Identification can (it is said) be “a challenge” … nevertheless, this lichen is found all over the continent; widespread and common. Usually on bark, more rarely on rock. This is a pioneer species that is frequently found on twigs and limbs.
Foliose, lobes without marginal cilia (though sometimes with rhizines projecting from the undersurface, lobe surfaces ± smooth or with faint white flecks (pseudocyphellae), centre of thallus often warted, a rather untidy look to the whole thallus, soralia absent; apothecia with brown to black, thinly pruinose discs, margins regular to somewhat irregular with small, swollen warts or lobes. Locally on twigs and bark, predominantly in the north and west.
Rock Greenshield Lichen (Flavoparmelia baltimorensis)
Found on a glacial moraine boulder – a medium to large foliose lichen with a yellow green upper surface when dry; lobes rounded without pseudocyphellae; the upper surface with globose, pustule-like growths resembling isidia. Lower surface is black with a narrow brown zone at the margins.
Mainly eastern US distribution; common wherever exposed acidic rocks are present, especially horizontal or sloping surfaces, it is less common on vertical surfaces. This species was formerly lumped with P. caperata.
The golden colour calls to the eye. Probably a species I will need to return to later in the year when its growth should be more “helpful”. To quote form an expert – “This micro-beauty usually appears in discrete, suborbicular, flat cushions, which are quite small, less than 10 mm in diameter. But, it can be also be abundant, in larger, irregular, widespread fragments, sometimes confluent and covering the whole small branches circumferentially. When looked through a hand lens it is an incredible natural filigree of golden lobes set in a delicate and stochastic ornament. The lobes are attached to the bark with scattered, white, simple rhizines.“ The yellow pigment provides a “sunscreen” for the algae that dwell in this species and grow better in low light levels. One of the more common tree lichens.
Common Greenshield Lichen (Flavoparmelia caperata)
A medium to large foliose lichen that has a very distinctive pale yellow green upper cortex when dry – and it was certainly dry on this winter’s day. It is found on a wide range of surfaces and may grow to cover an area the size of a dinner plate – it was certainly the commonest lichen seen in the woodland we were visiting. Its name comes from ‘flavus’ in Latin, which means yellow or golden. This may be a little misleading as its colour is mostly an apple green.
I noticed that Tom (who “invented” the 1000 Species challenge) has spent increasing amounts of time with lichens recently. I had thought to skirt around these as they are, like Gulls, known to be difficult. However, when out birding in a wooded area we happened upon this rather splendid antler-form species and then started spotting them all over the place. Hence the next three days are going to going to be devoted to lichens – which are very interesting things. Note – identifying lichens in winter is not the ideal time as reproductive structures are not exactly evident … must return in spring and summer and look for more.
Note: I puzzled for a long time over the identity of this lichen. It is VERY similar to Oak Moss Lichen (Evernia prunastri) which exists all over the northern hemisphere, mostly on the bark of oak trees but also on firs and pines and a few others. In France it is harvested for fragrant compounds used in perfumes. An expert on iNaturualist confirmed that it is E. mesomorpha … good to know. Apparently what we have here is an immature thallus. Soredia are not delimited in patches as in E. prunastri and smaller branches are not flattened.