A collection of wildlife photographs

Saturday, 28 March 2015

Calcareous grassland on Therfield Heath

On 28th March, me and Miles Payling went searching for Pasqueflower Pulsatilla vulgaris. This species has a vulnerable population status and has been lost from many of its previous locations. We emerged from woodland out onto a grassland area. It was obviously calcareous, as in many places chalk was visible at the surface. Additionally it was well drained due to being on a steep bank.

Although at first they were not visible, we found Pasqueflower on a south facing slope. This perennial species has large purple flowers with six sepals (the leaves beneath the petals). The hairy stems grow to 10-30cm. The Pasqueflower leaves are deeply dissected as in many geraniums, divided into long segments, and are also hairy. Pasque means 'Paschal like' referring to the paschal full moon used to determine the date of Easter. This is relevant because the plant flowers around Easter time. 
The Pasqueflower requires short, open grassland to germinate and grown. Therefore the Rose species growing on this site in addition to others, should be managed to keep lots of light to ground level. This species is confined to just this site in Hertfordshire and is a Hertfordshire BAP species.

The calcareous grassland also supported Carline Thistle Carlina vulgaris. This species is simply a daisy with spines - quite unmistakable. It often has clusters of flowers, although the relatively young individual in the photograph below has only one flower.

Carline Thistle
Two other noteable species growing on this grassland were Salad Burnet Sanguisorba minor and Hairy Violet Viola hirsta. The leaves of Salad Burnet comprise opposite pairs of leaflets which are toothed (as shown in the centre of the photograph below). As the name suggests, the leaves of this plant are often used in salads and also smell of cucumber when bruised. Hairy Violet has suitably hairy yet also cordate (heart shaped) leaves. This violet has violet-esque five-petalled flowers, and the whole plant is covered in hairs.
Salad Burnet and Hairy Violet

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