Tuesday, June 5, 2007

Groundsel Senecio vulgaris

I am an amateur naturalist trying to learn something about everything that lives in my garden.

Growing in my garden behind my house - at (0.1,1.5), see here - I found the weed seen in photo 1 (click on it to enlarge). A quick look in a wildflower book and the curiously compact yellow flower heads (the flowers are fully mature in the photo, not unopened as a first glance might suggest) enabled me to easily identify it as Groundsel, Senecio vulgaris. The form of the flower head is what botanists term " a rayless capitula" (a capitula being the term for a head composed of many indiviual, bunched flowers -dandelion heads are another example).

According to my copy of The Englishman's Flora (Geoffrey Grigson, Paladin, 1975), the word groundsel derives from the Old English grunde-swilage: literally 'ground swallower' - a reference to the plant's ability to rapidly colonise newly cultivated soil. The Latin name Senecio, is thought to come from senex meaning 'old man' - a reference to the plant's white head of 'hair' (the seeds) which over time fall out exposing a little bald white head! A charming analogy I'm sure you'll agree.

Although groundsel does find mention in herbal medicine (Culpepper mentions its use in inducing sweats and as a purgative), in common with other members of the daisy family, it contains numerous unpleasant chemical compounds and is best regarded as highly poisonous to humans. The black-and-gold striped caterpillars of the Cinnabar moth are very fond of it however.

A search of the internet led me to the discovery that my humble weed has quite a degree of fame in the scientific community: In 2003 botanists Dr's Abbott and Lowe published a scientific paper describing a weed that Dr. Abbott had found growing wild at the edge of a car park in York twelve years previously. The paper showed that the plant was a fertile cross between groundsel and another British plant, Oxford Ragwort. This made it only the sixth new species of plant to have been discovered in Europe and North America in the last century. More remarkably still, since this new species was believed to be less than 50years old, finding it marked not just the discovery but the very emergence of a wholly new living species within our lifetime! (See this article for some colour photos).

Oxford Ragwort has its own marvellous story incidentally, having been introduced from Sicily to Oxford University's botanic gardens in 1690, whence botanists recorded its systematic spread over much of the UK over the next two hundred years. Being a plant indigenous to the cinder-strewn volcanic slopes of Sicily, it was aided in its march by the emergence of a network of cinder strewn railway lines in Britain at the time.

Some of you may recall that in a previous posting I wondered whether a careful study of a magnified view of a dandelion seed would allow you to tell apart the 235 sub-species of dandelion. I still don't know the answer, but certainly the seeds of groundsel (photo 2 - click to enlarge) and dandelions are quite different, with the pappus (the 'feathery bit') connecting directly onto the achene (the seed body) in groundsel, whilst for dandelions (or the one I found at least) the two were separated by a thin stem.

The knowledge of groundsel's importance in evolutionary biology and its charming image as a little old man, left me with rather a soft spot for my humble weed. Unfortunately, as you will shortly read, this little old man was not in the best of health...

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