Heathland plants; (from l-r) Calluna vulgaris; Vaccinium myrtillus; Empetrum nigrum; Erica tetralix; Vaccinium vitis-idaea;
One of the advantages of living in the South Wales valleys is the access to open land and the freedom to explore. Recently I took a wander onto the ridge below the Blorenge between Blaenavon and Abergavenny
‘The southern part of this extensive upland site is comprised of sub-montane heath with large areas of Calluna – Empetrum – Vaccinium vitis-idaea, a community which is of local distribution in South Wales.’(CCW. SSSI citation)
For much of the year the dominance of the Heather Calluna vulgaris presents a somewhat dark and bleak appearance. However when you get up there and start exploring closely I quite quickly found an interesting collection of heathland plants.
Sketchbook with leaves of C vulgaris, some adpressed; some with noticeable auricles
Calluna vulgaris is abundant and still has the dried remnants of its flowers. The taller mature plants are typically dark in appearance but there are a number of younger plants that seem different at first sight. This is because some of the branches have leaves that are pressed close to the stem(adpressed) with undeveloped auricles while others are more splayed out with large noticeable auricles. The small leaves are deeply folded underneath (revolute). At the base of the branching leaf stems and flower stalks may be leaves with more pronounced auricles(paired lobes at base of leaf), also revolute.
Erica tetralix with its revolute leaf and general hairy-ness
Cross-leaved heath Erica tetralix, even in December has its dead flowers grouped near the tips of the shoots. It is noticeably hairy /downy when looked at with a hand lens and the plant is grey-green in colour. It too has strongly revolute leaves,
‘In many species, of which Calluna and Erica are good examples, the leaf margins may be folded inwards, almost meeting in the mid-line. This is an effective way of regulating water loss by transpiration in hot, dry conditions. Leaves of this type are called ericoid.'(Webb p.108)
At this site E tetralix is much less common than C vulgaris and struggles to grow through the more dominant plant.
Sketch of V myrtillus stem with solitary leaf
Bilberry or Whimberry Vaccinium myrtillus has more or less lost its leaves at this time of year and has hairless angled green stems, with alternate buds. Where the last of the leaves are hanging on these are finely toothed.
V vitis-idaea, compare with V myrtillus stem
Vaccinium vitis-idaea. Still in leaf in december
What I at first thought was A myrtillus was actually, Vaccinium vitis-idaea or Cowberry. This has evergreen leaves that are down-turned around their edges, shiny dark green on top, lighter below. It lacks the teethed edges of the V myrtillus leaf. There were still a few red berries either attached to the stems or lying on the ground beneath them.
Close up of underside of leaf of V vitis-idaea showing the downturned leaf edge and the dark hairs.
Developing fruit of Vaccinium vitis-idaea
Next up was the Crowberry Empetrum nigrum, at first glance a bit like a glossy E tetralix. Some plants still had the almost black berries still attached.
Sketch and specimen of E nigrum
Like the heathers described above, E nigrum has strongly revolute leaves. The leaves appear in whorls of 4 in the one I sketched but they are described by Rose (2006) and Streeter as alternate. Stace however describes it as whorled to spiral which is more accurate. I think that they are more alternate lower down the stem but more in whorls higher up. Noticeably less downy/hairy than E tetralix. The black berries are a give away.
Despite appearances E nigrum is not one of the Heather family (Ericaceae) but it is the sole British representative of the Empetraceae. There are 2 sub species; ssp nigrum and ssp hermaphroditum. It is difficult to tell from the samples I have but as the latter has a northern distribution it is more likely to be E nigrum ssp nigrum