Secrets of the daisy family
There is one wild flower that everyone recognises without fail – the humble daisy. But even this plant, which is part of one of the most prolific and colourful floral families, isn't all it seems…
There are at least one hundred native and hundreds more introduced species of the daisy family – or Compositae – making it one of the largest families in our flora. It is also one of the most conspicuous families and includes the familiar daisies, ragworts, groundsels, thistles, dandelions, coltsfoot and a host of other, similar plants.
When something is so common or garden it is easy to wrongly assume that what you see is what you get, and there is nothing interesting to learn about these little weeds. You would be wrong. There is more than meets the eye of this family - actually they lead a life of deception and showy half truth.
The common daisy is probably the best known, and is instantly recognisable. Its name, daisy, is a contraction of its old name ‘day’s eye’ – so called because in full sunshine it opens wide but as the light fades the petals close like sleepy eyes. In gloomy weather all you will see is the pink-tinged ‘bud’.
The flower hides an interesting secret that not many people will realise… It is not actually a flower at all…
Anyone who has played ‘he loves me, he loves me not’, pulling the petals off a daisy, might have noticed that its ‘flower’ is different from that of, say, the winter aconite or the barren strawberry. Under a magnifying glass you can see that each daisy ‘flower’ is not one single flower at all but many separate flowers on a dome at the top of the stem.
Each head has about 150 flowers of two quite distinctive kinds: there are about 100 disc (yellow) flowers clustered in the centre and about 50 spreading (white) ray flowers. Both kinds of flower bear seeds, but only the disc flowers produce pollen.
The whole daisy head resembles a single flower and functions like one too. It opens, attracts insects by offering pollen and nectar, becomes pollinated and withers as its seeds ripen. It is the compound head of flowers, which functions as though it were one flower, that basically characterises the daisy family.
The daisy blooms in profusion in spring to late autumn, and even in mid-winter you may see a few flowers on sunny days. Its ability to survive both winter rain and frosts, and summer dryness and heat accounts for some of its success as a weed. Also the daisy has all its leaves and buds at ground level and its flower head grows on a leafless stem; so as soon as lawn mower crops off one daisy head, there is another bud ready to shoot up and burst into flower.
Coltsfoot too are conspicuous as their bright yellow ray flowers spread open in the sun. They look rather like small dandelions until you notice their pinkish stems. They appear in March before their broad leaves have grown. Indeed, by the time the leaves develop the ‘flowers’ have been replaced by feathery ‘seed heads’ that are dispersed by the slightest puff of wind.
Oxford ragwort, despite its name, is not native to Britain; it probably originated from Sicily where it grows high up on the larva-strewn slopes of Mount Etna. It escaped from the Botanic Garden at Oxford towards the end of the 18th century – that’s where it gets its name from! With the coming of the railways, its plumed seeds were sucked behind trains along the cinder tracks which provided them with similar habitat to their native volcanic slopes.
Now Oxford ragwort is a common weed that brightens up many industrial areas with its all-yellow flowers, as well as popping up at the bottom of walls and fences (it particularly likes old walls for some reason). It has even ‘fathered’ a new and exclusive British species, the Welsh ragwort.
The Welsh ragwort’s other parent was the groundsel. These two species crossed earlier this century in Wales, with a specimen dating back to 1925 having been found . Hybrids between species are usually sterile and would be expected to die without leaving offspring. However, by chance this hybrid was fertile and its descendants survive, recognisably different from both of their parents – and interestingly, not able to cross breed with them. They are effectively a newly-formed species. Welsh ragwort is still relatively rare. It is a particularly interesting plant to botanists because it is new, native, and exclusive – very few plants or animals are restricted to Britain.
Groundsel is a common weed that scarcely stops blooming in sheltered sites, even in the middle of winter. Its flowering heads are neither obvious nor flower-like because they lack the cluster of bright yellow ray flowers you find in most composites. Instead their minute yellow flowers or florets are packed into tight heads, each about 5mm in diameter and surrounded by black-tipped bracts, and the flower heads are grouped into loose clusters at the top of stems.
The ‘flowers’ come into their own when they burst open into the distinctive dandelion clock of thousands of seeds, which are carried off by the wind. The plants make an excellent vegetable for pet birds and rabbits in winter.
With its misleading flowers masquerading as a single bloom, and creation of a new species unique to Britain, the daisy family really is leading a life of secrets and deception. Long may it continue to intrigue us.
Related to the daisy is another great weed success story, the dandelion. They are one of our most successful and conspicuous composites. Since their feathery fruits, each containing a single seed, are widely dispersed on the wind, dandelions colonise recently cleared ground and, once established, their deep, long-lived and exceptionally tough roots help them to survive all but the most determined efforts by man to remove them. Even a small piece of root left in the ground can regenerate a whole plant within a very few weeks, easily defying a casual gardener.
There are more than 200 types of dandelion and they grow in a variety of habitats ranging from wet marshes to dry chalky grasslands. They reproduce asexually. The seed embryos are not fertilised by insect pollination (as they are in many other types of lower). Confusingly, however, pollination is often required for the development of the seeds, and this happens when dandelions attract nectar-seeking insects.
The reproductive processes are complex. The pollen is usually sterile and the whole flowering effort from March to June, when countless millions of yellow heads brighten the countryside, seems like one vast charade: an ostentatious display of colour that is by no means necessary for its survival. Each seed is an exact replica of those of the parent plant, and they remain identical through many generations. A new type of dandelion only develops as a result of a mutation – a rare and accidental change in the genetic composition of a plant so that all its offspring are slightly different from their parents.
Oxford Ragwort (Senecio squalidus), right, with an ageing Peacock butterfly drinking its nectar. Ragwort flowers from April - December, approx. Prolific in England and Wales, it is rarer in Ireland and Scotland.
The close up of a daisy flowerhead, left, clearly shows the bright yellow florets that are actually tiny, individual tubular flowers, along with the ray florets we think of as petals.