22-Mar London’s Wild Green Wonders

On old walls, some long-rooted spleenworts have new leaves pushing through their old tattered ones. On the walls of Lesnes Abbey, the maidenhair spleenwort Asplenium trichomanes, black spleenwort A. adiantum-nigrum and wall rue spleenwort A. ruta muraria can all be found and six other wild ferns in the woods nearby. Other, rarer wild species in London, such as polypody Polypodium vulgare and shield ferns Polystichum spp. are also producing their spores. Both these ferns used to be in Epping Forest, but now only the latter remains.

The giant among British wild ferns is the Royal fern Osmunda regalis which now exists mainly in gardens, and a few wild places such as Wimbledon Common. At this time of year we can see its greenish pink croziers with their reddish bloom. The common horsetail Equisetum arvense is also producing its strange looking fertile fronds among its non-fertile fronds. Its new growth can look like a miniature bright green coniferous forest. There are five more horsetails, but these are rarer. The edges of ponds, wet woods, cemeteries and railway embankments are good places to look for them.

Mosses

The sporangia of another common moss already seen, the greater matted thread moss Bryum capillare, are now bright green and distinctly plump. Small, round, hoary cushions of moss on the tops of walls are very common now and often include the grey cushion moss Grimmia pulvinata which can produce its fruiting bodies at any time of year. Another species which stands out now, but is not producing spores, is the silvery thread moss B. argenteum. The bright days of March tend to dry the moss out, giving it a distinctly silvery appearance. This is due to the fine, long, glass-like tips of its leaves, best seen through a hand lens. This moss is sometimes seen on the rubber surround of old car windows, where it looks like shiny fur.

Hampstead heath is a good place to start getting to know mosses and liverworts in a little more detail. Of the seventy-five mosses recorded there most of London’s most common mosses are present along with the more common genera such as 2 Hair mosses (Polytrichum spp.), 4 Bog mosses (Sphagnum spp.), 7 Thread mosses (Bryum spp.), 2 Screw mosses (Tortula spp.), 3 Feather mosses (Brachythecium spp.) 5 Bristle mosses (Orthotrichum spp.), 3 Pocket mosses (Fissidens spp.) and 8 Beard mosses (Barbula spp.).

Similarly, among the fifteen liverworts on the heath there is an excellent range of their various different growth forms. For instance, the Overleaf Pellia (Pellia epiphylla) with its unusual pale-stalked spore capsules and the Crescent-cup liverwort (Lunularea cruciata) with its odd crescent-shaped cups already mentioned in February. However, there are others such as the Creeping Fingerwort (Lepidozia reptans) which has finger-like growth, the Forked Veilwort (Metzgeria furcata) which looks more like miniature seaweed. The Bifid Crestwort (Lophocolea bidentata) which has unusually pointed leaves and the Common Pouchwort (Calypogeia fissa) whose leaves are very round and beautifully overlapped. The Dilated Scalewort (Frullania dilatata) even has leaves the shape of urns which can contain live pond animals and the Inflated Notchwort (Gymnocolea inflata) belongs to that small group of plants that are almost black in colour.

Lichens

As a group they are difficult to identify but if you note their size, colour and the amount of powder or scales covering them it can help in making a field identification. It is the species with bright signal red tips to their fruiting bodies (the cups) that always get noticed first, so much so some have even been given some English names such as Bengal matches, Devil’s matches or British soldiers. The latter presumably referring to the colour of historical uniforms. In this group Cladonia polydactyla var. polydactyla is probably the most likely to be found. It is variable but usually has branched greyish green vertical stems finishing in bright red tips. Not all the tips are red and few end in cups. It likes growing on damp logs in the wetter parts of woods where it is often growing with C. coniocraea which is similar but more worm-like and with no red tips. Together they can form extensive mats covering logs or the bases of trees.

The areas of heathland on Hayes Common are a good place to look for the next two species. C. floerkeana is similar to matches, just having what looks like a drop of bright red sealing wax on the tip of each of its stems. C. macilenta is taller with smaller red drops on its tips, no cups and tends to be more bluish in colour.

The star of this flamboyant group of lichens is C. diversa. It is slightly more yellow in colour than the others and usually has wider cups which often have small projections at their edges, each with a red tip. Most charming of all, like some other species it sometimes has miniature cups within its cups. With a little hunting this can be found in Kew Gardens.

Among all the green or grey green pixie cups which are the ones that are most numerous C. fimbriata is probably the most common. It often has more of a champagne flute shape with greyish green powder in its cups. Besides heaths it is worth looking for on old walls in cemeteries and even in gardens. It is often confused with the much scarcer common cup lichen C. pyxidata which is smaller and can have brown edges to its cups. The latter species may still be found in Brompton cemetery. Among the other green pixie cup lichens C. humilis is noticeably a brighter green, C. squamosa tends to be a lot more scaly and C. pocillum prefers more chalky soils. It can be found on Box hill.

There is another quite different group of Cladonias often referred to as the reindeer mosses. This is because one species is a major food source for domesticated reindeer and wild caribou which even dig it out of snow in order to eat it. This is C. rangiferina which is largely confined to the Scottish mountains in Britain. However, we have one or two similar species here in London. They all have highly branched, repeatedly forked stems with many tips and tend to form small cushions on the ground in heathland. C. furcata is probably seen the most as it is also found in woodland. It is generally less branched then the others, browner and with brown tips. C. portentosa is highly branched forming dense, yellowish-green cushions with tips pointing in all directions and C. rangiformis looks more coral-like and usually has some scales on its lower branches. All three of these “reindeer mosses” can be found on Esher Common along with most of London’s other Cladonias.