Hollas Bridge and Ryeburn Reservoir

Saturday 29th September 2018

Leader: Steve Hindle

14 of us met at this site next to the river Calder, just south of Halifax, in lovely, sunny weather. We set off to the first site for the species that was our main objective for the day, Autumn Crocus (Crocus nudiflorus), through a strip of woodland by the river. We came across a small group of flowers by the side of the path, but Steve then showed us a much larger stand under the trees, by the side playing fields. These beautiful flowers were in full bloom. It was remarked that the flower stems were longer here than in other, more open areas, possibly because the plants were ‘reaching up’ for the light. There had been an even larger stand in the playing fields themselves, but Steve explained that this had been destroyed by the fields being mowed.

Steve explained how the Autumn Crocus may have been introduced to this area. It is thought that they were originally introduced from the Pyrenees by the Knights of St John, the Knights Hospitallers. This order of Knights owned a lot of land in the Calderdale area and many of the crocus colonies are found on this land. They were introduced to produce a dye similar to saffron, which the Knights would have used in their healing duties and to make a dye for textiles. Autumn Crocus would have grown have grown better in the hay meadows of this area than Saffron Crocus (Crocus sativus) itself would have.

True to form, the Group then spent some time investigating a large car park. Most of the species here were planted, but some were very attractive, such as Virginia-creeper (Parthenocissus quinquefolia), with its beautiful display of red leaves. There was also Himalayan Birch (a cultivar of Betula utilis var. jacquemontii), a commonly planted tree which has entirely and intensely white bark. There was also extensive patches of Chinese Bramble (Rubus tricolor), which also had attractive leaves with varying amounts of dark red on them and, in an area of rough grass at the side of the car park, a patch of entirely white-flowered Wild Radish (Raphanus raphanistrun ssp raphanistrum), some flowers of which had purple veins.

We then proceeded to the canal (the Calder and Hebble Navigation) for a brief look around. Here, Rustyback (Asplenium ceterach), Maidenhair Spleenwort (A. trichomanes), Wall Rue (A. ruta-muraria) and a Polypody (Polypodium sp.) were seen on one short stretch of wall.

We collected our lunches from the cars and continued onto an area of rough grassland near to a flood water storage channel. On the way, we saw Spreading Hedge-parsley (Torilis arvensis). This is most easily distinguished from Upright Hedge-parsley (Torilis japonica) by the fruits. The fruits of Spreading Hedge-parsley have straight spines which are minutely hooked at the end, whereas those of Upright Hedge-parsley have spines which are curved, but not hooked at the end.

In the grassland itself, we saw Wild Clary (Salvia verbenaca) and Alsike Clover (Trifolium hybridum). The latter species is told apart from White Clover (Trifolium repens) by the fact that the shoot doesn’t root at the nodes, which means it is possible to lift the shoot up vertically from the ground.

We then drove a short way to another site for the Autumn Crocus, where there was a fairly large patch of plants in bloom under trees in a field.

The final site of the day was Ryeburn Reservoir, near Ripponden. We were hoping to see Shoreweed (Littorella uniflora), but weren’t successful in finding that species. We did, however, see a good number of other ‘draw-down zone’ species, such as Red Goosefoot (Chenopodium rubrum), Amphibious Bistort (Persicaria amphibian), Water Pepper (P. hydropiper), Marsh Cudweed (Gnaphalium uliginosum), Purple-loosestrife (Lythraceae salicaria) and Toad Rush (Juncus bufonius). Some of these species were present in large numbers as extensive stands. We also saw Trailing Tormentil (Potentilla anglica) and the subspecies of Greater Plantain with much shorter spikes (Plantago major ssp. intermedia).

The weather and the beautiful displays of Autumn Crocus made this a hugely enjoyable day and a great way to end the field botany season.