Radiating

Arthonia radiata

Now that the garden has settled into its winter hibernation, I have had time to go through some of the many pictures that I took of things this past summer. And amongst them, I found this shot of a new species for the garden – the lichen Arthonia radiata. This crustose lichen (so-called because it looks like a crust, i.e. flat and inseparable from the bark) belongs to a group called the "script lichens". It gets that name due to those scribble-like black marks, which are its fruiting bodies (called apothecia). Those marks can range in shape from rounded to linear to star-like; the latter shape gives it the common name of "asterisk lichen". Each colony is surrounded by a thin dark line, which is an area of the thallus (the "body" of the lichen) that contains only fungal hyphae and no algae. The thallus itself can range from white through pale grey or fawn to brown in colour, and is sometimes partially immersed into the bark. This is a common and widespread lichen across the British Isles, growing on the bark of smooth-trunked trees and shrubs.

Lecidella elaeochroma

Lecidella eleaochroma

January is generally a quiet month for British gardens, but there are still plenty of things out there to discover. This is Lecidella eleaochroma, one of our more common lichens. Scores of them stud the trunks of many of our smooth-barked trees, often butting up against nearby colonies of Lecanora chlarotera. Where they do, a black prothallus develops along this lichen's leading edge. Like other members of the genus Lecidella, these are crustose, which means they adhere closely to the substrate upon which they grow. You couldn't get a fingernail under one; to remove it, you'd have to strip the tree's bark right off. Colonies tend to be greyer in shady spots and yellower in sunny areas, and are liberally sprinkled with round black apothecia, the fruiting bodies that contain the lichen's fungal spores. Unlike some of the other lichens I've profiled on the blog so far, this one reproduces primarily by spores, which contain only the lichen's fungal partner. This means a germinating spore must quickly find (or steal!) an algal partner – a far trickier proposition than bundling both components together in a soredium, like some lichens do. Lecidella eleaochroma is widespread across the British Isles, and indeed across all of Europe and much of North America as well.

Lecanora

Lecanora chlarotera

One of the more common lichens in our garden is the widespread Lecanora chlarotera, which grows in small, roundish colonies on the trunks of many of our smooth-barked trees. It's a crustose lichen, which means it adheres closely to the bark on which it grows, and can't be easily separated. (The yellow-orange Xanthoria parietina growing beside it, on the other hand is a foliose lichen, easily lifted with a fingernail.) The thallus of Lecanora chlarotera is creamy to grey in colour, and can be either smooth or strongly warted. Many of the colonies in our garden (like those pictured above) have been overgrown by algae, giving them a slightly greenish cast. The abundant apothecia (the lichen's fruiting bodies) are buff to reddish-brown and surrounded by a thick thallus rim. In Britain, the description of these apothecia is "like a jam tart" — that is, like a pie with a rim of crust. To give you an idea of size, the biggest apothecia shown above are 1mm across, so if you're looking at this on a computer, the picture is much larger than life-sized! As would be expected, given our location (i.e. surrounded by well-fertilised farm fields), it does well on nutrient-enriched substrates. It's one of the early colonisers of young trees in semi-urban areas, such as new plantings in car parks or housing estates.

Circles

Phaeophyscia orbicularis

With the garden sinking down into its winter rest, it's time to turn the spotlight back on the lichens that festoon some of the trees. I introduced you to the bright orange Xanthoria parietina last winter. Today, I'm focusing on the somewhat less obvious Phaeophyscia orbicularis — the variably grey species lurking beside the Xanthoria in the picture above. Like its orange neighbour, this is a foliose lichen, which means it's rather leafy in appearance. You can easily lift a corner of the lichen with a fingernail, as much of it isn't firmly attached to the substrate underneath. It can range in colour from from light to dark grey, with multiple colours often visible within the same colony. When wet, it's reported to sometimes go green, but that's not something we've seen yet.

Phaeophyscia orbicularis often forms circular colonies (plenty of examples above) which can grow up to 3 cm (about 1.25 inches) in diameter. However, it can also grow in more diffuse colonies, like the mass on the left side of the picture above. Such colonies are irregular, flatter and pressed more closely to the substrate on which they're growing. The center of the mature colonies tends to be densely covered with lumpy, dark, rounded soralia (the structures that contain little packets of fungal and algal cells that break off to form new colonies). As would be expected in a garden surrounded by well-fertilised farm fields, Phaeophyscia orbicularis tolerates nitrogen-enriched habitats. It's common and widespread across most of Great Britain (somewhat less so in Ireland), growing on bark, twigs, stone and concrete. In our garden, it's particularly common on the bigger branches of the apple trees.

Waxed paper

It's been quite a while since we've featured a lichen on the blog. This one is Parmelia sulcata, sometimes known as "Hammered Shield Lichen" or "Waxpaper Lichen" because of its appearance. Dobson's Lichens field guide says that it's "grey to glaucous white" in colour, but it always looks distinctly bluish-green to me. The brownish tips to the lobes, which are ridged and overlapping, and the network of faint, white lines along which the soralia develop are distinctive. (Soralia are the structures that hold the soredia: bundles of fungal and algal cells which break off to form new lichen colonies.) And it really does look like a bit of hammered metal. The underside is dark-brown to black and covered with a mat of rhizines, which are the fungal filaments that help to attach the lichen to its substrate.

