Golden rod

Solidago altissima syn. Solidago canadensis
Herb
Alternate
Simple
Yellow
Green

This is a rhizomatous, spreading, somewhat weedy plant that can rapidly colonize an area by creeping rhizomes and self-seeding. 

Common names 
Also known as: American goldenrod, Canada goldenrod, common golden-rod, golden rod, tall goldenrod,
Family 
Asteraceae
Deciduous 
No
Flowering time 
Summer
Native/Exotic 
Exotic
Origin 
Native to eastern Canada and eastern USA.
Notifiable 
No
State declaration 
Nil
Council declaration 
Class E - Early detection and eradication
Known distribution 

Widely naturalised in southern and eastern Australia (i.e. in the coastal districts of Queensland, in some parts of central and northern New South Wales, in south-eastern South Australia, and in the coastal districts of south-western, north-western and southern Western Australia).

Also naturalised on Lord Howe Island and sparingly naturalised in Victoria.

Habitat 

In its native range in North America golden rod is often a weedy component of vegetation in abandoned pastures and roadsides, in abandoned fields, grasslands, forest edges and humandisturbed habitats in urban areas and settlements (Walck et al. 1999). Often the abandoned sites are colonised rapidly after abandonment. 

Habit 

This goldenrod is 0.5–2.0 meters tall, and is among the tallest of goldenrods, hence its common name. The stem is rigid and generally smooth.

Impact and control methods 

It is a strong competitor in part to alleleopathic compounds (chemicals that suppress the growth of other plants) it produces and in the garden and grasslands, it can become weedy. Introduced to Europe and Asia, it has become a serious weed in those locales

Stem and leaves 

Leaves are alternate and are 6.4–8.9 centimeters long by 1–2 centimeters wide. The underside of the leaves is covered in thin stiff hairs. 

Flowers and fruits 

Heads are generally borne individually or in clusters of two or three, and are found at the top of the plant. Each head generally has five ray flowers that are 2–3 millimeters long, and numerous disk flowers. Both the ray and disk flowers are yellow. The entire head is 7–8 millimeters wide. One plant can produce as many as 1500 small yellow flower heads in a large conical array.

Reproduction and dispersal 

Goldenrod reproduces from seed and from creeping rhizomes.  Individual clones are long lived and can reach an age of 100 years. Reproduction occurs every year, but individual shoots remain vegetative if too small. Plants are able to reproduce in their first year under good conditions.

The small-size seeds are essential for long-distance dispersal and colonisation. Achenes released 1 m above the ground in winds of up to 5 m/s had a peak modal dispersal distance of 0.3 m, a mean of 0.6 m and a maximum of 2.4 m. Short-distance dispersal is possible by rhizomes. Locally the population increase is mainly a result of clonal growth.