Tree Lupin, Lupinus arboreus

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A Tree Lupin in the garden

Tree Lupin, Lupinus arboreus

Tree Lupin, Lupinus arboreus.

Our Tree Lupin, Lupinus arboreus, is in flower in the back garden. Its pale yellow flowers are a contrast to other flowers at the moment, such as the pink and white of Sweet Rocket (Hesperis matronalis) and the red-flowered climbing Rose ‘Allen Chandler’. There is a blue shed behind the Tree Lupin, giving more contrast, and a Golden Hop (Humulus lupulus ‘Aureus’) trailing up a support next to it, whose leaves match the colours of the lupin. The lupin’s leaves are silky, grey-green and palmately-lobed, contrasting in form, as well as staying green throughout the winter.

Tree Lupin, Lupinus arboreus

Tree Lupin, Lupinus arboreus, with Golden Hop (Humulus lupulus ‘Aureus’)

Our Tree Lupin really belongs in the garden and it’s easy to forget that I only planted it three years ago. I bought it as a potted plant from Hethersett Plant Fair (note 1) at the beginning of May 2022 and planted it a couple of days later.

The Tree Lupin isn’t a tree, and never will be. It’s a short-lived shrub, lasting up to seven years. Our plant is now 1.5 metres (five feet) tall and about 1.2 metres (four feet across). The RHS website says that plants can grow to 1.5 – 2.5 metres tall with a similar spread. Wikipedia gives a maximum height of 2 metres (7 feet) tall in sheltered positions, but more typically 1 – 1.5 metres (3 – 5 feet) tall. I prune our plant whenever it grows across a path and it doesn’t seem to mind.

Our garden soil is very well-drained sandy loam and this is just what Tree Lupins prefer (note 2).

Tree Lupins in the wild

The Tree Lupin is a native of North America, particularly parts of California. It has been introduced into other parts of the world, including other parts of North America (British Columbia, Oregon and Washington), South America (Argentina, Chile and Falkland Islands), Australia (Tasmania and Victoria) and New Zealand (North and South Islands). In Europe it now grows in Great Britain and Ireland.

Lupinus arboreus is a neophyte and was introduced into the British Isles in 1793, when it was treated as a tender plant requiring greenhouse protection. It was first recorded in the wild in 1926 at Freshfield in South Lancashire. It is now well established, with a largely coastal distribution. But there are inland records too: Tree Lupins grow happily on well-drained soils and are given hardiness rating “H4” by the Royal Horticultural Society (“hardy through most of the UK (-10C to -5C)”).

Tree Lupins grow well in sand dunes (where they are widely planted) and on Cornish china-clay tips, as well as on roadsides, railway banks and on waste ground.

Distribution of Tree Lupin, Lupinus arboreus. Image from BSBI Plant Atlas.

Distribution of Tree Lupin, Lupinus arboreus. Image from 2020 BSBI Plant Atlas.

Tree Lupin flowers smell faintly of honey.

The Wild Flower Finder website has photographs of Tree Lupin flowers at different stages of development. Like our plant, the flowers are yellow but the First Nature website has a photograph of a flower with a tinge of mauve. Mike Crew’s Flora of East Anglia website has pictures of white and blue flowers as well as the more usual yellow. Flowering is usually from June until August but it is a bit earlier this year after the sunny and very dry spring.

Although each Tree Lupin plant is short-lived, the plants persist by seeding around. They produce large amounts of long-lived seeds in stiff, hairy pods.

Tree Lupin are members of the Pea family, the Fabaceae (formerly Leguminosae). They have a similar  shrubby, short-lived growth habit to our native Common Gorse (Ulex europaeus) and Common Broom (Cytisus scoparius).

Members of the Fabaceae have nitrogen-fixing bacteria in root nodules (in Tree Lupin, from the genus Bradyrhizobium) . These capture nitrogen from the atmosphere and convert it into ammonia (NH3) or ammonium ions (NH4+), which the plant can use to grow. This is especially useful in poor soils.

