The quest for Cedar Cups

Last spring I spent quite a lot of time looking for Cedar Cups, Geopora sumneriana. Cedar Cups are usually found beneath Cedar trees (Cedrus sp.) so the search involved visiting churchyards and parks where these grew. I saw some lovely trees, cycled many miles, visited interesting churches and peered over walls into gardens. I looked longingly at majestic Cedars of Lebanon in parkland, tantalisingly out of reach. (Cedar trees are often on private land.) But I found no Cedar Cups.

My search included some known sites but again I found nothing. One, a Deodar Cedar beside Colney Lane in Norwich, had Cedar Cups underneath it in 2015 but the tree died several years ago and is now just a stump. A Blue Atlas Cedar, in the grounds of County Hall, still looked suitable but yielded no fungi.

Cedar Cups at last!

Last Sunday Vanna and I went for a walk through the grounds of our local university and Vanna noticed a fairly small Blue Atlas Cedar. I went across to it and, not expecting any reward, looked in the short grass beneath the tree. Finally, there they were: Cedar Cups, Geopora sumneriana. I found two fruitbodies and Vanna soon found ten more, on slightly sloping ground to the south and west of the tree. The find was completely unexpected and all the more enjoyable for being deferred.

Like other cup fungi, Geopora sumneriana is an ascomycete fungus. Its sexual spores are produced inside elongated sacs known as asci and, when ripe, are forcibly ejected (note 1) .

Cedar Cups develop over several months as underground spheres before breaking through the surface of the soil. As the cup pushes upwards through the soil it forms a small mound of soil and the entrance to the cup looks like the entrance to an insect nest burrow – an extremely large solitary bee or a Minotaur Beetle, perhaps.

As it continues to grow the Cedar Cup fruitbody reveals itself. Its inner surface is smooth and pale cream when freshly opened, darkening to a light greyish beige. This is the fertile surface of the fungus fruitbody. The outside of the cup is infertile and covered in curly brown fine hairs, which you can see more clearly if you carefully brush off some of the soil. With its creamy interior and hairy exterior I think a Cedar Cup resembles a tiny, split open coconut.

The cup continues to expand and it can reach five to seven centimetres (two to about two and a half inches) in diameter and up to five centimetres (two inches) tall. Mature fruitbodies usually split into five to seven irregular, star-like rays. The First Nature website has photographs of a couple of mature Cedar Cups and pictures of spores and asci.

We found twelve cups but Cedar Cups can sometimes be found in much larger numbers. The Worcestershire Record website records a remarkable mass fruiting of over 100 fruitbodies scattered on the northern side of a single thirty year old tree. The Wildlife Trusts website has a video presented by the FUNgi Guy, who gave up counting at 170 Cedar Cups (note 2).

In Norfolk, Cedar Cup is quite a rare find. It fruits in spring, usually in March or April. Up to the end of 2023 there were 16 records (from 14 sites) in Norfolk, seen between 25th February and 29th April. Just one record was added for 2024, so maybe I didn’t find any Cedar Cups last spring because it was a poor fruiting year. Like many fungi, there seem to be good and bad years. Cedar Cup was seen in exceptionally large numbers during the winter of 2016-17.

The Fungus Records Database of the British Isles (FRDBI) had 221 records when I looked today. Records for Geopora sumneriana mostly come from southern England, though there is a record for Northern Ireland (note 3). Cedar trees grow quite happily further north and we had a Blue Atlas Cedar in our garden near Aberdeen when I was a child, but presumably the conditions don’t suit the fungus.

The Global Biodiversity Information Facility (GBIF) website shows the wider distribution of Geopora sumneriana across Europe (as far north as Denmark) and into Asia. Geopora sumneriana was recorded for the first time from Pakistan in 2018.

Associations

Cedar Cup is, as the name suggests, normally associated with species of Cedar (Cedrus sp.) and the fungus presumably forms a mycorrhizal relationship with the tree. However, Yew (Taxus baccata) is an occasional associate (note 4) and Cedar Cups have also been recorded from beneath a Holm Oak (Quercus ilex) in Kew Gardens.

Geopora sumneriana likes to grow in dry places and Cedars, Yew and Holm Oak all provide these conditions. Well drained soil seems important too and trees with bare soil or short grass underneath them are probably best. (These conditions certainly make it easier to look than under trees surrounded by a bed of nettles.)

Cedars are widely planted non-native trees in the British Isles, particularly in private parkland but also in churchyards and public areas such as parks. There are three species worldwide and all can be found in Britain: Cedar of Lebanon (Cedrus libani), Deodar Cedar (Cedrus deodara) and Atlas Cedar (Cedrus atlantica).

A mature Cedar of Lebanon, Cedrus libani, is instantly recognisable with its characteristic flat layers of branches. Atlas Cedars have clusters of short needles and their branches usually point upwards; a glaucous form (Cedrus atlantica ‘’Glauca’ ) is widely planted. Deodar Cedars has longer, soft needles that droop at the end of the branches. Looking at the branch tips, the mnemonic “ascending = Atlas, level = Lebanon, and drooping = Deodar” is quite useful.

The Cedar of Lebanon has three distinct forms with different geographical ranges and these sometimes treated as separate species:

• Lebanon Cedar (C. libani var. libani) from the mountains of Lebanon, western Syria, and southern-central Turkey.
• Turkish Cedar (C. libani var. stenocoma) from the mountains of southwestern Turkey.
• Cyprus Cedar, (C. libani var. brevifolia) from the Troodos Mountains in Cyprus.

