Ancient woodlands provide a rich and unique community of plants and animals, as they have been around long enough for the ecosystems to develop into complex and irreplacable habitats. Plants and animals depend on the stable habitat the woodland provides due to the relatively undisturbed soils. Ancient woodland is any woodland that has been around since 1600AD (1750AD in Scotland) or earlier; some woodland in the UK has been around since the last Ice Age approximately 10,000 years ago! 1600 was when planting of new woodland became more common and so woodland established before this time is likely to have developed naturally.
They also indicate to us signs of history that allow us to trace backwards throughout the woodland's lifetime, giving them cultural value as well as conservational. Medieval boundary banks, old coppice stools - all tell a story about an England very different to the one we now know. Ancient woodland can be characterised as
Semi-natural woodland: Mainly made up of trees and shrubs native to the site, arising from natural generation in most cases.
or
Plantations on ancient woodland sites: Areas of ancient woodland where the former native tree cover has been felled and replaced by planted trees, typically not native to the area. Planted Ancient Woodland Sites (PAWS) can be restored to give rise to Restored Native Woodland on Ancient Sites (RNWAS).
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| Foxley Wood: Photo by Richard Osbourne |
Foxley Wood is Norfolk's last remaining ancient woodland, and it contains a number of ancient woodland indicator species (AWI's), including:
Wood anemone (Anemone nemorosa)
Wood sorrel (Oxalis acetosella)
Honeysuckle (Lonicera peliclymenum)
Common dog violet (Viola riviniana)
Dog's Mercury (Mercurialis perennis): A case study
Kingdom: Plantae
Family: Euphorbiaceae
Species: Mercurialis perennis
Dog Mercury: Photos from naturessecretlarder.co.uk
The name 'dog's mercury' is said to originate from the messenger of the gods, Mercury, who is the one to discover it. 'Perennis' is used to distinguish it from the 'annua' species, which was used as a diuretic (to increase urine production) and as a purgative (to give a laxative effect). 'Dog's' is a term used to describe a plant with no medicinal uses (in the sense of 'false' or 'bad', as even though recently it has been harvested to use as a laxative this is discouraged by herbalists due to its cumulative effect.
Dog's mercury can quickly colonise and spread throughout an area by using underground rhizomes. The plant favours alkaline soils and is found in abundance in suitable habitats in limestone regions. It is present in neutral soils too, but not acidic soil. This can lead to crowding out of other, rarer, species such as Fly orchids, or even Ash seedlings, which we saw are already under threat due to Ash dieback diseases, present on some of the trees in Foxley Wood. The plant is characterised by its spear-shaped, toothed fresh green leaves, upright set, small, greenish flowers, and a foul and rotten smell that it produces. By coppicing at Foxley Wood, the woodland floor is exposed to sunlight which helps other flowers and plants to thrive and thus keeping others that spread easily under control: preventing the Dog's Mercury takeover. In other areas of East Anglia where coppicing as ceased, Dog's Mercury has been observed to be increasing in abundance.
Dog's mercury is highly poisonous, due to the combination of methyl amine trimethylamine, a volatile oil and saonins. It is diuretic purgative, and emetic, meaning it causes diarrhoea and vomiting after consumption. Larger doses also lead to lethargy, jaundice, painful urination, gastric and kidney inflammation, inflammation of the cheeks and jaw, and potentially a coma which leads to death. Yep, that's enough to keep me well away.
The leaves often poison sheep or cattle, but no incident of severe human poisoning has been reported since the 1980s when a couple ate the plant after boiling it, thinking it to be a green vegetable: they recovered within 2 days. The first case of human poisoning was reported in 1693, when a family of five ate it and one of the children died. For some reason though, some people still think it's worth a try! One woman wrote on 09/02/17 when commenting on a blog about Dog's Mercury: "I picked some dog mercury and ate it on a salad. I thought I'd read a small amount was ok to eat... was enough to cause my lips, mouth and throat to burn. This was followed by a feeling of shaky weakness and a need for the toilet".
Why you would want to risk it I do not know, but I guess it goes to show that you should double check if something is safe before you try eating it! All in all, this is a pretty nasty plant from anyone's point of view. So by all means, look out for it the next time you think you might be in an ancient woodland, as well as the other AWI's, but don't get too close!
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