White Weeping Broom (Retama raetam)

Description

White Weeping Broom (Retama raetam) is a Mediterranean shrub that grows to about 3 m tall and may reach 6 m across. Stems of young plants are covered with long soft hairs but become hairless with age. Young plants are wispy with a single stem and strong taproot. Plants are grey-green with slender, drooping branches. The leaves, which are very small (about 5 mm long) and narrow (only 1 mm wide), are quickly dropped and the plant remains leafless for most of the year. Flowers are 8-10 mm long, white and pea-like, in racemes of 3-15 flowers. Each flower has 10 stamens forming a closed tube. The seed pod is glabrous and 10-15 mm diameter, each with one or two kidney-shaped seeds, which are about 6.5 mm long and may be yellow, green, brown or black in colour.

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

Distribution:

In Australia White Weeping Broom has become naturalised in South Australia, particularly around and to the east of Adelaide, on the Yorke Peninsula where it has taken over an area planted to native vegetation, and on the Eyre Peninsula where it is invading She-oak (Casuarina, Allocasuarina) woodlands. In Western Australia it grows around and to the north of Perth.

Habit:

Shrub

Key points:

White Weeping Broom (Retama raetam) is an aggressive invader which spreads by seed, each plant producing a large number of seeds.

It is a very drought-tolerant species, making it a particular threat in dry regions and during drought years.

Prevention and early intervention are the most cost-effective forms of weed control. It is important to identify existing sources of White Weeping Broom, such as garden specimens, and remove them before they invade natural ecosystems.

How it spreads:

White Weeping Broom reproduces from seed. Each plant produces hundreds of seed pods and up to thousands of seeds on larger plants. The seeds drop when the seed pods split open, and can be further spread by water. A hard seed coat renders most seeds dormant initially, but as the seed coat wears away germination can take place. Seeds remain viable in the soil for several years.

Where it grows:

Like many of the Broom plants, it invades nutrient-poor to fertile, well-drained (especially sandy) soils where it can fix nitrogen and form a scrub layer that can out compete and shade out native plants. This species is possibly the most drought tolerant of the exotic Brooms in Australia, making it a particular threat in dry regions and during drought years. It may infest grazing land and prevent access to stock. It is also probably the least palatable to stock of the exotic brooms. While it has high tolerance to drought and frost and moderate fire and salt tolerance it is not tolerant of waterlogging.

Flower colour:

White

Distribution map:

Impacts:

White Weeping 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.

White Weeping Broom has the potential to become a significant threat to Australia’s pastoral industry if it escapes containment. It is a potentially serious invader of natural vegetation. It may infest grazing land and reduce access by stock. In addition, it is unpalatable and toxic. The toxins in the plant can taint milk and may poison nursing animals. It could reduce carrying capacity of grazing lands by more than 5%.

Origin:

White Weeping Broom is native to northern Africa and western Sahara, Sicily and the Middle East. In its native range, White Weeping Broom grows in grasslands in the Mediterranean region and is a common feature of deserts and grasslands in the Sahara.

History:

White Weeping Broom was brought to Australia as an ornamental shrub. It was first recorded in South Australia in 1841.