Japanese Kerria, Kerria japonica

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Last week’s beautiful and unexpected plant treat was a single-flowered Kerria japonica (Japanese Kerria) in a front garden on Earlham Road in Norwich.

Too many gardens have become barren car parks and it is always a pleasure to see one full of plants and even better when it’s full of unusual and interesting plants. Floating above a carpet of tiny Lesser Celandine flowers, the Kerria japonica was stunning, a cheery yellow on a mostly grey spring day.

Kerria japonica

Kerria japonica (Japanese Kerria). The single-flowered form. 21st March 2024.

Kerria japonica (single flowered)

Like the plant I saw on Earlham Road, the wild form of of Kerria japonica has open, single yellow flowers with five petals (note 1). The flowers remind me of the beautiful yellow rose Rosa xanthina ‘Canary Bird’ which we grow in our back garden. This is not surprising, as roses and Kerria are both members of the Rose family, Rosaceae.

But I’ve only seen single-flowered form twice. I usually see the double-flowered form in gardens, Kerria japonica ‘Pleniflora’.

Kerria japonica ‘Pleniflora’

I think Kerria japonica ‘Pleniflora’ lacks the charm of the single-flowered form but it’s still a cheery plant and it was always easier to find in garden centres. I first grew it as a ten year old child in my garden in Scotland and it brings back happy memories.

Kerria japonica spreads by suckering shoots to form a thicket of stems and one of these shoots spread from a neighbouring allotment through a Lawson’s Cypress hedge into the edge of my plot, where it was a welcome visitor.

Kerria japonica 'Pleniflora'

Kerria japonica ‘Pleniflora’ in our back garden. Early April 2017.

I dug up some of the suckers and introduced them into our garden at home. We were planting up Grapes Hill Community Garden in Norwich at the time (spring 2011) and I used another sucker to introduce Kerria japonica ‘Pleniflora’ there too.

An Adaptable Plant

In the wild, Kerria japonica grows in in thickets on mountain slopes in China, Japan and Korea. It is the only species of Kerria.

Both forms of Kerria japonica are cheerful, adaptable and long flowering shrubs. The main flowering period is spring, from March until early May, but there can be a smaller flush of flowers in August.  Kerria japonica has alternate, simple “birch-like” leaves with a doubly serrated margin.

Kerria japonica grows happily in many different aspects, from full shade to full sun. I think it looks at its best in dappled shade; flowers soon bleach in full sun. It tolerates most soil types but dense soils can sometimes cause the roots to rot. I have grown it in loam and in rather sandy soil.

With its suckering habit Kerria japonica soon develops into a thicket of tall, graceful stems, which can cover up a wall or fence, even in dark corners or against north-facing walls.

Stems grow to six to ten feet (1.8 – three metres) tall and the plant can spread to a similar width. Any spare suckers are easy to chop off with a spade and can be used to make new plants and, perhaps, new gardening friends. But this is the way the plant renews itself, so leave some to grow. Old, dead stems can be cut back to allow air into the centre of the shrub and to keep it tidy. The time to prune is after flowering, in June and July. It’s best to take cuttings from August to October, though I’ve dug up roots in early spring and, with enough watering, they’ve taken well. (But please read below about Kerria Twig and Leaf Blight below before you give away cuttings.)

Kerria and Wildlife

The Gardeners’ World website says Kerria ‘Pleniflora’ has no particular known value to wildlife in the UK. Double-flowered plants tend to lack pollen and nectar, so are usually pretty hopeless for insects. However, on one sunny day in early April 2017 we saw two species of hoverfly and a Conopid fly visiting the flowers in our back garden (note 2). The hoverflies may have been attracted by the yellow flowers rather than any reward; the Conopid fly would have been hanging around waiting for a solitary bee to parasitise.

I haven’t seen the single-flowered forms of Kerria japonica often enough to see any insects on the flowers. The Wildflower Web website says that “the plant is also a favorite of pollinators, including bees and butterflies, making it a great choice for those looking to attract wildlife to their garden”. Please let me know if you have any observations.

Kerria japonica 'Pleniflora'

Seeing double: Kerria japonica ‘Pleniflora’ with Syrphus sp. hoverfly. 2nd April 2017.

Kerria japonica and Myopa sp.

Kerria japonica and Conopid fly (Myopa sp.). 2nd April 2017.

Other Names

Kerria is named after the Scottish plant collector William Kerr (note 3). The specific name “japonica” refers to Japan.

As well as Japanese Kerria, Kerria japonica is known as Jew’s Mallow and Kerria japonica ‘Pleniflora’ is sometimes known as Bachelor’s Buttons. The Wildflower Web website also gives the names Easter Rose, Japanese Marigold Bush, Japanese Rose, Miracle Marigold Bush, Yamabuki and Yellow Rose (note 4).

All is not well with Kerria japonica.

