As always at this time of year, life seems to get in the way of blogging but today’s heat has encouraged me to stay in and get writing! The forecast was so good yesterday that staying at home wasn’t an option. We headed for our favourite loop in Upper Teesdale; down the road from Cow Green reservoir towards Langdon Beck, across Widdybank pasture to join the Pennine Way, up the River Tees to Cauldron Snout, then back along the east side of the reservoir. What a difference from our last visit in March (see What do Upper Teesdale and Ladakh have in common?).
Apart from the wall-to-wall sunshine, the other big difference was the number of plants in flower, many of which I’ve not seen there before. I realised that, though we walk this loop several times a year, we don’t often visit in June. Drawn by Spring gentians and Bird’s eye primrose in May, it’s often later in the summer before we visit again.
Gentiana verna (left) and Primula farinosa (right)
Now I know what we’ve been missing! The hay meadows near Widdy Bank Farm are at their glorious best now, just like Hannah’s Meadow, further down the valley, a couple of weeks ago.
One of today’s pleasures was noticing new plants – Yellow saxifrage, Early and Northern marsh orchids, Louseworts and two of the UK’s indigenous insectivorous plants – Sundew and Butterwort.
Dactylorhiza incarnata (left) and Saxifraga azoides (right)
It’s no coincidence that many of the plants we saw today need a little help to survive in this not- always-hospitable environment. Cold, damp conditions for much of the year mean that mineral nutrients are recycled only slowly and often limit plant growth.
Louseworts are hemiparasitic plants, like the Yellow rattle often included in ‘wild flower meadow’ seed mixes – in fact Pedicularis palustris is also known as Red rattle.
Pedicularis sylvatica (left) and P. palustris (right)
We may see the presence of lousewort as a good thing, for ecosystem diversity; Kris Decleer and colleagues (Decleer et al., 2013) show how P. palustris can be used as an ‘Ecosystem engineer’ for restoring wetland meadows because it parasitizes sedges, reducing their ability to dominate the ecosystem. However the common name is a clue to the fact that it has not always been so welcome. According to Geoffrey Grigson in The Englishman’s Flora, the plant was supposed, somehow, to give cattle liver flukes!
Butterwort and Sundew take things even further to obtain the nutrients they need. Stalked glands on Butterwort leaves secrete mucilage to which small insects are attracted and then stick. Once the insects are firmly held, the leaf curls inwards and the insects are slowly broken down into a nutritious soup by enzymes secreted by glands on the surface of the leaf itself. The released nutrients are then absorbed by these same pores. Maybe because of its unusual eating habits, Butterwort has long been ascribed magical properties according to Geoffrey Grigson. Butterwort, applied to a cow’s udders, was supposed to ward off evil and protect the milk and butter they produced.
Butterwort – Pinguicula vulgaris
It’s easy to see where both the common and scientific names for Sundew come from – ‘drosos’ is the Greek word for a dewdrop. Although they look rather different, with more obviously adapted leaves covered in much longer, mucilage-covered tentacles, Sundews have a very similar strategy for carnivory. Their tentacles attract and entangle prey and curl around it to hold an insect in place whilst enzymes turn it into soup which, in turn, is absorbed by glands on the leaf surface. The tentacles are sensitive to touch and will respond by curling around the prey within a matter of seconds, making sure it is in contact with as many stalked glands as possible to speed up the process.
Both Butterwort and Sundew have one obvious problem to contend with – they rely on insects for pollination so must, somehow, ensure they don’t eat species which do this. It seems that they use a range of visual, spatial, and chemical signals to spare flower visitors while trapping prey insects (El-Sayed, et al., 2016). Some carnivorous plant species have leaves and flowers which produce different blends of volatile organic compounds to attract and repel specific insects, others rely on the colour of the flowers to attract pollinators or a long stalk to separate the flower from the hazard posed by the leaves.
Sundew – Drosera rotundifolia
Like Butterwort, Sundew has an air of mystique about it, partly because of the way the ‘dew’ hangs around on its leaves. From the earliest times, plants for medicinal or magic use have been picked before the dew evaporates for greatest efficacy, so there is clearly something special going on here. In The Haven of Health (1548), Thomas Cogan gives a recipe for a liquor called Ros Solis, distilled from Sundew along with herbs and spices, which is supposed to have had potent aphrodisiac and strengthening powers and might explain why he referred to the plant as ‘Youthwort’.
Perhaps the most unexpected thing I found out about Sundew, when reading around a bit today, is that the nanofibers and nanoparticles which make up the elastic, sticky mucilage which catches insects might have important medical applications. When dried, the mucilage provides a substrate to which living cells can attach and so could potentially be used to coat surgical implants or organs for transplant, increasing the rate of a patient’s recovery and reducing the potential risk of rejection. The mucilage can also stretch to nearly a million times its original size, giving it real potential for wound treatment and regenerative medicine (Zhang et al., 2010).
Today’s walk was a salutary reminder of what we can miss by always visiting a place at the same time of year!
Decleer K., Bonte D. & Van Diggelen R. (2013) The hemiparasite Pedicularis palustris: ‘Ecosystem engineer’ for fen-meadow restoration. Journal for Nature Conservation, 21, 65-71.
El-Sayed A.M. et al. (2016) Pollinator-prey conflicts in carnivorous plants: When flower and trap properties mean life or death. Sci. Rep. 6, 21065; doi: 10.1038/srep21065
Zhang M. et al. (2010). Nanofibers and nanoparticles from the insect capturing adhesive of the Sundew (Drosera) for cell attachment. Journal of Nanobiotechnology, 8, 20; doi:10.1186/1477-3155-8-20