Other Lupins

There are over 199 species of Lupinus worldwide. Most are from North and South America, with some from North Africa and the Mediterranean region.

Mike Crew’s Flora of East Anglia website gives details of two other species of lupin found in our region of Britain:

Narrow-leaved Lupin, Lupinus angustifolius

The Narrow-leaved Lupin, Lupinus angustifolius, is an annual species with very narrow leaflets and blue flowers. It comes from southern Europe and has sometimes been used as a fodder crop. Like other lupins the seeds contain bitter-tasting toxic alkaloids but there is some natural variation and plant breeders have produced low-alkaloid, edible forms (note 3).

Russell Lupins, Lupinus x regalis

Most of us are familiar with Russell Lupins, Lupinus x regalis, which are the common garden Lupin, available in many colours. They are hybrids between the Tree Lupin and the Large-leaved Lupin, Lupinus polyphyllus. They are herbaceous perennials and have inherited this growth habit from the Large-flowered Lupin and a branching habit from the Tree Lupin.

Russell Lupins are often referred to as “”Russell Hybrids”. They grow to 1.5m (five feet) in height and have flowers in many shades of yellow, pink, red, blue, purple or white. Bicoloured flowers are common. Although both parents are from North America, Russell Hybrids were developed on two allotments in York by the horticulturalist George Russell in the first half of the 20th century (note 4).

Pink Russell Lupins, Lupinus x regalis

Pink Russell Lupins, Lupinus x regalis, at Kentwell Hall, Long Melford, 21st May 2025.

We don’t grow Russell Lupins in our current garden, though they would probably do well. Our previous garden in Norwich was full of Garden Snails (Cornu aspersum). These took a particular delight in eating Lupin leaves, tearing them apart with relish and small plants disappeared overnight. Snails weren’t a problem when I lived near Aberdeen and we had many fine Russell Lupins in the garden.

Russell Lupins in a Scottish garden.

Russell Lupins in a garden near Nethybridge in Scotland, June 2024.

Tree Lupins and wildlife

Lupin flowers are popular with bumblebees and in the last few days worker Buff-tailed Bumblebees (Bombus terrestris) have been visiting the flowers, starting at the bottom of a flower spike and working their way up towards the top.

Bombus terrestris worker on Tree Lupin

Bombus terrestris worker visiting Tree Lupin flowers.

On a sunny day the mirid bug Closterotomus trivialis uses our Tree Lupin leaves as a place to sunbathe and, presumably feed. (The bug, a recent arrival from the Mediterranean, is polyphagous, that is, it feeds on a wide range of plants.)

Closterotomus trivialis

Mirid bug Closterotomus trivialis on a Tree Lupin leaf.

Perhaps less welcome is the Lupin Aphid, Macrosiphum albifrons, which can be found on various species of lupins, including Tree Lupin and Russell Lupins.

Lupin Aphids.

Lupin Aphids. Photograph by Vanna Bartlett.

We haven’t found any (yet) this year but in previous years we have had high numbers on our Tree Lupin. We let nature take its course, glad of another species of insect in the garden, but the aphids can sometimes cause serious damage and plants that have been badly debilitated by the aphids can die. The excellent Influential Points website has more details and photographs.

Happy memories!

I have several happy memories of lupins.

Firstly, growing Russell Lupins with my Mum’s help when I was four or five years old. We forgot to water the seedlings but they survived and were the first plants I grew in what started off as a sandpit for me to play in and ended up as my very first garden.

Russell Lupins also remind me of our garden near Aberdeen when we moved to Scotland. I find the smell of Russell Lupin flowers a little peppery and we once made the mistake of picking some of the flowers for a vase. They were soon banished outside; never again.

My first definite memories of Tree Lupins is from the Suffolk coast near the Minsmere RSPB reserve, seen when walking and birdwatching in the area.

More recently, I think of Tree Lupins on the banks of the railway cutting at Felmingham in North Norfolk, where Small-flowered Catchfly grows. The soil is very sandy, which provides good winter drainage, and disturbed, which allows both the catchfly (an annual) and the Tree Lupin to spread by seed.

