Asteraceae

DICOTYLEDONS

ASTERACEAE - Daisy Family

A very large, worldwide family of mainly shrubs and herbs, but sometimes trees. The flowers (florets) are small, but are usually grouped together in an inflorescence (called a head) which gives the appearance of being a single flower and led to the family's earlier name of Compositae. There are two types of florets. Disc florets have very small lobes, ray florets have longer ones, expanded to resemble a single petal. For accurate identification it is often necessary to use a microscope to study the details of the arrangement of the florets in the head, and the shape of the fruit and the pappus, the tuft of fine hairs or bristles at the top of the seed. This may enlarge into a hooked or feathery parachute for seed dispersal. Consult a specialist text, or an expert, for more help. There are probably around 20,000 species in the daisy family worldwide, many of economic importance. There are around 500 species in Western Australia, of which some 110 are naturalised.

Acanthospermum hispidum (starburr) is an erect, sticky-hairy annual up to 50cm tall. It has stalkless, ovate leaves with tiny flower heads in their axils. The fruits develop into a star-shaped prickly burr that causes problems if caught in wool. Found in disturbed ground in the Kimberley, and possibly elsewhere in Western Australia. Flowers in summer and originates from South America.

Acanthospermum hispidum, GK

Achillea millefolium (yarrow) is a perennial, spreading by rhizomes. It forms a patch of upright, feathery-looking leaves which, in spring, give rise to flowering stems 40cm tall. The heads are small, with white or pink ray florets, grouped into flat-topped clusters. A strong-smelling plant, brought from Europe to be planted in herb gardens, it has been found on wasteland and road verges in the Perth, Pemberton and Esperance areas.

Ambrosia (ragweeds) are weeds of disturbed areas around Perth, introduced from North America. The greenish yellow flower heads contain disc florets only, the male ones nodding in a terminal spike, the females upright, singly in the axils of the uppermost leaves.
A. artemisiifolia (annual ragweed) is a tall, branching annual to 1m, with angled, often reddish stems and greyish, fern-like divided leaves. It flowers in autumn, and is found on roadsides and wasteland.

Ambrosia artemisiifolia , RR

A. psilostachya (perennial ragweed) is a clump-forming perennial, increasing by rhizomes, that flowers in late summer. It is found on waste ground around settlements in the south-west. Both plants are reputed to cause hay fever and contact dermatitis.

A. psilostachya, RR

Arctotheca is a southern African genus of four species, two of which are found in Western Australia. A. calendula (capeweed) is a major weed of crops and pastures. It is an abundant plant, found in all habitats throughout the south-west, often dominating pastures, and increasing rapidly in the arid zone, where it is displacing everlastings. It is a rosette-forming annual, with greyish, lobed leaves, hairy-white on the underside, and heads up to 6cm across, produced in spring. They have brilliant yellow ray florets and a centre of black disc florets. The seeds are covered in a beige fluffy 'wool'.

Arctotheca calendula , JD

A. populifolia (dune arctotheca) grows on foredunes from Perth to Esperance. It forms a dense perennial clump with ovate, grey, fleshy leaves. The flowers, produced from winter through spring to early summer, are about 3cm across and both disc and ray florets are golden yellow.

A. populifolia , RR

Arctotis stoechadifolia (arctotis) is often planted in gardens or as a coastal sand stabilising plant. It is a prostrate perennial, rooting at the nodes, with grey, divided leaves and heads up to 10cm across. The ray florets are usually white but can be cream, pink or bronze and are produced from late spring to early summer. A native of South Africa, it is spreading from plantings and dumped garden rubbish between Jurien Bay and Busselton.

Arctotis stoechadifolia , PH

Asteraceae continued

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*Acanthospermum hispidum* (starburr) is an erect, sticky-hairy annual up to 50cm tall. It has stalkless, ovate leaves with tiny flower heads in their axils. The fruits develop into a star-shaped prickly burr that causes problems if caught in wool. Found in disturbed ground in the Kimberley, and possibly elsewhere in Western Australia. Flowers in summer and originates from South America.	*Acanthospermum hispidum, GK*
*Achillea millefolium* (yarrow) is a perennial, spreading by rhizomes. It forms a patch of upright, feathery-looking leaves which, in spring, give rise to flowering stems 40cm tall. The heads are small, with white or pink ray florets, grouped into flat-topped clusters. A strong-smelling plant, brought from Europe to be planted in herb gardens, it has been found on wasteland and road verges in the Perth, Pemberton and Esperance areas.
*Ambrosia* (ragweeds) are weeds of disturbed areas around Perth, introduced from North America. The greenish yellow flower heads contain disc florets only, the male ones nodding in a terminal spike, the females upright, singly in the axils of the uppermost leaves. *A. artemisiifolia* (annual ragweed) is a tall, branching annual to 1m, with angled, often reddish stems and greyish, fern-like divided leaves. It flowers in autumn, and is found on roadsides and wasteland.	*Ambrosia* *artemisiifolia* , RR
*A. psilostachya* (perennial ragweed) is a clump-forming perennial, increasing by rhizomes, that flowers in late summer. It is found on waste ground around settlements in the south-west. Both plants are reputed to cause hay fever and contact dermatitis.	*A. psilostachya*, RR
*Arctotheca* is a southern African genus of four species, two of which are found in Western Australia. *A. calendula* (capeweed) is a major weed of crops and pastures. It is an abundant plant, found in all habitats throughout the south-west, often dominating pastures, and increasing rapidly in the arid zone, where it is displacing everlastings. It is a rosette-forming annual, with greyish, lobed leaves, hairy-white on the underside, and heads up to 6cm across, produced in spring. They have brilliant yellow ray florets and a centre of black disc florets. The seeds are covered in a beige fluffy 'wool'.	*Arctotheca* *calendula* , JD
*A. populifolia* (dune arctotheca) grows on foredunes from Perth to Esperance. It forms a dense perennial clump with ovate, grey, fleshy leaves. The flowers, produced from winter through spring to early summer, are about 3cm across and both disc and ray florets are golden yellow.	*A. populifolia* , RR
*Arctotis stoechadifolia* (arctotis) is often planted in gardens or as a coastal sand stabilising plant. It is a prostrate perennial, rooting at the nodes, with grey, divided leaves and heads up to 10cm across. The ray florets are usually white but can be cream, pink or bronze and are produced from late spring to early summer. A native of South Africa, it is spreading from plantings and dumped garden rubbish between Jurien Bay and Busselton.	*Arctotis stoechadifolia* , PH