Brooms Weed Management Guide Brief

Brooms: Scotch (Cytisus scoparius), Montpellier (Genista monspessulana) and flax-leaf (Genista linifolia) brooms Weed Management Guide Weed of National Significance Brooms: Scotch , Montpellier (Cytisus scoparius) (Genista and flax-leaf brooms monspessulana) (Genista linifolia) Scotch broom in flower. Photo: Matt Baker. Montpellier broom. Photo: Hillary Cherry. Flax-leaf broom. Photo: Matt Springall. Key points • Brooms shade out native vegetation and can impact forestry and grazing lands. • Rapid growth and an ability to increase soil nitrogen enable brooms to out-compete desirable native plants and plantation species. • Brooms produce masses of long-lived seed that can be spread long distances by animals, humans and water. • Plants regenerate quickly after disturbance, such as fire. Broom infestations can also increase the risk and intensity of fire. • The integrated use of chemical, mechanical and biological controls over the long term can help to effectively suppress and control broom infestations. • Management activities can often promote broom germination, thus follow-up and further restoration are essential. The problem purposes. Brooms are now widespread undisturbed areas. If not controlled, across parts of southern Australia, they can modify native ecosystems by Brooms invade native vegetation, where they form dense infestations increasing the frequency and intensity plantation and pastoral systems that damage conservation and of fire, changing vegetation structure, in Australia causing significant production assets. altering soil chemistry and providing environmental and economic impacts. harbour for invasive animals. Broom Three species are recognised as Weeds Broom species grow quickly, produce invasion may also affect native animals, of National Significance (WoNS): Scotch large amounts of seed and can tolerate contributing to changes in species (or English) broom, ; diverse environmental conditions. They Cytisus scoparius diversity and density. also increase soil nitrogen which, in Montpellier (or Cape) broom, Genista turn, creates ideal conditions for broom Although effective control measures monspessulana; and flax-leaf broom, regeneration. Brooms establish rapidly for brooms exist, their ability to rapidly Genista linifolia. They are native to Europe, but have been widely cultivated after disturbance, such as fire or re-establish from a persistent seed across Australia for ornamental grazing, but can also invade relatively bank necessitates intensive follow-up 1 Brooms: Scotch (Cytisus scoparius), Montpellier (Genista monspessulana) and flax-leaf (Genista linifolia) brooms Montpellier broom invasion. Photo: Hillary Cherry. Scotch broom: note five-sided stems and hairs along pod edges only. Photo: Hillary Cherry. Montpellier broom flowers and leaves. Photo: Brad Rayner. Flax-leaf broom leaves and pods. Photo: Jackie Miles. and site restoration. Large infestations of the rotation, as the increased when grazed intensively. Brooms can also require integrated management using a competition for resources interferes with hybridise within genera. Genetic studies range of methods, including biological, reforestation. indicate that hybridisation is occurring chemical and mechanical controls between the many forms of Scotch broom Robust growth enables brooms to to effectively reduce the impact and that have been introduced to Australia. dominate understory and shrub spread of brooms. layers, which can lead to a less diverse understory flora and reduced over-story regeneration. Brooms form thickets that How to identify brooms The weeds impede movement and harbour feral In general, brooms have numerous, Brooms are shrubs in the pea family animals. Dense broom infestations can flexible, broom-like young branches (Fabaceae). The three WoNS broom increase the risk of fire, as well as alter that give rise to their common name. species are aggressive and capable fire regimes and soil chemistry. The three WoNS are woody shrubs of completely transforming invaded Brooms produce masses of long-lived that lack thorns and have pea-like habitats. They fix nitrogen in the soil, seeds (over 15 000 seeds per plant per pods and bright yellow flowers. Table 1 which can inhibit the growth of native year for Scotch broom) and establish large summarises the key characteristics of species accustomed to nutrient poor seed banks (over 21 000 seeds/m2 for these three brooms. soils, and create soil conditions that Scotch broom), that contribute to mass Scotch broom can be distinguished favour brooms and other weeds. germination events following disturbance. from the other brooms in Australia by Brooms grow quickly and out-compete Seeds can survive in the seed bank for more its five-sided, green stems with few, native and plantation species. They