Finally, earlier this month I went to see the fabulous Oysterband perform at Folk On The Pier in Cromer, on the North Norfolk coast. We walked along the cliff tops from Overstrand to Cromer and, as we started to descend into Cromer there were some Tree Lupins in flower here too. It was a great day out: sunshine, the coconut smell of Common Gorse, good company, tea and cake, fish and chips, a superb concert …and lupins. Perfection!

Tree Lupin in our garden

Tree Lupin in our garden, earlier today.

Notes

Note 1 – Hethersett Plant Fairs are organised by Norfolk Plant Heritage and there are two a year. The fairs are held at Hethersett Village Hall (a few miles west of Norwich) in early May and late August.

Note 2 – The Gardeners World website recommends growing Tree Lupins in full sun, in rich soil (“Acidic / Chalky / Alkaline / Clay / Heavy / Moist / Well Drained / Light / Sandy”). In our north-facing garden our Tree Lupin is in sun for much of the day in summer, but doesn’t receive much direct sunshine in winter.

Note 3 – Several years ago I grew two varieties of Narrow-leaved Lupin, on the allotment, while taking part in a Garden Organic members’ experiment to test the palatability of lupins bred for human consumption.

It was a very dry summer but in spite of this the plants cropped well. But the seeds were very hard and dry and I had to boil freshly collected seeds for an hour or more to soften them. I then discovered that the taste was still too bitter for my liking. I didn’t try them a second time.

I let a few of the plants self-seed and they were very attractive but they eventually died out.

Note 4 – You can read more about George Russell and his lupins online: “The man who made lupins his life” (Yorkshire Post 2004) and “The Lupin Man of York – George Russell” (God’s Own County blog).

At their peak there were 152 named varieties but in the years after Russell’s death many were lost to Cucumber mosaic virus (CMV) or allowed to self-sow, reverting to their original colours.

American Skunk-cabbage, Lysichiton americanus

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At the beginning of April I met an old friend, American Skunk-cabbage, Lysichiton americanus, in a wet woodland at Buckenham in Norfolk. I was on a BMS (British Mycological Society) foray. Fungi were few but seeing American Skunk-cabbage was a highlight of the day.

I hadn’t seen the plant for several years but I had strong memories of its magnificence and it didn’t disappoint. It is stunning!

American Skunk-cabbage,Lysichiton americanus

American Skunk-cabbage, Lysichiton americanus, Buckenham, Norfolk, 5th April 2025.

There is something almost alien about American Skunk-cabbage’s big, bright yellow flowers, which emerge in April, slightly ahead of the leaves. It is bigger and bolder than our own Cuckoo Pint, Arum maculatum, which I wrote about in March 2018, though clearly related.

Both plants are members of the family Araceae and have flowers borne on an inflorescence known as a spadix, partially enclosed in a sheath (a leaf-like bract known as a spathe).

The spadix emits a scent to attract pollinators and in Lysichiton americanus this is a musky smell to attract adult rove beetles. The smell resembles the spray of skunks (note 1), hence “Skunk-cabbage”. I’ve never seen or sniffed a skunk so the smell reminded me of plastic with an added top note of Fox and I found it intriguing rather than unpleasant. (The Oxford Plants 400 website is less complimentary, describing the scent as “unpleasant, faeces-like, indole-rich“.)

Insects are often attracted to yellow objects and the bright yellow spathes of the plants at Buckenham were attracting sunbathing flies, including Eristalis hoverflies. I also noticed a few Owl Midges inside one flower (note 1).

American Skunk-cabbage, Lysichiton americanus

American Skunk-cabbage, Lysichiton americanus, attracting flies.

The genus name Lysichiton is derived from two Greek words: lysis, meaning dissolve, and chiton, meaning a cloak or armour. These describe the way that spathe enclosing the inflorescence withers soon after flowering (note 2).

Lysichiton flowers are hermaphrodite but individual plants have male and female phases. The spathe is protogynous – the flowers start off functionally female and then become male.

Lysichiton americanus is, as the specific name suggests, native to America, particularly western North America  from Alaska south to California, where it is known as Western Skunk-cabbage (note 3).

