In the mire

The ruins of the old lead mine workings at the top of Slitt wood, along Middlehope burn at Westgate in Weardale have a lovely flora at this time of year.

Most of the green area that you can see in the photograph above is a mire, full of moisture-loving plants and .....

..... this area, where water constantly trickles out of the mine levels and across the old lead ore washing floor is home to some interesting species. Here are a few that were at their best this morning:

Marsh lousewort Pedicularis palustris, a partial parasite on the roots of grasses.

Ragged robin Lychnis flos-cuculi

Common butterwort Pinguicula vulgaris - for more on this carnivorous plant click here 

Northern marsh orchid Dactylorhiza purpurella

Marsh horsetail Equisetum palustre spore-bearing cone

Butterwort: a botanical Jekyll and Hyde

Carnivorous butterwort Pinguicula vulgaris plants grow amongst the ruins of an old lead mine at Westgate in Weardale. This is a plant with a Jekyll and Hyde personality. On the one hand there's that rosette of sickly yellow leaves, covered in sticky mucilage, that trap and digest small insects (click here to see how they do it). Most of its prey is composed of ants and small flies.

On the other hand, it produces these charming flowers that need to be pollinated by flying insects, principally butterflies and bees. This is a plant that either eats insects or exploits them.

Butterwort blooms have a forest of short hairs in the throat of the flower. There has been a lot of speculation about their role but a plausible explanation is that they act as a barrier to insects that are too small to be effective pollinators; the hairs would steal nectar, but would offer no impediment to the long tongue of a bee or butterfly.

Butterwort isn't very common in Weardale but is more plentiful in Teesdale. Many years ago I visited a site on a small plateau on the edge of the moors where water constainly trickled over it, creating a mire full of interesting bog plants. As I looked over the edge of the plateau I saw a haze of these little mauve flowers just above the ground - there must have been many hundreds of plants in bloom. Must go back, to see if they are still there.

Wildlife in an old lead mine

Thursday's Guardian Country Diary describes some of the wildlife that has colonised the old disused lead mines at Westgate in Weardale. Many of the industrial processes that took place here (and ceased early in the 20th. century) involved the use of water, to power a hydraulic engine and to separate lighter stone from heavier lead ore (galena). The legacy is an excellent habitat for wetland wildlife which is now a Site of Special Scientific Interest.

I almost trod on this down-in-the-mouth toad, whose colour blended so well with the mosses around one of the shallow pools where it had spawned. You can see the ridge just behind its eye where the poison glands are located, which deter predators.


In this view you can see most of the main site, with Middlehope burn snaking through the valley. In the foreground you can see bridge parapets for the railway bridge that crossed the burn - ore was taken out on railway trucks pulled by horses. In the middle distance, just to the left of the third bend in the burn, you can see a rectangular depression with a pool of water in the centre. This was once a reservoir.

The reservoir is fed by water flowing out of this mine entrance, known as White's Level. The tunnel is just large enough to accommodate a small pony. Some of these mine levels stretch for miles under the hillside but are now lethal because some lead to vertical shafts where miners were winched down in baskets to tunnels that followed lead veins at lower levels in the strata.

The water flows out through a bed of watercress and into...

.... the silted up reservoir, mentioned earlier. This is a great site for dragonflies in summer, and also a breeding site for toads. The retaining wall on the left, like most of the walls of the mine ruins that were constructed from limestone blocks, is excellent habitat for ferns, like .... 



... the dainty brittle bladder fern.

These are ruins of lead mine buildings downstream, with more waterlogged ground. The key elements for plant growth - soluble nitrogen and phosphorus - are rapidly washed from the soil by rainfall and flowing water, so some of the plants that grow here are adapted to obtaining these minerals by other means.




This is marsh lousewort, a partial parasite on the roots of grasses, that connects with their root systems and siphons off their mineral supplies, and ....



.... these are plants of butterwort. Those rosettes of sickly yellow-green leaves are covered in sticky mucilage glands that trap small insects, which are then digested by enzymes secrete by the leaves.



Downstream Middlehope burn flows through the sheltered, wooded valley known as Slitt woods and ....



...... when it reaches Westgate in Weardale flows over a series of picturesque waterfalls into the river Wear.

Carnivorous Plants 1: Butterwort

If every there was a Jekyll-and-Hyde of the plant kingdom, this is surely it. At this time of year common butterwort Pinguicula vulgaris produces delightful little violet flowers that attract pollinating insects that ensure that it sets seed, while at the same time catching and digesting small insects on that rosette of sickly yellowish-green leaves down at soil level.

These plants thrive on the permanently boggy conditions on the old lead mine ore-washing floors at Middlehope Burn in Weardale. There's very little nitrogen in the ground but the small insects that they digest make up for that. The surface of the leaf is covered in glistening, stalked glands producing mucilage that glues the insect down, then tiny glands embedded in the leaf surface release diestive enzymes that convert it into nutritious soup. The rolled edges of the leaves keep the pool of digestive enzymes in place. To see the capture and digestive glands of another, more exotic butterwort species in more detail, click here. The glands release protein-digesting enzymes that curdle milk and butterwort leaves were once used in the first steps in making butter - hopefully making sure that there were no flies stuck to the leaf first!

Butterwort keeps its welcoming flowers and deadly digestive equipment well separated via a tall flower stalk...

... and the precious nectar, there to attract small bee pollinators equipped with a suitably long proboscis, lies inside that nectar spur that you can see at the back of the flower - protected by a forest of fine hairs that prevent small, non-pollinating insects from crawling in and stealing it.