Chellow Dean

Wednesday 19^th June 2019

Leader: Jesse Tregale

Starting from the car park on the south side of the B6144, we headed down the wooded valley towards the Chellow Dean reservoirs. The springtime flowers were long gone beneath the dense canopy of beech, sycamore and horse chestnut. Dog’s mercury grew alongside enchanter’s-nightshade, allowing a close comparison of these superficially similar plants, the former having gone over and the latter just coming into bloom. With houses nearby, the garden escape, box-leaved honeysuckle, grew by the track, its elongated, ridged leaves and flatter habit distinguishing it from the similar Wilson’s honeysuckle.

Emerging from the trees, we came across a large patch of common bistort to the right and someone exclaimed “dock”, a reference not to this plant’s botanical identity but rather to its use in making dock pudding, particularly in the area around Mytholmroyd in the Calder Valley. Approaching the overgrown feed to the upper reservoir, we forked right, pausing at the stepping stones, to the right of which we briefly searched, in vain, for smooth-stalked sedge, which had been seen here previously but was now presumably swamped by the lush and vigorous growth of competing plants after the past month or so of very wet weather. The attractive wood horsetail grew especially tall and wide here.

Across the stepping stones, we turned right alongside the reservoir, where giant fescue grew with hairy-brome, again allowing a contrast to be made, the former smooth with auricles at the blade/sheath junctions and the latter with hairy lower sheaths. On cleared sloping areas to the left grew unusually tall wood-sedge, benefiting from the sheltered south-facing location and plentiful rainfall. Wood melick, an attractive and occasionally-occurring grass in these habitats, was in full bloom and was also to be seen, unusually, in the wall of the lower reservoir later on. An eagle eye made out a solitary example of slender St. John’s-wort below the path.

Perhaps the plant of the evening was the cyperus sedge, growing by the water, its only known location for many of us. Botanists spend a lot of time staring down at the ground in front of them. Thankfully, someone’s concentration faltered and they pointed out white water-lilies just coming into flower on the far side of the water. Beside the path to the lower reservoir was the welcome sight of groundsel in its rayed form. I’d say that this small difference from the more common rayless form makes it a far more attractive plant; or perhaps it’s just its relative scarcity.

Taking care alongside the lower reservoir, where there was a large drop to the water, we came across a hawkweed, identified as ‘Hieracium grandidens’ by Jesse. The hawkweeds are apomictic, meaning that they produce seed without fertilisation. Well over 100 are recognised as growing in Yorkshire but, with a few exceptions, they are morphologically so similar that considerable study and experience is required to identify them correctly and it is often best to send samples to acknowledged experts.

The main attraction on the reservoir wall was rustyback, other ferns including black spleenwort, hart’s-tongue and wall-rue. On a visit in the mid-2000s, the rustyback was dominant here but spraying with weedkiller had almost eradicated the colony on our previous visit so it was gratifying to see its continuing recovery. There was some excitement over the lesser swine-cress, which grew in abundance underfoot, although some of us have yet to see the ‘ordinary’ swine-cress, which tends to grow southeast of Yorkshire.

As we crossed the dam wall, Jesse spotted lentil, definitely the unexpected find of the evening. At the far end of the dam planted trees included spindle and Turkish hazel. We turned right, heading back up the valley, coming across a large patch of three-nerved sandwort in the gathering gloom. A few colonies of hard-fern and a solitary example of perforate St. John’s-wort almost completed the species list, before dotted loosestrife brought the evening to a close.

Text by Andrew K

Photographs by Tom