environmental weed in the Barrington Tops National Park in New South Wales, where it has infested an area of approximately 10 000 hectares. It is also a problem in the Blue Mountains, New South Wales. In Victoria, it is a serious problem in the central highlands, particularly in the Ballarat-Creswick-Daylesford districts, where it is a serious invader of native forest and roadsides in this area. It is also abundant in the Mitta Mitta River valley around Lake Dartmouth. It is also problematic in the Mount Lofty Ranges in South Australia, as well as a problem in parts of Tasmania. More than 200 000 hectares of land in eastern Australia has become infested with Scotch broom, and despite attempts to control it, it continues to spread.

Origin:

White Spanish Broom is native to south-western Europe: France, Portugal, and Spain. It is also naturalised in Argentina, India, New Zealand, United Kingdom, and western USA.