Broom

Cytisus scoparius (L.) Link ssp. scoparius

Synonyms - Sarothamnus scoparius, Spartium scoparius.

Family: Fabaceae

Names:

Cytisus Is from the Greek kytisos and was the name of a fodder plant that was probably Medicago arborea.
Scoparius is from the Latin scopa meaning broom or scoparius meaning sweeping and refers to its use for making brooms.
Broom refers to its Latin name and its use for making brooms.

Other Names:

Common Broom
English Broom refers to its country of origin.
Scotch Broom refers to its country of origin.
Scottish Broom refers to its country of origin.
Spanish Broom (USA)

Summary:

An upright to drooping, woody, many branched, perennial leguminous, deciduous, almost leafless shrub up to 3 m tall with a profusion of golden yellow, pea type flowers in spring. The young branches are have 5 green, hairy ridges. Older branches are tan with few hairs and no distinct ridges.

Description:

Cotyledons:

Two.

First leaves:

Leaves:

Usually has three leaflets (trifoliate) but may be single on young growth. Single or in clusters at the nodes. Alternate.
Often fall off leaving the plant almost leafless.
Stipules - Minute or absent.
Petiole - Obvious and short on lower leaves but may be very short on young leaves. Leaflets stalkless.
Blade of leaflet - Entire, egg to lance shaped. Centre leaflet 5-20 mm long x 1.5-8 mm wide and side leaflets smaller. Smooth on the upper surface, silky underneath. Hairy.

Stems:

Woody, brownish-green, flexible, 5 ribbed. Silky hairy when young becoming hairless with age. Many straight, ribbed, semi erect branches. Up to 3000 mm tall but more usually 1200-2000 mm tall.

Flower head:

Single or in pairs in the axil of bracts or small leaves usually towards the ends of the stems.

Flowers:

Large, 16-25 mm long, pea type and usually yellow or partly to all red. There may be other colours in garden varieties. Shortly (5-8 mm) stalked.
Ovary - Sessile. Several ovules
Style - long, hairy and spirally coiled.
Calyx - 5-6 mm long, broadly bell shaped. 2 lipped. Upper lip has 2 tiny teeth. Lower lip has 3 tiny teeth. Persistent in fruit.
Petals - Yellow. Standard is broad and recurved and 16-20 mm long x 20 mm wide. Keel obtuse, bent downwards.
Stamens - United
Anthers -

Fruit:

Initially green then brown or black, flattened, explosive pod with 6-22 seeds. 25-60 mm long x 10-12 mm wide. Pod remains coiled on the bush after the seeds have been released. Hairy along the joins or margins.

Seeds:

Yellow-brown, shiny, rounded and flattened, 3-4 mm long x 2 mm wide.
The seeds have a fleshy yellowish appendage (aril).

Roots:

Stout and often branched taproot.

Key Characters:

Trifoliate leaves.
Leaflets entire.
Flowers are pea type, yellow and in loose leafy racemes
Calyx green, shortly 2 lipped, teeth minute.
Style coiled into a circle.
Stamens 10, united. Staminal tube completely closed around the ovary.
Anthers not bearded.
Seeds in pods.
Seeds carunculate (with a fleshy appendage)
Adapted from John Black, Gwen Harden.

Biology:

Life cycle:

Perennial hedge plant.
Seeds germinate in autumn and spring and grow slowly in their first year. In their second and subsequent seasons they flower in spring to early summer and the pods develop over summer. On hot days the pods burst open noisily, catapulting the seeds several metres. A second flowering may occur during summer. Leaves often fall during summer and the plant remains relatively leafless for most of the year until new leaves are produced in late spring. Plants probably live for 10-15 years.

Physiology:

Fixes nitrogen with rhizobia bacteria in the root nodules.
Cold tolerant.
Tolerates low P and N levels but responds readily to phosphate fertilisers.
Tolerates shade and will establish in 90% shade.

Reproduction:

By seed.

Flowering times:

August to November in South Australia.
Spring in NSW
September to April in New Zealand.

Seed Biology and Germination:

Seeds are long lived.

Vegetative Propagules:

Will regrow from the root crown

Hybrids:

Commercially available Brooms in a range of flower colours are available from nurseries. These are all derived from a brown and yellow variety found in France in 1844 and named Cytisus andraenus or a cross of this species with Spanish Broom (Cytisus multiflorus) and called Cytisus dallimorei. The garden varieties are therefore all forms or hybrids of the weedy Broom (Cytisus scoparius) and should be carefully monitored for weediness.

Allelopathy:

Population Dynamics and Dispersal:

Spread by seed a few metres per year. Most long distance spread is by floods, machinery and in agricultural produce. Road making is a major source of spread.
Broom produces large amounts of seed and seedlings establish readily in disturbed sites. It rarely invades undisturbed bush but is invasive where the bush has been thinned by man or disease or disturbed by pigs or rabbits. Once established it smothers shrubby understorey species and prevents the establishment of most native species.
It often invades areas where Blackberry has been controlled.

Origin and History:

Europe, Mediterranean, Russia, Asia Minor, Azores, North Africa.
Introduced as an ornamental and soil stabiliser.
Probably introduced into NSW before 1801.
Naturalised in Victoria by 1887 and declared a noxious weed in 1901.
Broom was adopted as the floral emblem of Henry II of England and was known as Planta genista and provided the name "Plantagenet" for the royal family that ruled England for 300 years. This name lives on in Shire of Plantagenet in South West of WA.

