Olearia lacinifolia (family Asteraceae) are found in the treed inland mallee region from Mt Ragged to Lake Grace. It is generally found on gentle slopes and hollows in the deeper sandy loams. It grows to a little over 1 metre (4') in height with an open structure. The flowers are white or pale pink with a yellow centre and grow to 4cm (1+3/4") diameter. The unusual and distinctive leaves are strongly toothed but not prickly, they have glandular hairs and are therefore slightly viscid and odorous, but not unpleasantly so. Flowering is very much influenced by weather conditions and although most flowering is during winter/spring, this timing is variable with blossom comonly found outside this range during cool periods after rainfall. A dainty little, not well known, little flower:
Olearia muelleri is widely distributed across Australia, especially in the dry mallee country of Australia. In Western Australia it is very common in the Goldfields region and across the Nullarbor. It is a very hardy species being able to tolerate very hot and dry conditions. The flowers are over 2cm (to 1") diameter, a vivid white with a yellow centre. although blue/purple colours are also recorded. Flowering takes place anytime from August to January although, in fickle and low rainfall areas, weather conditions will play a large part in the timing. You can see from the photograph the type of harsh conditions where these plants live. I certainly wouldn't want to live where they are. Far too hot for me.
Olearia ramossissima is restricted in Western Australia to inland mallee regions, where they are widespread, even occurring on the Nullarbor. This much-branched daisy bush can grow to over 1 metre (4'5") but is usually much smaller, particularly in harsh conditions. The leaves are ideally suited to the dry inland, being less than 2mm in length and like most vegetative parts, are covered in fine woolly hairs, features highly effective in reducing moisture loss in a 30-40cm (12"-14") average annual rainfall range. Flowers can be white, blue, purple and pink, and vary in size from 1-1.5cm (1/2") diameter. Once again you can see how dry it is in the areas where these flowers grow.
I had to add this little charmer? "Why?" you ask. 'Cos it's yellow of course.
Ornduffia parnassifolia is a very common herbaceous plant with the flowering stem growing to 60cm (2") in height and can produce dozens of hairy 2cm (3/4") diameter sunny yellow flowers over a considerable period. It is mostly found on the outer edges of swampy areas, including heavy seepage zones and even along roadsides that have deep gutters where rainwater collects. The seed is thought to be spread by water birds, particularly ducks, which visit most pondage areas along the south coast of Western Australia during winter/spring. It can flower at any time of the year providing there is sun and moisture and does not mind being partly inundated for several weeks. It is a marsh plant rather than a true aquatic. It can also survive quite well in better drained soils, although then flowering is usually restricted to spring and early summer when seasonal conditions are warm and rainfall higher.
Sincere thanks to "Esperance Wildflowers" for the above information (much of which I have condensed) and the beautiful photographs.