Native American tribes would sometimes eat parts of the plant but not raw. Like our native Cuckoo Pint, American Skunk-cabbage contains calcium oxalate crystals (raphides). Thorough cooking or drying can make it edible but I’m not tempted. Statements like “the native North American Indian tribes would cook [the leaves] in several changes of water, the end result being a tasteless mush” don’t make me want to experiment.

Encounters with Skunk-cabbage

American Skunk-cabbage has been introduced to several European countries: Belgium, Denmark, Finland, Germany, Great Britain, Ireland, Netherlands, Norway, Sweden and Switzerland. It is a plant of stream sides, boggy places and swampy woodland in both its native and introduced range.

American Skunk-cabbage, Lysichiton americanus

American Skunk-cabbage, Lysichiton americanus, in the bog garden at Forde Abbey (27th April 2008). Some of the spathes have withered.

My first encounter with American Skunk-cabbage was in the wonderful Cruickshank Botanic Garden in Aberdeen, when I was studying Botany in the early 1980s. I often visited the garden at lunchtimes and sometimes shared a sausage roll with the gardener’s dog, a golden retriever with an expression that even a penniless, hungry student couldn’t refuse. In spring, the stunning yellow flowers of Lysichiton americanus were one of the many highlights of the garden (note 4).

I have vivid and happy memories of my time in Aberdeen but sadly no pictures of Lysichiton americanus. But when I saw the plant in 2008, when we visited Forde Abbey, near Chard in Somerset, I did take some photographs. It was late April and Lysichiton americanus was flowering in the bog garden. The clumps of glossy, leathery foliage give the plant a passing resemblance to a cabbage.

Even when Lysichiton americanus has finished flowering, its leaves are very distinctive and noticeable. When we stayed in Oban in May 2018 we recognised American Skunk-cabbage plants on the banks of a stream on the road north of the town to Ganavan Sands. Plants had clearly spread along the stream – probably from an ornamental pond higher up the hillside – and were heading down through a bog towards the coast (note 5).

American Skunk-cabbage

American Skunk-cabbage spreading, near Oban. 19th May 2018.

Invasion!

The Oban plants illustrate some of the story of Lysichiton americanus in the British Isles.

American Skunk-cabbage was introduced to cultivation here in 1901 and, like many introductions, decided it liked being here. It escaped into the wild in 1947, in Surrey. Since 2000 it has been recorded in roughly 1,000 new sites (an eight-fold rate of increase compared with the previous 40 years). It is now considered invasive and has been banned from sale since 2016. It is now illegal to plant (or otherwise cause to grow) Lysichiton americanus in the wild and gardeners must prevent any Skunk-cabbage growing in their garden from escaping into the wild.

Lysichiton americanus can spread by its rhizomes and by seed. A large seed bank can build up in the soil and can remain viable for around 8-9 years. Unchecked, the plant can eventually dominate large areas, especially in swampy woodland.

American Skunk-cabbage now has its own page on the Scottish Invasive Species Initiative website, where you can report sightings. There is also a PDF file on the GB Non-native Species Secretariat website.

Herbicides are often used to control American Skunk-cabbage but they should only be used by qualified people when the plant is growing near water (as it usually is) because of the harm they can cause to aquatic life. A safer but more labour intensive method is to dig out the rhizomes by hand. You will probably have to wear wellies (or even a full waterproof suit) to do this. Tiny pieces of rhizome can grow into plants but the good news is that the plants only flower when three or more years old. Cutting off flowers will prevent established plants from setting seed.

Mixed Feelings

I have mixed feelings about invasive, non-native plants. They do need to be controlled but it is no accident that they are growing here – they are magnificent. I can understand why they were introduced into gardens in the first place, particularly before we understood they could have a detrimental effect on our native flora.

For me, American Skunk-cabbage occupies a similar place in my heart to other spectacular invasive plants such as the toweringly magnificent Giant Hogweed (Heracleum mantegazzianum). Yes, these plants are invasive, but I love them. (I am less keen on Japanese Knotweed, Reynoutria japonica.)

