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Botanical name: Cytisus scoparius
Common names: Scotch Broom, English Broom, European Broom, Common Broom
Plant family: FABACEAE (pea family)
Origin: Western and Central Europe

Scotch Broom is an erect, woody, long-lived perennial shrub which can grow to about 4 metres. Its green to brownish-green ridged stems are much-branched, and leaves usually have 3 leaflets. The adult growth is often almost leafless.

In spring it bears large numbers of bright golden yellow pea flowers singly or in pairs along its stems. Another form with red and yellow flowers also occurs in the Mountains. Like other members of the Pea family the fruit is a pod, black and flattened, about 5cm long, and hairless. Inside there may be up to 20 brown shiny seeds, reputed to remain fertile for 70 years or more.
 

A World Wide Problem

Scotch Broom has been declared noxious in the Blue Mountains. It has spread to many temperate areas of the world, and has become a weed in many of the countries into which it has been introduced - USA, Canada, New Zealand, Hawaii, South Africa, India, Iran ... It has even become a pest in its own home range. Scotch Broom now occurs in all states, and has been declared a weed in NSW, Victoria, South Australia, Western Australia and Tasmania. Over 200,00 hectares are infested in Australia, and the problem is getting worse.
 

There are significant infestations of Scotch Broom in the Blue Mountains.
 

A Weedy Character

Scotch Broom thrives in moist temperate regions, mainly on slightly acid soils, but tolerates a wide range of conditions, including soils with both high and low levels of phosphorus (a plant nutrient found at high levels in urban runoff). In the Blue Mountains Scotch Broom occurs predominantly above 600 metres. It is spread solely by seed, but it seeds prolifically, an individual plant producing up to 6000 per year. Soil may contain more than 10,000 seeds per square metre.

On hot summer days the mature pods twist and open with an audible crack, and the seeds are ejected up to 4 metres or more from the parent plant. Seeds are also spread by water along drainage lines, by animals, mud on shoes and tyres, by machines such as road graders and slashers, by the movement of contaminated soil - and by dumping in bushland. Young plants establish readily on disturbed sites, and will even survive deep shade.

Changing the Bush

Scotch Broom is a highly invasive weed of bushland, roadsides, disturbed and neglected areas. It grows rapidly, and is extremely competitive with native plants, retarding or preventing the growth of many understorey species, leading to a dramatic loss of diversity. It forms dense thickets, shelters feral animals, and may block tracks and creeklines as it spreads rapidly down them. Around the plants there is a huge build up in the soil of long-lived seeds which germinate when the canopy is removed or the ground surface is disturbed. Scotch Broom is highly flammable and burns intensely, the heat germinating the seed in the soil.

As with many other weeds, Scotch Broom alters the bushland habitat in which it grows - crowding and shading out native plants and preventing the germination of seedlings. In addition to this it changes the soil chemistry by fixing nitrogen and increasing nutrient levels. Thus Scotch Broom can have a profound effect in changing an environment from low nutrient, high light and dry soil to one completely unsuitable for the local native plants.
 

Scotch Broom alters the bushland habitat in which it grows
 

Winning the War against Weeds?

Years of persistent removal of Scotch Broom by Bushcare Groups, the Urban Runoff Control Program, Council's Green Team, and The Great Grose Weed Walk Program had resulted in close to a clean sweep of mature Broom plants across public land in North Katoomba and down the creeklines. But Broom seeds are tough and long-lived in the soil, waiting for the right conditions to germinate, and these conditions were provided by the intense wildfires which swept through North Katoomba and down Katoomba and Yosemite Creeks in December 2002. The hard outer coat of Broom seeds is damaged by fire, and the resulting mass germination of millions of Scotch Broom seedlings in these areas is hard to describe - 'heartbreaking', 'devastating', 'apocalyptic' are some of the words that were used. The threat to the biodiversity of our bushland, creeklines, the World Heritage National Park and the Grose Wilderness is very real.
 

After fire, Scotch Broom seedlings germinate just like
these Cape Broom seedlings
 

The two North Katoomba bushcare groups raised the alarm in January last year, and have been busy ever since, planning their strategies, seeking grants, mobilising the community, and actively weeding out the threat. An impressive 4200 hours of volunteer and professional weeding and regeneration work has resulted in the removal or treatment of 5.5 million weeds from the area, leaving only about half a million to attack. Huge community efforts were put in to remove these plants before they set seed, by volunteer bush regenerators, bushwalkers, members of the Blue Mountains Conservation Society, and community members, supported by the Blue Mountains City Council and National Parks.
 

Volunteers weeding out Scotch Broom - and having a lot of fun!
 

Become involved, and help our bushland! Contact BMCC Bushcare, Katoomba Creek Bushcare Group, Minnehaha Falls Bushcare Group, or National Parks, and find out how you can help. Watch for notice of special activities in the Blue Mountains Gazette. Broom seedlings are easy to remove, and easily identified right now by their bright yellow pea flowers. Timing is critical - seed will set before Christmas, and follow up work will be needed for years. Every hour you can spare will benefit our bush.
 

Home Control of Scotch Broom

Scotch Broom is a difficult plant to eradicate. Slashing causes the plant to coppice (grow new shoots from its cut stem), and the access of light from cutting down the plant brings about the rapid germination of thousands of seedlings. Digging out produces just the disturbance the seeds appreciate. The result can be a much greater problem than before, although seedlings are easily hand pulled.