In 2018 we noticed that our Kerria japonica was dying back. At first I thought this was because of the long summer drought but more recently I realised the plant had Kerria Twig and Leaf Blight, caused by the ascomycete fungus Blumeriella kerriae. 

The RHS website gives the symptoms:

The Fungi of Great Britain and Ireland website has descriptions and photographs of leaf lesions and microscopic details, including conidia (the asexual spores; the sexual, teleomorph stage of the fungus is not known in the British Isles).

Stem lesions on Kerria japonica caused by Blumeria kerriae

Stem lesions on Kerria japonica caused by Blumeria kerriae.

Since the first infection I’ve cut off and binned the diseased shoots but the fungus has taken hold and the few shoots that our shrub produces no longer grow as tall or as strong as they did in 2017. I know of other people who have dug out their Kerria plants.

Blumeria kerriae spores are thought to be transferred between plants via rain splash, wind, and transfer on contaminated tools.

Blumeria kerriae overwinters on fallen leaves and lesions on the stems then releases spores to reinfect new growth in spring. Spore production has been observed throughout the year on Kerria plants in the UK.

Blumeria kerriae was known in the United States but the first observations in the British Isles date from 2014. Presumably it came here on diseased plant material.

If you grow Kerria japonica and intend to pass on cuttings from your plant, please make sure it has no signs of disease.

Sadly, the occurence of Blumeria kerriae in the British Isles means that Kerria japonica is no longer the tough, disease-free plant it once was.

Happily, the Earlham Road plant looked healthy. I’ll enjoy it while I can.

Kerria japonica

Kerria japonica (Japanese Kerria). The single-flowered form. 21st March 2024.

Photographs by Vanna Bartlett, except for stem with Blumeria kerriae.

Notes

Note 1 – ‘Simplex’ and ‘Golden Guinea’ are named, single-flowered forms of Kerria japonica.  The latter has been given an Award of Garden Merit (AGM) by the Royal Horticultural Society, as has the double-flowered ‘Pleniflora’. There is a variegated form too, if you like that sort of thing.

Note 2 – The hoverflies were a male Eupeodes luniger and a species of Syrphus.

Note 3 – William Kerr was born in Hawick in the Scottish borders. He sent back to Britain examples of 238 plants new to European gardeners and to science. He died in 1814.

Other plants William Kerr brought back include Euonymus japonicus, Pieris japonica, Nandina domestica and Rosa banksiae.

Note 4 – Yamabuki is the Japanese name for the plant. According to the Yamabuki Japan website, he word was first used in the description of spring scenery in the oldest Japanese poem, “Manyo-shu”.

Golden Bootleg, Phaeolepiota aurea

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Golden Bootleg, Phaeolepiota aurea

Golden Bootleg, Phaeolepiota aurea, in Wymondham Cemetery. 23rd November 2023.

On a bike ride in late November 2023 I stopped off in Wymondham Cemetery and ate lunch, sitting on a bench under pines at the top of the hill overlooking the railway.

I was about to leave when I glanced across at an area of quite recent graves and struck gold: four chunky fruitbodies of Phaeolepiota aurea clustered together in the grass (note 1).

Golden in colour

Phaeolepiota aurea has large, golden fruitbodies, with a cap diameter up to 20 or even 30 centimetres (seven to 12 inches). The fungus’ specific name aurea means ‘golden’ and alternative English names, used in the United States, also refer to the colour: Golden Cap, Gold Cup, Alaskan Gold and Golden False Pholiota. There are also references to gold in other languages. It is a very fleshy fungus with a completely dry surface texture.

What about the Bootleg?

When young, Phaeolepiota aurea is covered by a grainy sheath, which also gives it a pale hue, more golden than orange. The sheath soon tears at the cap rim to form a substantial pendant ring or skirt. It resembles a leg in a boot, hence the fungus’ English name.

The genus name Phaelepiota comes from phae-, meaning “dusky” and lepis, meaning scales, although the cap is covered in tiny granules rather than flaky scales.

Golden Bootleg Lookalikes

“Most likely to be confused with the Spectacular Rustgill Gymnopilus junonius” – Nature Spot website.

Being big and bright golden to orange, Phaeolepiota aurea is sometimes confused with another big, bold and similarly coloured fungus, the Spectacular Rustgill (Gymnopilus junonius).

This dramatic fungus has equally large fruitbodies and a stem ring but the “bootleg” is only found in Phaeolepiota aurea. Spectacular Rustgill fruitbodies are always attached to wood (sometimes buried, so this is not immediately obvious) while the Golden Bootleg grows directly on the soil.

Spectacular Rustgill, Gymnopilus junonius

Spectacular Rustgills, Gymnopilus junonius, growing on a dead pine stump. Holkham, North Norfolk, 4th October 2020.

The First Nature website has some great photos of Golden Bootleg and Spectacular Rustgill at different stages of growth, for a full comparison.

The American name “Golden False Pholiota” refers to the slight similarlity to Scalycap fungi (genus Pholiota) but, like Spectacular Rustgill, these grow on wood. They are a brighter orange or orange-yellow, covered in coarse scales (at least when young) and lack the sheath and “bootleg”.