There are quite a few colonies sprinkled around the garden, mostly on the Japanese Cherry tree and on the slowly-rotting wooden garden bench. This lichen, which is a great example of a foliose species (the name given to lichens that are flattened and leaf-like), is common species throughout much of the world. It grows abundantly on trees and rocks across most of Britain and Ireland, particularly in the lowlands. People in various parts of the world have used it to make dyes (it produces a reddish-brown colour) and medicines.

Lichen It

Funny how you can look at something regularly and still not see everything about it. I rechecked an old wooden bench in our garden that I'd already looked at multiple times and discovered a single colony of Flavoparmelia caperata growing amongst the other lichen colonies there. Given how distinctive it is, I'm surprised I didn't notice it earlier. This leafy lichen (a type called "foliose" in official lichen lingo) is a rather unique yellow-grey colour when dry (hence Flavoparmelia — flavo meaning "yellow") and a bright apple green when wet. This is a baby colony, measuring a bit less than an inch wide; at maturity, it may stretch across more than 8 inches. Its lobes are very wide (up to 1 cm or 1/2-inch) and quite wrinkly and contorted. They'll become even more so as the lichen matures. The central surface is already sprinkled with coarse soredia (lichen's way of spreading itself) even though it's a young colony. That little pink spot on the lichen's left side is a hostile fungus, one of the lichenicolous species that survives only by parasitizing a lichen.

According to Frank Dobson's seminal Lichens: An Illustrated Guide to the British and Irish Species, Flavoparmelia caperata is "very common on acid-barked deciduous trees" in the south of England. I guess old wooden benches are the next best thing! It's also found on rocks, roofs and mosses (which it overgrows). It has been badly impacted by high sulfur dioxide levels in the UK, but now that we're getting air pollution levels under better control, it's beginning to recolonize some areas where it had previously been eradicated. It's even been found on the grounds of Buckingham Palace!

The Lichen List Grows Further: Punctelia subrudecta

This speckly little gem is Punctelia subrudecta. In real life, it measures about an inch across, so this picture is considerably larger than life-sized. It's another new addition to the garden list, found while I was poking around the Japanese Cherry tree in the middle of the garden a few days ago. Lichens are certainly easier to find when the leaves are off the trees; these were on the top side of one of the bigger branches, where they'll be well-shaded for most of the growing season.

The rather flat, rounded lobes are finely sprinkled with tiny, crusty white spots called pseudocyphellae. This is where the little bundles of fungal and algal cells form soralia, which allow the lichen to propagate when they break off in wind and rain. And to think that all this time, this lichen was lurking in plain sight — just in plain sight some eight feet off the ground!

Another lichen: Diploicia canescens

So a bit of exploring today led me to a new lichen for the yard list — and since this is one I know well, I'm a little surprised that I haven't noticed it before. The grey-green lichen to the right of my thumbnail is Diploicia canescens. As you can tell from my nearby thumb, the few colonies I've found so far are pretty small; this is one of the larger ones, which probably means that these are relatively new colonists in our garden. Like the bright yellow-orange Xanthoria parietina colonies around it (see my earlier post about those), this species can tolerate quite high levels of nitrogen pollution, which is a good thing considering all of the surrounding farm fields!

Up close, you can see some of the key features of this lichen. Its color is a very pale grey-green. The lichen's lobes are convex (that is, they curve towards the branch below it) and get wider towards the tips. Unlike the neighboring Xanthoria parietina, it seldom has apothecia (the structures that carry spores). Instead, it clones itself, bundling up small numbers of algal and fungal cells (the building blocks of every lichen) in structures that look a bit like pale, yellowish flour sprinkled on the middle of the lichen. These structures break off in wind and rain, or when an animal walks across them. Now that I've been looking a bit harder, I also found some on the brick wall of our garage. How did I miss it for all of these months?!

The Lichen List: Xanthoria parietina

Now that the leaves are gone from the trees, the lichens that festoon trunks and branches are nicely visible, and I've been working to identify them. A few are easy. This is Xanthoria parietina, which is a very common species across the UK. Xanthoria means "golden-yellow" — certainly a good descriptor of this lichen, particularly when it's in a sunny spot like this, on a branch of our apple tree. In heavy shade, it's grey-green! One of the reasons that this species is so common is that it can tolerate high nitrogen and sulphur dioxide pollution, which is something that many lichens can't. And since our garden is surrounded by plenty of well-sprayed farm fields, our lichens are exposed to plenty of nitrogen. This is one of the first lichens I learned as a neophyte lichenologist, and I find it nearly everywhere I look. It's even widespread in towns and cities, particularly in areas where birds perch and poop.

Up close, you can see some of the key features that distinguish this lichen from some similar ones. The lobes at the edges of the lichen are generally flat (though sometimes turned up at the edges) and very wide — as much as 7mm (nearly a quarter of an inch) on the biggest lobes. That may not seem like much, but for a lichen, that's huge! The apothecia (those small, bright orange bits that look sort of like tiny, well-done pancakes) are numerous, relatively flat and unstalked, and clustered in the middle of the lichen. According to my lichen book, the centers of old specimens often die out, so I guess all of ours are relatively young colonies, as I have yet to find any with dead centers.