than 20 years. In favourable conditions, deciduous leaves, large flowers (to establish rapidly and re-sprout soon seedlings have high germination and 2 cm), and seed pods that are 2–7 cms after disturbances such as fire or survival success, and plants can tolerate long with obvious hairs along the forest harvests. Scotch broom can a range of habitats. Broom plants contain edges. Mature plants grow up to 4 m significantly reduce yield in forestry alkaloids that may be toxic to humans, high and have erect, sparsely-branched plantations, particularly at the beginning livestock and other animals, especially stems, which can collapse and become 2 Brooms: Scotch (Cytisus scoparius), Montpellier (Genista monspessulana) and flax-leaf (Genista linifolia) brooms prostrate in older infestations. Red (to pink) and yellow flowered varieties of Scotch broom are naturalised in Victoria and Tasmania. Montpellier broom grows up to 3m high and has erect, ridged—but not five sided—green branches that are hairy when young. The persistent leaves are on short stalks and consist of three rounded leaflets. Small yellow flowers grow in clusters along the main stems. The pods are relatively small (1–3 cm long) and covered in dense hairs. Flax-leaf broom is similar to Montpellier broom, but its leaves consist of three narrow, pointed leaflets. Leaf undersides and young stems have Scotch broom flowers and immature pods. Photo: Hillary Cherry. woolly, grey hairs, which can give plants a silvery look from a distance. Montpellier broom prefers more in the Victorian Alps and Barrington Flowers grow in dense clusters at Mediterranean climates. It flowers in Tops National Park in New South Wales. branch ends. its second year and plants can live Brooms were commonly planted in for about 10 years. Flowers appear Some native Australian plants gardens as hedges and to prevent soil in late winter or spring. Plants can can be confused with brooms, so erosion. They have spread from these flower again in late summer, under accurate identification is essential. plantings. Seeds are moved along good growing conditions. Pods ripen in Several species in the pea family, transport corridors by road graders summer and seed mainly germinates including and other equipment, and through the Viminaria juncea, Goodia in autumn, although it can germinate and dumping of garden waste. Seed is also lotifolia, Pultenaea daphnoides anytime given sufficient soil moisture species can resemble spread in soil by humans, animals and Gompholobium and temperature. Populations are one or more of the brooms. Cherry vehicles. As a result, outlier infestations persistent and can reproduce from the ballart ( ) can may establish at long distances from Exocarpus cupressiformis seed bank without disturbance. be mistaken for Scotch broom if it is not the parent plants. Disturbance, such in flower. Flax-leaf broom also flowers at two as soil movement or fire, assists years of age. Flowers are mainly broom invasion by stimulating seed produced from winter though to spring, germination. Damaged broom plants Growth cycle with fruits present in summer and seeds re-sprout readily. germinating in autumn and spring. Both Scotch broom plants first flower Montpellier and flax-leaf broom retain 2–5 years after emergence, and can their leaves year-round and, like Scotch Where they grow live for up to thirty years. Flowering broom, retain long-lived seeds in the occurs mainly in spring and early soil seed bank. Scotch broom is native to temperate summer (October to December) but Western Europe and the Canary Islands may continue until autumn in ideal region. Montpellier and flax-leaf broom conditions. Seeds ripen and shed in How they spread are native to the Mediterranean, summer to early autumn (January to including south-eastern Europe and March), and germinate in the warmer, Brooms grow from seed. Mature plants northern Africa. These brooms have wetter months. Some seeds remain can produce massive amounts of seed naturalised in many parts of the world, dormant and can survive in the soil in favourable seasons. Mature broom including North and South America, seed bank for up to twenty years if seed pods burst open in warm weather, South Africa, Asia, and New Zealand. buried. Scotch broom often loses its ejecting seeds several metres. These They have invaded over one million leaves in summer or when stressed, seeds are often further dispersed hectares in Australia, and are present but green stems enable continued through ant burial. Seed is also spread in all southern states and southeast photosynthesis. long distances by water and by a variety Queensland. They tolerate annual of animals, such as horses and sheep. rainfall of between 500–600 mm or Cattle were identified as the main more,

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