Distribution:

ACT, NSW, NT, QLD, SA, TAS, VIC, WA.
New Zealand, North America, South Africa, India, Iran, Spain, Portugal.

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Moderate to high rainfall areas.

Soil:

Prefers creeks and gullies or low fertility areas often on steep slopes. Mainly on slightly acid soils and rarely on alkaline soils.

Plant Associations:

Grass lands, shrub lands and open forests.

Significance:

Beneficial:

Ornamental. Shelter. Hedge plant. Used to stabilise dunes.
In India it is used as a nurse plant in forestry to protect seedling trees from frost and wind.
Used for tanning, a source of yellow dye.
An extract from the twigs is used in herbal medicine.
Branches are used for brooms and thatch.
The bark has been used for rope.

Detrimental:

Invasive weed of disturbed areas, orchards and pastures.
Interferes with reafforestation and often overruns forests after harvesting.
Flammable and carries fire to the tree tops in forest situations.
Very competitive displacing native and other desirable species, especially in nitrogen deficient areas.
Provides harbour for feral pigs and other vertebrate pests.
Invasive weed of the USA infesting over a million hectares.
In the Northern hemisphere, superstitious societies believed bad luck befell those who brought the flowers indoors in May.

Toxicity:

The seeds are suspected of being toxic if eaten in quantity. In the USA the foliage causes digestive disorders in horses.

Symptoms:

Treatment:

Remove stock from the infestation if toxicity suspected.

Legislation:

Noxious weed of NSW, SA, TAS, VIC and New Zealand.

Management and Control:

Slash or cut close to the ground during the dry season (In the wet season most plants will regrow from the rootstock after cutting). Cultivation after slashing is also used but this provides a good seed bed for the establishment of seedlings which must be controlled. Introduce stock to eat seedlings or cultivate again. Spray with Garlon® or Grazon after flowering and before pod set when the plants have maximum leaf coverage.
Glyphosate, fluroxypyr and metsulfuron have given good results in trials.

Thresholds:

Eradication strategies:

Apply a mixture of 1 part Access® (or Garlon®) in 60 parts diesel as a band to the lower 30 cm of stems just after flowering. Burn the area after the mature plants have died to help reduce the seed bank. Burn again 2 and 4 years later. If burning is not an option remove seedlings by hand pulling, slashing or spraying with Garlon® or Grazon. Seedlings will emerge for at least 5 years.
For isolated plants, use a weed wrench that pulls up the roots, mark the area and remove seedlings for at least 5 years.
For isolated plants where it is difficult to return to control seedlings, spray the plant and a 10 m area around the plant with a mixture of 1 litre of Grazon plus 250 mL Pulse® Penetrant in 100 litres of water. The soil residual chemical will help control future seedlings.
Individual plants can be manually removed and burnt before seeding.
Dense patches have been controlled by bulldozing then disc cultivation as required over a two year period.

Herbicide resistance:

None reported.

Biological Control:

Several biocontrol agents have been released in the USA, New Zealand and Australia without resounding success. These have included a stem mining moth (Leucotpera spartifoliella) and a seed eating beetle (Apion fuscirostre).

Related plants:

White Spanish Broom (Cytisus multiflorus) has smaller (8-12 mm) white flowers flecked with purple, grey green thinner stems

Plants of similar appearance:

Flax-leaved Broom (Genista linifolia) has narrower leaflets that are rolled on the edges and retained all year. Its yellow flowers are smaller than Broom flowers.
Gorse (Ulex europaeus) has darker flowers, flowers earlier and is very spiny. Its leaves are spine like and only has trifoliate leaves on the seedlings.
Montpellier Broom (Genista monspessulana) has smaller (9-13 mm) yellow flowers, bigger teeth on the calyx and the style is short and incurved. It is usually hairy with many trifoliate leaves.
Spiny Broom (Calycotome spinosa) is spiny.
Spanish Broom (Spartium junceum) has larger (20-30 mm) fragrant flowers with one lobe, the calyx has 5 small teeth and split to the base on the upper side, anthers are bearded at the base and the stems usually leafless. Ornamental.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P166. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P450.

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P524. Diagram.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #323.3.

Parsons, W.T. and Cuthbertson, E.G. (1992) Noxious weeds of Australia. (Inkata Press, Melbourne). P469-472. Photos.

Randall, J.M. and Marinelli, J. (1996) Invasive Plants. (Brooklyn Botanic Gardens Inc. Brooklyn). P52. Photo.

Roy, B., Popay, I., Champion, P., James, T. and Rahman, A. (1998). An Illustrated Guide to Common Weeds of New Zealand. (New Zealand Plant Protection Society). P140. Photo

Stucky, J.M. (1981). Identifying Seedling and Mature Weeds Common in the Southeastern United States. (The North Carolina Agricultural Research Service and The North Carolina Agricultural Extension Service, North Carolina State University, Raleigh).

Wilding, J.L., Barnett, A.G. and Amor, R.L. (1987). Crop weeds. (Inkata Press, Melbourne).

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.