Oxfordshire: Green Hound's-tongue near Pyrton

13 June 2012                                    OS map 171 Chiltern Hills West

Length: 30 mins.

Green Hound’s-tongue Cynoglossum germanicum is a native Rare Data Book species protected under Schedule 8 of the Wildlife and Countryside Act 1981.  It grows only in a very few localities in Gloucestershire, Oxfordshire and Surrey.  In Oxfordshire it is probably now limited to a single site.

          We parked in the centre of the village of Pyrton SU688958.  The origin of this name is the Anglo-Saxon pirige tun “settlement with pear-trees”, presumably indicating that it was once notable for its pear orchards, so a secondary aim of our visit was to see if we could see any remnant wild pears (although none are recorded for this area on NBN Gateway or in the Oxfordshire Flora).  We walked north up the road (Knightsbridge Lane).  We were immediately struck by the proliferation of hedgerow crane’s-bill Geranium pyrenaicum in the road verge, able to compete in places with tall vegetation of nettles. 

Hedgerow crane’s-bill

Keeping an eye open for fruit trees, we saw a medlar Mespilus germanica overhanging from a garden.

Medlar

Outside the village the hedgerows were prolific with other fruit trees like wild plum Prunus domestica and escaped apples Malus pumila, but no ancient crab apples and no wild pears of any kind. On reaching a lane on the right to Knightsbridge Farm we reached a copse extending both sides of the road, rather like a very wide hedgerow, marked by old banks and wide ditches, apparently an ancient feature. 

Knightsbridge Lane through copse

This is the site for green hound’s-tongue and there was no problem in finding it, as it grows through most of this copse, which extends for about a third of a kilometre up the road.  It grows in large congregations within the copse and along the edge beside the road, although some of the latter plants were distorted by what looked like the effects of chemical spray presumably used to control roadside vegetation.  Surely it must be illegal for the council to spray a Schedule 8 plant?  However, the general population was unaffected and they thrived here in their thousands.

          It is quite distinct from the usual hound’s-tongue Cynoglossum officinale in being very green.  The flower-stalks in seed spread out very long and almost horizontally from the top of the stem giving it a very distinct appearance, making it easy to spot from a distance. 

Green hound’s-tongue: general form

The seeds were similar spiny nuts grouped in fours, but with no marginal flange like the common species. 

Green hound’s-tongue fruits

Most of the plants by the time of our visit were in seed with a few last small reddish flowers at the end of each stalk.  It blooms, like other Boraginaceae, by gradually maturing and uncoiling from the base. 

Green hound’s-tongue early flowers

A few plants in the shadiest spots were only just coming into flower and lacked the jizz of the plants with long fruiting-stalks. 

Green hound’s-tongue coming into flower

Like its common relative, green hound’s-tongue is biennial and there were numerous clumps of large dark green leaves, reminiscent of dock or foxglove that will produce next year’s flowering stems, by which time the larger first-year leaves will have died away. 

Red14 Green hound’s-tongue with old oak

(first year rosette of large leaves to left)

Large blotch leaf-mines were evident on quite a few plants, the effect of the larvae of the fly Agromyza abiens, which mines many different species of Boraginaceae.

Mine of Agromyza abiens in green hound’s-tongue leaf

Apart from the prevalence of green hound’s-tongue, which seemed to be able to hold its own with other tall plants like stinging nettle Urtica dioica (although it did not seem to grow in the grassier parts dominated by false brome Brachypodium sylvaticum), the copse was quite unexceptional in its flora, with, apart from nettle, much cow parsley Anthriscus sylvestris, herb-robert Geranium robertianum and ground ivy Glechoma hederacea.  A few species like dogwood Cornus sanguinea, traveller’s joy Clematis vitalba and spindle Euonymus europaeus, plus some woodruff Galium odoratum, indicated a degree of calcareous influence, but the surface soil was basically clay. 

Spindle with cranefly Nephrotoma guestfalica

(leaf-edge gall at top caused by mite Stenacis convolvens)

There were several large trees, especially oak and ash, indicating that this woodland had existed for several hundred years at least.  Elm shrubs are difficult to name, but they included some small-leaved elm Ulmus minor with frequent “pimples” on the leaves, the galls of the mite Aceria campestricola.  There were frequent dog-roses in flower Rosa canina (some the form with conical discs) and one specimen with downy leaves (some bi-serrate), bi-pinnate sepals and a few glands that appeared to be Rosa x dumetorum, the hybrid between R. canina and R. obtusifolia Round-leaved Dog-rose.

Dog-rose

On our way back we took a diversion to a wood across a field just to the west of this copse, as the most likely site to which the green hound’s-tongue might have spread, but we could not see any specimens near the edge.  Rampant growth of bramble and bracken in places may have not been conducive to its establishment.  Given that the hound’s-tongue has been known from the copse for a considerable time it remains a mystery why it has not spread beyond there, its seeds easily being able to grip fur or feathers and so, we thought, capable of being transported – they were even able to grip the skin of our fingers.  The limitation may be the lack of suitable habitat, although it is not obvious exactly what conditions it requires.