The best method for the home garden is to kill the parent plant by cutting and painting with herbicide, leaving the root system intact. The resultant seedlings can be pulled by hand, or sprayed if there are no other plants to suffer damage, but, as with Gorse, years of follow-up work will be needed. In many ways, biological control offers the most ecologically sound strategy for the future management of Scotch Broom.
 

Biological Control of Scotch Broom

Current methods of controlling Scotch Broom and many other weeds are expensive and require much follow-up. Scientists are turning increasingly to biological control - that is, using the plants' natural enemies against them. The biological control program is trialling the introduction of a range of agents which attack different parts of the Scotch Broom plant. The aim is to weaken its growth and decrease the amount of seed produced, thus reducing the density and slowing the spread of the weed.
 

The Scotch Broom in an old quarry at Bonnie Doon - targeted for biological control
 

The Cooperative Research Centre for Weed Management Systems (which includes CSIRO and NSW Agriculture) is working in Australia and overseas to extensively research biocontrol agents which must be species specific (ie, they must not attack any plant other than the target - Scotch Broom).

To date, four insects have been released in the Blue Mountains, into an isolated stand of Scotch Broom in Bonnie Doon Falls Catchment: a twig-mining moth, whose larvae mine the shoots, stunting growth and reducing seeding; a plant louse, whose nymphs feed in the buds, causing severe damage to new shoots; a seed-eating beetle, whose larvae feed on the seeds in developing pods, and a seed-feeding weevil.

The volunteer Bonnie Doon Fauna Study Group initially monitored this experimental study of biocontrol of Scotch Broom in the Blue Mountains, in conjunction with NSW Agriculture, CSIRO, and BMCC. Research indicates that a combination of predators will significantly reduce plant vigour and seed production. However, it takes some time for the insect populations to build up enough numbers to have a significant effect on Broom: it is a long term solution to a long term problem. In the meantime, current management practices for Scotch Broom continue in the Blue Mountains.
 

Cape Broom

Also on our noxious weed list is another Broom - Genista monspessulana, variously called Cape Broom, Montpellier Broom, or Genista.

Cape Broom is similar to Scotch Broom in its growth habits, but is a much leafier plant with clusters of smaller yellow flowers on the ends of its branchlets. The seed pod is smaller and densely hairy, and the seeds are black. Cape Broom starts flowering in late winter, and can form dense thickets like Scotch Broom.

Our Responsibilities

Scotch Broom, like Gorse, is classified W2 under the Noxious Weeds Act of 1993. This means that you must fully and continuously suppress and destroy this plant if it is growing on a property you own or occupy. Cape Broom, like Privet, is classified W4b: it must not be sold, propagated or knowingly distributed, and you must prevent it from flowering and fruiting. Failure to comply with a weed control notice issued by Council can incur heavy penalties.
 

Down at the Nursery

Cytisus species with a wide range of flower colours are still being sold at some Blue Mountains plant outlets. They are almost certainly either forms or hybrids of the Scotch Broom, Cytisus scoparius or Montpellier Broom, Genista monspessulana. Their weed potential is not clear, and some may be very weedy indeed. Concerned residents can help make plant sellers aware that we all have a responsibility for our bushland: ask them to check out the Brooms they sell. Ask for a guarantee that they are not invasive.
 

Replacing Broom

Put in some local native plants, and watch the local fauna picnic in your garden! They may even decide to move in permanently.

Yellow-flowered plants to try include Native Dogwood (Jacksonia scoparia); Bush Peas (Pultanaea species); Pea Flowers (Dillwynia species); Wattles, such as Sunshine Wattle (Acacia terminalis); Banksias; Hibbertias; Geebungs (Persoonia species); some Bottlebrushes (Callistemon species) and Grevilleas.

Fauna-attracting small to medium shrubs with flowers of other colours include Hakeas, Correas, Grevilleas, Callistemons Croweas, Baueras, Kunzeas, Waratahs, Melaleucas, Mint Bushes (Prostanthera species), Tea Trees (Leptospermum species) and Mountain Devils (Lambertia formosa). And every garden should have a gum tree - small grafted eucalypts with large stunning flowers are now available.
 

Heraldry and Herbalism

Broom has a long and fascination history in folklore, herbalism and European royalty. As its common names suggest, because of its twiggy nature it has been used since ancient times for sweeping and thatching. But it is also a plant with an aristocratic pedigree, and was once extensively utilised in herbal medicine.

History tells us that Richard d'Anjou, father of England's King Henry II, wore a sprig of Broom in his cap as he rode into battle, some say so that his troops could see it and follow him. But the custom of wearing a Broom sprig in the cap perhaps arose from Broom's ancient reputation as a plant both useful to witches and as a power against them. Whatever the reason, it gained Richard the nickname 'Plantagenet', from Planta genet (Planta genista), the Broom plant. It was adopted by Henry as his emblem - and as his surname, borne by the six Plantagenet kings of England. The device of the broom plant with its opened pods was carved on the tomb of Richard II in Westminster Abbey.

John Gerard, in his Herball (1597) wrote of the memorable Henry VIII, who "...was wont to drink the distilled water of broom flowers against surfeits, and diseases thereof arising." Extracts from the twigs of Broom were taken as a heart tonic, diuretic, emetic and purgative. Nicholas Culpeper (1653) thought Broom also effective against dropsy, gout, ague, black jaundice, sciatica and pains in the joints. The Time-Life Book Herbs (1979) claims that the flower buds can be used fresh in salads or pickled, and that a golden wine can be made from the flowers. Broom is still used in European herbal medicine.

Learn more about Scotch Broom and Cape Broom.