flax-leaf broom

Genista linifolia
Shrub
Alternate
Compound
Yellow
Green

An evergreen shrub growing to 3 m high consisting of one main stem with many brownish green branches above. Leaflets are dark green in colour
narrow (10–25 mm long) and slender (1–4 mm wide with rolled edges) with pointed ends and are arranged in groups of 3 leaflets along the branch. The under-side is densely covered in fine hairs giving a silvery appearance.

Common names 
Also known as: flax broom, flax-leaf broom, flaxleaf broom, Mediterranean broom,
Family 
Fabaceae
Deciduous 
No
Flowering time 
Spring
Native/Exotic 
Exotic
Origin 
Western Mediterranean region
Notifiable 
No
State declaration 
Category 3 - Must not be distributed or disposed. This means it must not be released into the environment unless the distribution or disposal is authorised in a regulation or under a permit.
Council declaration 
As per State Declaration
Known distribution 

This species is widely naturalised in the temperate regions of southern Australia. It is most common and widespread in Victoria, south-eastern South Australia, and the central and southern parts of New South Wales. Also naturalised in Tasmania and becoming more widespread in south-western Western Australia.

Habitat 

A weed of roadsides, railway lines, gardens, drains, fence lines, disturbed sites, waste areas, waterways, grasslands, open woodlands and pastures that is mainly found in temperate regions.

Habit 

An upright (i.e. erect) and spreading shrub usually growing 1-2.5 m tall, but occasionally reaching up to 3 m in height.

Impact and control methods 

Flax-leaf broom (Genista linifolia) is a significant environmental weed in Victoria and South Australia, a minor environmental weed in Tasmania, and a "sleeper weed" in other parts of southern Australia. It is also listed as a priority environmental weed in at least one Natural Resource Management region. Infestations of this species shade and crowd out smaller shrubs and groundcover species, eventually dominating the shrub layer of woodlands and severely impeding overstorey regeneration. Flax-leaf broom (Genista linifolia) grows in a variety of natural habitats including forest margins, open woodlands, grasslands and riparian areas. It prefers slightly acidic soils in warmer temperate regions with moderately high rainfall. Being a legume it fixes nitrogen, which can increase soil fertility and encourage other weeds to invade infested areas.

Stem and leaves 

The younger stems are greenish in colour, ridged lengthwise (i.e. longitudinally), and densely hairy (i.e. pubescent). Older stems turn brownish-green or grey in colour and become woody as they mature.
The leaves are alternately arranged, stalkless (i.e. sessile) or almost stalkless (i.e. sub-sessile), and consist of three narrow (i.e. linear to lanceolate) leaflets. These leaflets (10-30 mm long and 0.5-5 mm wide) have shortly-pointed tips (i.e. mucronate apices) and margins that are rolled downwards (i.e. they are revolute). Their upper surfaces are dark green and hairless (i.e. glabrous) or slightly hairy (i.e. sparsely pubescent), while their undersides are paler green and densely hairy (i.e. appressed pubescent).

Flowers and fruits 

The bright yellow flowers are pea-shaped and borne on short stalks (i.e. pedicels) 2-4 mm long. These flowers (10-15 mm long) are very numerous and borne in short dense clusters (containing 3-16 flowers) at the ends of the branches (i.e. in terminal racemes). They have five green sepals (6-9 mm long) that are partially fused together at the base into a short tube (i.e. calyx tube). The uppermost petal (i.e. standard) is larger than the two side petals (i.e. lateral or wing petals), and the two lower petals are fused together into a single entity (i.e. a keel) and are folded lengthwise. Flowering occurs mostly during spring.
The fruit is a silky or downy (i.e. pubescent) pod that turns from green to grey or black in colour as it matures. These pods (13-30 mm long) are somewhat rounded in cross-section (i.e. terete) and usually contain two or three (sometimes up to six) brown or greenish-brown seeds. These seeds are rounded (i.e. globose) to rectangular in shape (2-3 mm across) and have an orange structure (i.e. aril) attached to them.

Reproduction and dispersal 

This species reproduces only by seed. These seeds are dispersed short distances (up to 3 m) when they are ejected from the mature pods. Longer distance dispersal can occur via vehicles, machinery, water, birds and other animals, and also in contaminated agricultural produce, soil and dumped garden waste.

Similar species 

Flax-leaf broom (Genista linifolia) is similar to Cape broom (Genista monspessulana), Madeira broom (Genista stenopetala), broom (Cytisus scoparius subsp. scoparius), spiny broom (Calicotome spinosa), Spanish broom (Spartium junceum) and gorse (Ulex europaeus) at a distance.