Witches’ Herbs & Ancient Ferns: London’s August Mysteries"
As summer wanes, mugwort’s silver leaves whisper of medieval magic—used to repel moths, cure carbuncles, and ward off airborne poisons. On August 6th, uncover why Artemisia’s hallucinogenic cousin flavors absinthe, where to find golden-scaled ferns on Hampstead Heath, and how to distinguish shield ferns by touch alone. Discover the "coal" hidden beneath mugwort roots and the alien ferns creeping into London’s cracks.
Return on August 6th—when the veil between botany and sorcery thins.
Article
Mugworts and Wormwoods
Another plant that comes very much into focus this month is Mugwort Artemesia vulgaris. It is a tall plant which is common beside roads and in waste places both here and across the rest of Europe. Its Latin name Artemesia comes from the goddess Artemis who first received this healing herb from the centaur Chiron. Its English name, less romantically, is thought to be connected to its old use as a moth repellent. Since Anglo Saxon times it has had many connections with sorcery.
Its leaves were thought to turn north under the action of magnetism. Fully grown specimens were thought to produce a ‘coal’ beneath them which, if dug up on Midsummer’s Eve, was an excellent cure for carbuncles. It was also considered useful against ‘venoms which fly in the air’. Considering this history it is not surprising that carvings of its deeply cut leaves can be found in many churches, especially on medieval roof bosses.
If a larger, darker, less felty mugwort is encountered it is likely to be Chinese mugwort A. verlotiorum. This plant has also been with us for a long time. It arrived from China in the seventeenth century and being the more scented of the two was used in medieval scent bags. A hybrid of the two has been found on Tottenham marshes. Other closely related scented plants are the wormwoods. The Latin name of wormwood A. absinthium suggests correctly this highly scented species is an ingredient of absinthe. It is also an ingredient of the liqueur Chartreuse. An oil made from the plant was known to cause hallucinations and also cause objects to change colour. Considering this it seems a poor choice to include in an ointment which was sold to protect people from being visited by goblins at night. The rest of the mugworts and wormwoods in London, which include tarragon, are mainly non-persistent aliens which just turn up from time to time especially along the Thames.
Ferns and Fungi
August is the perfect month to get to know and enjoy not only our wild native ferns in London but also a number of the alien ferns we grow in our gardens. This is because virtually all ferns are now fully unfurled and many are shedding spores usually from the undersides of their leaves. To help make a field identification it is well worth getting to know the names of the various different parts of a fern. The spore producing structures sporangia are usually in groups (sori) and covered in a membranous flap (indusium) whose shape is often helpful in identifying a particular fern. Also how divided the fern frond is important. If just divided once into a simple row of leaflets it is called pinnate e.g. polypody. If divided twice it is bi-pinnate e.g. male fern and if divided three times tri-pinnate e.g. Broad buckler fern.
It is quite remarkable the range of different leaf shapes in this ancient group of plants. The many different shades of green and the various degrees of dissection of their leaves is what makes them so attractive, especially when clustered together in gardens. Generally it is easy enough to identify London ferns by their leaf shape alone but there are some exceptions.
Our most common woodland fern, the male fern Dryopteris filix-mas is usually identified by its sparsely scaly stem rachis and kidney-shaped indusia on the undersides of its leaves. However, in London there are also two other male ferns both with scalier stems. If the stem is densely covered in golden-coloured scales and the leaves are shiny it could well be the Yellow Golden-scaled Male fern Dryopteris affinis subsp. affinis and if the leaves are not quite so shiny and there are fewer scales possibly the Common Golden-scaled Male fern D. a. borreri. Fortunately all three occur on Hampstead heath where comparisons can be made. There can also be confusion between the Broad buckler fern Dryopteris dilatata and the Narrow Buckler fern D. carthusiana.
The Broad buckler fern is also common in London woods and usually easily recognised by its large triangular-shaped tri-partite leaves. There is also a distinct stripe down the centre of the scales on its stem. The Narrow Buckler fern in comparison has much narrower fronds and no stripe on its scales. Again both can be found on Hampstead heath, including their hybrid.
Shield ferns Polystitcum spp. are another group that can sometimes cause confusion. They have such attractive highly dissected leaves they are very popular with gardeners. The two most likely to be encountered are the Soft Shield fern Polysticham setiferum and the Hard Shield fern P. aculeatum. Just stroking them both you can usually tell the difference.
The first is soft to the touch and the second much stiffer. If still confused the Soft Shield fern is light green, glossy and its lower leaves (pinnae) are the same length as those more centrally placed on its frond. The Hard Shield fern, which is more often seen in gardens, is a darker green and its lower leaves are just half as long as those more centrally placed. Although there are three different spleenworts (Asplenium spp.) in London their leaf shapes are so different they are all easily identified. All of them are found as small ferns on walls.
The Black spleenwort Asplenium adiantum-nigrum looks a little like a miniature male fern (5-20 cms.) except with triangular-shaped leaves. Wall rue A. ruta-muraria has leathery leaves similar in shape to those of garden rue (Ruta graveolens) and Maidenhair spleenwort A. trichomanes has long black hair-like stems which carry two rows of small round leaves. All three can be found on masonry in Lesnes Abbey woods.
Another closely-related spleenwort is the Rusty-back fern Ceterach officinarum which is also found on walls. The wavy edge of its leaves and the dense covering of rusty-coloured scales underneath them make it instantly recognisable. Alien ferns that we grow in our houses and gardens are starting to be found more often in wild situations especially in central London. The cause of this is still uncertain but you might expect to encounter possibly five different Brake ferns (Pteris spp.), three different Holly ferns (Cyrtomium spp.) and occasionally a slightly different Shield or Maidenhair fern. Other places noted for their wide range of ferns include Harrow Weald Common, Oxley wood and Stanmore Common.
The latter site also boasts four different horsetails i.e. Field horsetail Equisetum arvense on dry ground, Water horsetail E. fluviatile which is usually found beside water, the Great horsetail E. telemateia which seems to like railway embankments and there is just a faint possibility of the Marsh horsetail E. palustre which unsurprisingly likes marshy ground.
The autumn fungi often makes a hesitant start in the latter part of August. In the woods you may see precociously early earthballs, puffballs, stinkhorns, grisettes as well as various brackets and the Brown roll rim. On the roadsides a number of Agarics such as Agaricus bitorquis can suddenly appear and in meadows various dung-loving species such as the Psathyrellas may be seen in numbers. In gardens it is the rusts and mildews that tend to get noticed, especially on hollyhocks and roses.
