Thursday, 30 June 2011

Knowing your umbels

It has been a soggy June north of the border, following on from one of the wettest Mays on record. Parts of west Scotland recorded rainfall levels of 250% the monthly average. Watching news coverage of parched earth and stunted cereal crops in East Anglia it is sometimes hard to credit we live in the same small isle. On the plus side, nothing grows without rain and it has been a season of rampant growth. Hedgerows, meadows and lanes are ablaze with wild flowers and it is hardly possible to go for a country walk without wading through a strangle of brambles and nettles and tall stems of hogweed with its profusion of white and pinkish flowers.

The unkindly named hogweed is a member of the carrot family, a very large group of mostly white or yellow flowering plants which includes many important culinary species like chervil, cicely, caraway and angelica and others with medicinal properties. Many of them grow to a great size, none more so than hogweed which often reaches shoulder height. The giant hogweed, not native to Britain although widespread here, may tower to ten feet or more.

Typical flat topped umbel of common hogweed
Like most of the carrot family, common hogweed or Heracleum sphondylium bears its small flowers in spoked clusters called umbels (think umbrella). These may be the breadth of a hand span and are typically flat topped and borne high about the stout hollow stems. For novices like myself telling umbelliferous plants apart can be confusing as they may be very variable and the individual flowers are often indistinct. Usually the shapes of the leaves give better clues and fortunately they often grow together, making for easier comparison.

And identification is important, for mixed in among these aromatic herbs and also bearing white umbels are some of the most poisonous plants to be found anywhere, the hemlocks and water dropworts, which are potentially lethal to humans and livestock alike even in comparatively small doses. Some of them are all the more dangerous for being common and all parts of the plants are toxic; leaves, seeds and especially roots. Hemlock poisoning, which causes respiratory paralysis while still conscious, was apparently a favoured means of execution in classical Greece. Its most celebrated victim was Socrates, put to death for his outspoken criticism of Athenian democracy, whose demise is told of by Plato in the Phaedo.

Outermost flowers of each cluster are larger
Common hogweed isn't poisonous, nor is it something you would probably want to try to eat, but it does have a taxonomic name with classical associations, Heracleum. I wonder whether this is simply a reference to its size or whether like Achillea, the yarrow - which Greg wrote so interestingly about- there is some other significance that I am missing.

It is fairly straightforward to identify from the flowers alone. They are often pink when still buds, the ones in the centre of each umbel being the last to open. There are five petals and flowers at the outer edges of the cluster have a pair of larger petals, projecting outwards, shaped rather like miniature fish tails. The flowers are much frequented by insects including bees. They give off a mildly unpleasant scent which I have only really noticed on hot, muggy days when the flowers are very abundant. Hogweed's attraction of insects potentially makes it a valuable companion plant for crops because it may aid pollination or pest control. Certainly it is often found around field edges but I think it unlikely that its seeds have been sown purposely as it is naturally invasive.

I don't suppose hogweed will feature high on the list of favourite wild flowers for many people and I must count myself among them. But I associate it with countless country walks on summer days when the sky is blue and the air is hot and fizzing with insects. And in our current, decidedly unspectacular Scottish summer, that surely can't be bad.


  1. I'm reading all about umbels on a beautiful summer evening. What a lovely post. Full of images of summer. I want to go for a country walk now I know my umbels.

  2. I have been reading lots of horror stories about giant hogweed, Heracleum mantegazzianum, which contains a virulent sap that reacts with ultraviolet light to cause terrible skin burns that may leave permanent scarring or photosensitivity. People using strimmers or clearing the invasive plant are advised to wear protective clothing, gloves and goggles, but even those brushing innocently againt broken stems may develop rashes and burns. The results look really nasty. Fortunately this does not apply to our common native hogweed.