Fortunately Lysichiton americanus can still be seen in some gardens, including Cambridge University Botanic Garden, where it grows on its own small island in the middle of a pond. Maybe that’s the best compromise, though it doesn’t quite give the thrill of seeing those “wild” plants at Buckenham (note 6).

American Skunk-cabbage, Lysichiton americanus

American Skunk-cabbage, Lysichiton americanus. Buckenham, Norfolk, 5th April 2025

Notes

Note 1 – Skunks are American mammals in the family Mephitidae (related to our Stoat, Weasel, Badger and Otter from the family Mustelidae). They are known for their ability to spray a liquid with a strong, unpleasant scent from their anal glands. Chemically, this is a mixture of sulphur compounds such as thiols , which can smell of garlic, cabbage or rotten eggs. (Thiols are added to natural gas, which is naturally odourless, to allow us to detect its presence.)

In contrast to American Skunk-cabbage, I think the smell of Cuckoo Pint is quite subtle – perhaps “slightly of decay”. It has also been described as “a mixture of mouse, lemon and rotting plant material” to “foul and urinous“. Cuckoo pint flowers attract pollinating Owl Midges rather than rove beetles.

Cuckoo Pint relies on a combination of heat and smell to attract Owl Midges but the spadix of Lysichiton does not heat up to attract insects.

Note 2 – There are two species of Lysichiton worldwide, the other being Lysichiton camtschatcensis, Asian Skunk-cabbage. It has a white spathe and is sometimes known as White Skunk-cabbage, Far Eastern Swamp Lantern or Japanese Swamp Lantern. It grows in northern Japan and on the Kamchatka Peninsula, the Kuril Islands and Sakhalin. Apparently, the flowers are scentless.

Note 3 – There is also an Eastern Skunk-cabbage, Symplocarpus foetidus, another member of the Araceae. Its spathes are mottled with varying amounts of yellowish-green and purple. The spadix emits a strong odour of “fresh cabbage with a slight suggestion of mustard” which attracts blowflies. Spiders often spin their webs at the the entrance to the flowers, to catch the flies.

Note 4 – Later in the year the bright yellow of the Skunk-cabbage was replaced by many other flowers, including the blues of  Himalayan Poppies (Meconopsis) and Gentians (such as Gentiana sino-ornata). Material from the Botanic Garden was extremely useful in Botany practicals. The garden’s Curator, Noel Pritchard, was one of my Botany lecturers and a great plantsman. His knowledge and love of plants inspires me to this day. (He died in 2004 but I’m glad to see there is an annual Noel Pritchard Memorial Lecture in his memory.)

Note 5 – I thought I remembered seeing the yellow flowers of Lysichiton americanus at Oban but of course I was a month too late. Memory plays tricks and my photograph sets the record straight.

Note 6 – The plants at Buckenham are being monitored and I’m told that the population is currently stable.

Cedar Cup, Geopora sumneriana

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Cedar Cup, Geopora sumneriana

Cedar Cups, Geopora sumneriana, in grass beneath a Blue Atlas Cedar tree. Norwich, 9th March 2025.

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.

A young Cedar Cup, Geopora sumneriana.

A young fruitbody of Cedar Cup, Geopora sumneriana, pushing up to the soil surface.

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).

Cedar Cup, Geopora sumneriana

Seen from above: Cedar Cup, Geopora sumneriana. Norwich, 9th March 2025.

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.

Distribution map for Geopora sumneriana (16th March 2025).

Distribution map for Geopora sumneriana from The British Mycological Society Fungal Records Database of Britain and Ireland. [Accessed on 16th March 2025]

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.)

Blue Atlas Cedar

A Blue Atlas Cedar, Cedrus atlantica ‘’Glauca’.

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:

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.

Signs of digging under a Cedar.

Signs of digging under a Cedar (with Winter Purslane).

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).

Cedar Cup, Geopora sumneriana

A single Cedar Cup, Geopora sumneriana, with Common Field Speedwell and Daisy for scale.

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.