One of the many pleasures of summer for me is that it seems to be peak time around here at least for daisies to flower. 25,000 species of daisies form the family Asteraceae, the most numerous plant family except for the wonderful orchids; nearly 10% of this number is found in Australia. Here, they are found from seashores to the top of Mt Kosciuszko, from wet forest to the driest deserts. They may be tiny annuals, perennial herbs, shrubs or trees. Apart from many popular garden plants, both ornamental and edible (artichokes and lettuce for instance) many daisies are weeds, including thistles, dandelions and boneseeds.
|Cephalipterum drummonditum in red sand plains near Mt Magnet, Western Australia.|
|Silver Snow Daisies, Celmisia sp, in mist at 1700 metres, Namadgi National Park.|
But it's the structure of the 'flower' which is one of the bases of their success. I put 'flower' in parentheses because what we see isn't really a flower at all, but a congregation of numerous flowers to increase the visibility of each to a pollinator. Here are a couple of 'basic' daisies to illustrate the point.
|Billy Button, Crapedia sp. Namadgi National Park.|
|Yellow Buttons, Chrysocephalum apiculatum.|
In each case we can see that the individual head comprises numerous tiny florets clustered together on a base which is formed by the expanded tip of the flower stalk. Each is fertile and the presence of each makes them all more visible to passing flies or wasps or bees.
Many daisies however have added refinements. A result of one such set of refinements is one of the great hoaxes of nature - a collection of little flowers to resemble a large conventional flower. Again, here are some examples.
|Podolepis jaceoides, Namadgi National Park.|
|Brachyscombe aculeata, Namadgi National Park.|
|Olearia tenuifolia, Namadgi National Park.|
In each case, we can again see the fertile disc florets in the middle; now however our attention has been drawn more strongly to them by the presence of surrounding 'petals', as in a real flower. Here however the 'petals' are themselves flowers, sterile ray florets whose sole purpose is to draw attention to the disc florets. In the second two examples, the ray florets are of contrasting colours to make the whole structure even more conspicuous.
Other daisies achieve the same effect in an entirely different way.
|Waitzia nitida, Kalbarri NP, Western Australia.|
|Xerochrysum subundulatum, Kosciuszko NP, New South Wales.|
|Leucochrysum albicans, Namadgi National Park.|
In these three cases the now-familiar central disc florets are still visible, but the attention-grabbing surrounds are formed by shiny stiff papery bracts - effectively modified leaves - either of the same or contrasting colours.
That will probably do for today, but in the not-too-distant future I'll return to the wonderful daisies, even if only to celebrate them.