Asteridea asteroides - Star-like Asteridea

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Asteridea asteroides   -   Star-like Asteridea

This exotic looking plant that you might think was a garden escapee, is in fact a WA endemic, but is rarely seen and only encountered after bushfires. It favours sand and sand/gravel soils from Geraldton (north of Perth) to Israelite Bay (east of Esperance), but is excluded from the wetter SW corner.   Locally it is rare and the few plants I have seen were in mallee heath a little north of the cleared wheatbelt farming zone, where I suspect they originally grew in greater number.

The showy white flowers are to 2.5 cm (1”) diameter, so are very eye-catching especially after fire and in the sparse early stages of regeneration. They are not regarded as rare or endangered elsewhere, so finding them in large numbers (August to November) must be quite spectacular.

To the east of Albany, there are no other native species that resemble this plant, and being so distinctive, it is unlikely to be confused with any other. However, there are three additional Asteridea species in the Esperance region, but these lack the radiating ray florets, having only tubular ones that produce a “billy-button” type flower head.

There are two similar looking species west of Albany, but both of these have smaller flowers. One is A. pulverulenta the Common Bristle Daisy, which besides the flower size, also has simple pappus bristles (not plumose), plus is largely restricted to coastal districts (Albany to Geraldton). A. gracilis the other similar looking plant is rare, and only found around Perth and the Albany districts.

Asteridea was until recently placed in the Athrixia genus, but now that only contains South African plants.  Asteridea belongs to the very large and highly diverse Asteraceae family. 

Asteridea chaetopoda – Gypsum Daisy

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Asteridea chaetopoda – Gypsum Daisy

Locally this species grows on the edge of Lake Tay (150 km or 95 miles NW of Esperance) in granulated (white sand-like) gypsum.  This gypsum formed as crystals on the vast Lake Tay claypan, which were then broken and blown by the strong, hot, prevailing northerly winds to be heaped together on its southern shores.

Asteridea chaetopoda is well protected from this harsh windblown environment by being thickly covered by matted white-woolly hair that not only reflects the suns rays, but resists the inevitable sandblasting in its exposed position, plus creates a life-saving microclimate about itself. There are few other plants that can tolerate these harsh conditions, so although being a small plant of around 10 cm in height x 30 cm diameter (4”x 12”), the Gypsum Daisy has little competition for space from larger species.

The bright yellow flowers bloom before the onset of summer (August to November), so are not subjected to the extreme conditions of its habitat. The seeds have plumed pappus attached (dandelion-like) that act as a parasol to carry it on the wind, far and wide in search of new gypsum habitat to colonise.

There are many salt-lakes in this inland region and due to their remoteness this plant probably remains undiscovered around many as is illustrated by its currently recorded wide and scattered distribution. Asteridea chaetopoda is found from the Meekatharra region (700 km or 450 miles NE of Perth) to the Kalgoorlie region (560 km or 350 miles ENE of Perth), with outlying collections NE and SW of there. It has also been collected from the western edge of the Nullarbor, then jumps across most of the Esperance region to reappear at Lake Tay and further west in the Lake Grace district.

Australian plants in the Asteridea genus were previously listed under Athrixia, which is still current in South Africa, whilst both belong to the Asteraceae (Daisy) family.

Asteridea archeri – Gypsum Daisy

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Asteridea archeri – Gypsum Daisy

Asteridea is part of the giant worldwide Asteraceae (daisy) family, but Asteridea archeri is known only from a gypsum/saltlake complex 145 km (90 miles) NE of Esperance. Here scattered on extensive samphire flats (plant community of succulent salt-tolerant plants), are island-like mounds of gypsum to 10 metres (over 30’) in height,  comprised of a very fine powdered gypsum soil, on which this small daisy makes its home. When you walk on these mounds, you sink to your ankles and leave footprints that last for many months until the gypsum slowly expands to leave a smaller depression. However, wildhorses commonly pass through this area and can make quite a mess.

In this very harsh, windswept, low rainfall environment and incredibly dry powdery soil, the sub-shrub Asteridea archeri, grows in colonies mostly on the eastern and southerly slopes. One of the photos above shows the environment, with the small dark tufts being the daisy. It grows to 150 mm (6") in height and apart from the flowers is covered in fine woolly hairs, which probably provides insulation from high summer temperatures, plus creates a more favourable micro environment. As very few other plant species survive here, it is good testament to its effectiveness.

The flowers are white and neatly arranged into compact heads. However, the time they flower is highly dependent on rainfall and varies considerably from June to October and probably either side of these months if conditions are suitable. Since the discovery of this daisy in 1990, gypsum-mining has commenced on one of these mounds.  At this stage the plants are not endangered as mining activities are limited, but if conditions change and extraction increases, the habitat of this species will be severely compromised.

Asteridea athrixioides – Wirewort

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Asteridea athrixioides – Wirewort

Asteridea belongs to the huge Asteraceae family that are commonly known as Daisy Flowers, but some may know them from Compositae, although the former is gaining greater acceptance. Even the Asteridea genus is newly (1980) adopted, having previously been known as Athrixia. These name changes are not uncommon with such a large worldwide family and the varying opinions of many taxonomists.

Asteridea athrixioides is a pretty brightly coloured yellow daisy that is also known as ‘Wirewort’ because of the wire-like flower stems (wort, an old English name for plant). It is mostly an inland species being found over 500 km (300 miles) from the coast, although locally it can be seen to the North and NE of Esperance, around saltlakes and low granite outcrops, generally in the heavier sandy loams.

The composite flowers are made up of many small tubular florets, which are held tightly together by numerous thin hairy bracts. The 2-4 pappus bristles (the fluffy parts of dandelion flowers that float on the wind) have long plumose hairs only on their ends, probably requiring a strong wind to carry them any distance, but as suitable habitat is usually not very widespread, there is probably little need.

The flowers are around 1.5 cm (½”) diameter and are recorded from July to November, but in this extensive dry inland environment, rainfall would very much determine their occurrence and around Esperance, between August and October being more likely.