The Tree Guide UK website has a useful comparison of Cedars, as does the Royal Forestry Society’s species profile.  I often consult pages 90 – 93 of the “Collins Tree Guide” by Owen Johnson and David More (Harper Collins, 2004).

I did a rough count of FRDBI records to see where Cedar Cup records have been found. Most are simply recorded as being associated with “Cedrus sp.” but where the tree has been identified to species, 21 records are with Atlas Cedars, eight records are with Cedar of Lebanon and just one is associated with Deodar Cedar (note 5).

Signs of Digging

When I told my friend James Emerson about the Cedar Cups we’d found he commented “I suspect that sometimes they get eaten by squirrels, as I have looked for them in several other places with previous records and not found them”.

This got me thinking. I’ve often found signs of digging under Cedar trees.

On Wednesday we found more Cedar Cups, this time under a Deodar Cedar in Norwich. There was one fruitbody in the ground and another had been dug up and was lying on top of the soil. There were lots of other holes, presumably made by Grey Squirrels.

Intrigued, I did an online search.

Geopora sumneriana has some relatives in North America, including Geopora cooperi. G. cooperi is a hypogeous fungus – it spends its time underground and “rarely sees the light of day – leaving squirrels, other rodents, and insects as the primary agents for spore dispersal“.

I also found the study “Diets of Native and Introduced Tree Squirrels in Washington” (note 6), which found that several species of squirrel ate hypogeous fungi throughout all seasons, with spores present in most samples of their faeces. One of the species was the Eastern Grey Squirrel, Sciurus carolinensis, which is an introduced species in Washington and is the Grey Squirrel that has been introduced into Britain.

Geopora sumneriana does pop up above the ground but its fruitbodies spend a lot of time  beneath the soil and perhaps squirrels do like eating them and, in doing so, spread the spores.

The odour of the American Geopora cooperi is described as “not distinctive, or sour and reminiscent of bad apple cider“.

Most descriptions of Geopora sumneriana say it has a smell that is “not distinctive” and I would describe what smell I can detect as soil with something vaguely fungal. However, in parts of Northern India (including Kishtwar National Park) Geopora sumneriana “is frequently consumed by the indigenous people due to its rich aroma, abundance and flavour“. Maybe squirrels also detect a “rich aroma” and good flavour?

In Britain, Geopora sumneriana is thought to be poisonous when raw and possibly even when cooked. Even if it tasted delicious, it wouldn’t be a good idea to harvest such a comparatively rare fungus and “in any case the flesh is insubstantial“.

Other UK Geopora

The 1996 paper by Yao and Spooner, “Notes on British Species of Geopora” (Mycol. Res. Vol. 100, pp72 – 74) is available as a PDF online and lists several other British species. Two of these, Geopora arenicola and Geopora cervina, are rather rare but have been found in West Norfolk. They tend to grow in places with sandy soil but aren’t associated with Cedars. I haven’t seen either of them.

Geopora means means “earth cup”. Synonyms for Geopora sumneriana include Sepultaria sumneri and Sepultaria sumneriana. Sepultaria means “underground tomb”. Both names are appropriate for this hypogeous or partially hypogeous genus of fungi.

In Welsh, Cedar Cup is Cwpan Cedrwydd.

The specific name of Cedar Cup, sumneriana, is named after the American ichthyologist, zoologist and writer Francis Bertody Sumner (1874 – 1945).

Notes

Note 1 – Ascomycetes are known as “spore shooters”. Once the spores are mature the ascus bursts open (usually at the top) and spores are released. Wind currents frequently disperse the spores but sometimes animals can move them on their feet (as in Olive Salver, Catinella olivacea, which I wrote about in December 2022). Some species can forcibly eject their ascospores for distances of up to 30 cm (12 inches).

I’ve written about several other ascomycete fungi on this blog, including the cup fungi Spring Hazelcup, Encoelia furfuracea,  Scarlet and Ruby Elfcups (Sarcoscypha sp.) and Alder Goblet (Ciboria caucus).

The singular of asci is ascus, from the Greek askós, meaning sac or wineskin.

Note 2 – The FUNgi Guy cried “Yabba Dabba Doo” when he found them; I did something similar, though internally.

Note 3 – A login is required to access the FRDBI database. Membership of the British Mycological Society gives this access, which is well worth considering if you have more than a casual interest in fungi.

The distribution map is from the FRDBI (made available under a Creative Commons BY-NC-SA Attribution – Non Commercial – Share Alike licence).

The NBN Atlas website shows the British distribution too.

Note 4 – At the time of writing there is one record for Cedar Cups growing with Yew on FRDBI. Last summer I visited a house near the centre of Norwich where Cedar Cups have been found under a Cedar tree and also with Yews at the far side of the garden, probably beyond the range of the Cedar’s roots.

Note 5 – I know of at least two Norfolk records of Cedar Cups associated with Deodar Cedar. One was recorded as “Cedrus sp. and the other is very recent so hasn’t yet reached FRDBI.

Incidentally, the Cedars I’m writing about are “true cedars”. Trees like Western Red Cedar (Thuja plicata) are conifers too, but are not closely related.

Note 6 – Aaron N. Johnston, Stephen D. West, and W. Matthew Vander Haegen (2019). “Diets of Native and Introduced Tree Squirrels in Washington”. The Journal of Wildlife Management Vol 83(7), pp1598–1606.

Spores from fungi – species of Rhizopogon (false truffles), Geopora, and Melanogaster spp. – were found in most faecal pellets.