Bog Beacon, Mitrula paludosa
Bog Beacons, Mitrula paludosa, 3rd May 2022.
I love looking through the pages of plant or fungi books, dreaming of what I’ll see next.
Page 304 of Sterry and Hughes’ book ‘Collins Complete British Mushrooms and Toadstools’ features ‘Earthtongues, jellybabies and allies’, including the Bog Beacon, Mitrula paludosa. I’ve seen several of the earthtongues and also Jelly Baby fungus, but – until last week – not Bog Beacon.
Last November I visited a lovely bit of wet woodland near Norwich. Wellies were required, as it was very boggy, with lots of Sphagnum moss and a stream running along its edge. Inside the woodland were lots of small pools and I was told that the Bog Beacon, Mitrula paludosa, had been discovered there the previous spring by people doing a plant survey. I made a mental note to come back in the spring.
Reports of Bog Beacon started to appear on the British Mycological Society (BMS) Facebook page in late March (from the New Forest) so Vanna and I cycled out to take a look in early April. We didn’t find any Bog Beacons – we were too early.
A week ago (3rd May) we had another search in the same place. We still needed our wellies, in spite of the dry spring. Our rich reward was a host of golden Bog Beacons, maybe a couple of hundred of them, almost glowing beneath the trees. The English names are very apt – Bog Beacon in Britain and Swamp Beacon in the United States. Each fruit body is bright yellow and borne on an off-white or pale pinky-brown stem. They’re delightful little fungi (note 1).
Bog Beacons, Mitrula paludosa, with Common Alder cones for scale. Photo credit: Vanna Bartlett.
Bog Beacons are saprotrophic, recycling dead plant litter. Our Bog Beacons were clearly growing on last year’s fallen leaves on the surface of the pools. Sterry & Hughes describe the habitat as: “Gregarious on plant remains, often underwater in streams, ditches and pond margins; sometimes with Sphagnum moss.” This fits exactly with what we saw.
Bog Beacons, Mitrula paludosa (with Sphagnum moss).
Sterry and Hughes gives Bog Beacon’s status as “uncommon”.
At the time of writing, there are 842 records of Bog Beacon (Mitrula paludosa) on the NBN Atlas website.
Recent reports of Mitrula paludosa on the British Mycological Society (BMS) Facebook page mostly come from the New Forest, Kent, West Sussex and, further north, Saddleworth (Greater Manchester). The fungi start to appear in March and peak in May or June. They have disappeared by mid September (in Scotland, probably earlier elsewhere).
There are only a tiny handful of records for Mitrula paludosa from Norfolk and none that I know of from the rest of East Anglia. Maybe Bog Beacons are hiding out of sight in other wet but difficult to access woodlands? To enter their boggy habitat requires a pair of wellies and permission to access the land where they’re growing (the latter often a problem in England and Wales).
The Scottish Fungi website mentions their association with seeping water and recommends searching ditches, slow moving streams, sphagnum patches and loch sides. But be prepared for disappontment. The First Nature website warns: “you will not find Bog Beacon where the habitat is unsuitable, but neither should you assume that where the habitat is suitably boggy with plenty of rotting vegetation this ascomycete will appear: more often than not it doesn’t“.
Bog Beacon habitat. Wet woods with small pools full of rotting vegetation and Sphagnum moss.
Mitrula paludosa is an Ascomycete fungus, in the order Helotiales and the family Sclerotiniaceae. (I’ve previously written about some of its relatives, most recently Spring Hazelcup.) Its head, the yellow “beacon”, produces its spores, which are shot out and spread around in air currents.
Bog Beacons are not edible and their odour and taste are “not distinctive“. But they are a feast for the eye and are certainly very photogenic.
The Scottish Fungi website has some very good pictures and the Misidentifying Fungi website also includes some good general habitat pictures (from Park Corner Heath, near Lewes in Sussex). One of my favourites is a lovely photo posted by Lancashire Lad in 2015 of Bog Beacons with Water Crowfoot on the UK Fungi website. The First Nature website is worth a look too, and includes microscopic features (asci and spores).
Outside the British Isles, Mitrula paludosa occurs elsewhere in much of Europe and in parts of Asia, and in the United States and Canada (note 2).
The fungus was first described in 1821 by the Swedish mycologist Elias Magnus Fries. Bog Beacons have been given a variety of scientific names since then and the First Nature website lists them (note 3). In the currently accepted name, Mitrula describes the Bog Beacon’s mitre-shaped cap and paludosa means “of swamp, marsh or bog”.
Notes
Note 1 – Maximum size is 5cm (just under two inches) tall, 4cm of this being stem. Ours were smaller than this.
Note 2 – Mitrula paludosa is featured on page 1361 in Volume 2 of Laessoe and Petersen’s two volume ‘Fungi of Temperate Europe‘. They describe it as “a distinctive species that is unlikely to cause identification problems”.
However, according to Wikipedia, “many related species of Mitrula look identical without microscopic study”, though details it gives are very scanty. There is certainly a similar species on the west coast of the United States, Mitrula elegans, but it doesn’t occur in the British Isles .