Cassop Vale, April 2021

The regular snow showers which punctuated our fieldwork in the Lakes and sub-zero night time temperatures should have warned me that we’re not finished with winter just yet!  Last Monday, Sue and I set off up the hill to Cassop though a covering of fresh snow, which lasted most of the day on sheltered, north-facing slopes.  When I went again with Martyn, on Sunday, it was warm enough to be walking in T shirts!

Our first real find day was spikes of Blue moor-grass, Sesleria caerulea, sticking up through the snow on Monday on the sides of the cutting above the vale itself.  We assumed at first we were seeing last year’s seed heads but their fresh metallic purple-blue colour is unmistakable.

Sesleria caerulea

Blue moor-grass is one of the earliest grasses to flower each year and is restricted to fairly limited areas of limestone grassland in the north of England, though it’s also found on sandy loams over micaceous schists in Perthshire. 

A treat lay in store as we dropped down through the woodland into the valley – Wood anemones now carpet the ground and Woodruff and Bluebell leaves show what is to come.  The woodland is certainly old, whether or not it is formally ‘ancient’.  In England, tree cover needs to have persisted since 1600 to be designated ancient woodland and, as this area was part of the hunting park of the Prince Bishops of Durham, that’s certainly possible.  There have been settlements in the area since long before the Prince Bishops arrived and the trees have clearly been coppiced in the past so this, as in most parts of the north-east, is semi-natural woodland rather than ‘wildwood’.

Wood anemone, Anemone nemorosa, is a good indicator of old woodland because it grows and spreads so slowly, by way of underground rhizomes.

Anemone nemorosa

According to Plantlife, it spreads no more than a couple of metres in 100 years.  Coppicing the trees under which it grows helps it to flourish by reducing the trees’ vigour and giving the anemone more time in the light for growth, before being cast into deep shade as the canopy fills out.  We are lucky to have many areas of old woodland around Durham which are carpeted with these delicate flowers at the moment. The white ‘petals’ of the flowers are actually sepals, with tiny flowers in the centre of the bowl they form.  Like the Lesser celandines I talked about last month, anemones are ‘primitive’ flowers, members of the buttercup family.  I’m embarrassed to say I’ve only just realised that the flowers can have anything from six to eight delicate sepals.  

The cows were still in the reserve on Monday but, by the time we went on Sunday, they have been shut into the field at the far end of the pond.  The vegetation should start to grow more vigorously now, at least once the snow goes for good.  I’d promised Sue banks of Primulas, but these were mostly under snow when we visited.  By Sunday it was apparent they are mostly Cowslips rather than Primroses.  Worryingly the trampled ground around the pond is thickly covered with Himalayan balsam seedlings – the cows don’t seem to be have been very effective in keeping those in check. 

Cowslip, Primula veris, and Himalayan balsam seedling

Happier finds amongst the close-cropped turf include tiny Common whitlow-grass, Erophila verna, an alien-looking strobilis of Field horsetail, Equisetum arvense, releasing clouds of spores and my first stunted Hawkweed of the year (a Hieracium, but I’m not even going to attempt the species!).

Clockwise from top left: Hawkweed, Horsetail, and Common whitlowgrass

I have a soft spot for horsetails, though many regard them as invasive weeds.  How can you not love something which has survived more or less unchanged for more than 300 million years, when tree-sized horsetails dominated Earth’s vegetation during the Carboniferous period?  The fertile strobili, produced at this time of year, are followed by sterile green photosynthetic shoots, later in the year, whose whorls of narrow leaves give the plant its common name.   

One of my hopes for this year’s exploration of Cassop is to see another ancient so-called ‘fern ally’, Adder’s-tongue fern, Ophioglossum.  I’ve seen this in upper Weardale and on Tunstall Hill in Sunderland, of all places, but it has not been recorded here since 1969 so finding it here would be something of a coup – it is not easy to spot….

Ophioglossum vulgatum

The woodland area of the reserve along the old wagonway sits under a lovely cloud of Blackthorn blossom at the moment and there are little pockets of Dog violets nestling against many of the tree trunks. 

Onwards and upwards.  My May trip(s) to Cassop beckon and relaxing of the Covid lockdown rules means I can go there with more than one of my botanical buddies at a time.  What will we find now that the cows have done their job?

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