Mistaken Identity

“A little learning is a dangerous thing” – Alexander Pope (1688-1744).

I thought I’d seen my first Golden Bootlegs at Wymondham but I was wrong.

I like to think that I’m now experienced enough to be able to distinguish Golden Bootleg from Spectacular Rustgill (which I’ve seen several times). But as I looked back at my photographs of the “Spectacular Rustgills” I had seen at Sheringham Park in North Norfolk in October 2019 I realised I had made a big mistake. What i’d assumed were Spectacular Rustgills growing on buried wood were in fact Golden Bootlegs.

Fortunately Tony Moverley from the Norfolk Fungus Study Group saw the fungi on exactly the same day and correctly recorded them as Phaeolepiota aurea.

That day Vanna and I were fortunate to see at least thirty fruitbodies, including younger ones still wrapped in a sheath. It was a wonderful sight, even if we didn’t know exactly what we’d seen.

Golden Bootlegs at Sheringham Park

Some of the Golden Bootlegs at Sheringham Park, 2nd October 2019.

A young Golden Bootleg.

A young Golden Bootleg. Sheringham Park, 2nd October 2019.

A young Phaeolepiota aurea

Phaeolepiota aurea still wrapped in its sheath. Sheringham Park, 2nd October 2019. Photo by Vanna Bartlett.

Phaeolepiota aurea – Spectacular and Odd

“This has to be the drama queen of mushrooms” – Wild Food UK website.

Phaeolepiota aurea is featured in the latest edition of “Field Mycology” (Vol 25 (1), February 2024, British Mycological Society) in Alick Henrici’s “Notes and Records” (note 2).

Over a hundred Golden Bootleg fruitbodies appeared in Kew Gardens in mid November 2023 “during a dry period when few agarics of any size were to be seen”, similar in weather conditions and timing to my finds at Wymondham.

Golden Bootlegs had only been recorded once before at Kew, in 2009. It seems that the fungus can exist as a massive mycelium underground, producing fruitbodies at certain times, sometimes trooping in very large numbers. I saw four at Wymondham and 30 at Sheringham Park but in Volume 1 of Laessoe and Petersen’s two volume “Fungi of Temperate Europe” (page 315) there is a photograph of a spectacular fairy ring of Phaeolepiota aurea, which Alick Henrici estimates may contain over 500 fruitbodies – a mind boggling  quantity of Golden Bootlegs!

Phaeolepiota aurea is saprobic, feeding on rich organic matter in the soil. Sometimes the fungus can be found in patches of Stinging Nettles (Urtica dioica) – nettles like places with high levels of nutrients – but the Kew sightings were under Rhododendrons (in 2009) and “some unremarkable grassland” (2023).

Up to the end of 2022, Norfolk had 24 records from 13 different sites, with Golden Bootlegs seen from September to November. A single site at Lynford Arboretum was in a bed of Stinging Nettles (five records) and four more of the records were in grass. Laessoe and Petersen give the habitat as “rich, often disturbed soils, e.g. in fertilized lawns or stands of nettles”.

Cemeteries can have rich and disturbed soils (for obvious reasons) and the part of the cemetery where the Golden Bootlegs were growing had quite recent graves and had produced a massive crop of Shaggy Inkcaps in October 2020.

Shaggy Inkcaps, Coprinus comatus

Shaggy Inkcaps, Coprinus comatus (17th October 2020), growing in the same area of Wymondham Cemetery as November 2023’s Phaeolepiota aurea.

The Sheringham Park site was in a big clearing on the edge of the woods. The grass was very lush and was presumably growing over enriched soil.

But there are plenty of places with enriched soil and most of them don’t have Golden Bootlegs.

Look But Don’t Eat

“All fungi are edible. Some fungi are only edible once.” – Terry Pratchett.

A single Golden Bootleg would make a substantial meal and the fungus looks and smells appetising. The taste is described as “mild and sweet” and the fungus has an enticing, pleasant smell of almonds. Phaeolepiota aurea is sometimes collected for food in Russia and China.

However, the Golden Bootleg is known to cause gastrointestinal disturbance in some individuals. Its almond smell comes from hydrocyanic acid and it can accumulate cadmium from its surroundings (note 3).

The most compelling reason not to eat Golden Bootleg is its comparative rarity in Britain (note 4) and it is best to leave the fruitbodies in situ for others to appreciate (note 5).

A Taxonomic Oddball

“This oddball mushroom has confounded mycologists down the ages as they struggled to fit it in to existing genera” – First Nature website.

Phaeolepiota aurea is the only member of its genus.

Phaeolepiota is in the family Agaricaceae, along with many familiar species, such as Field Mushroom (Agaricus campestris), Giant Puffball (Calvatia gigantea) and Shaggy Inkcap (Coprinus comatus). Its closest relatives are the powdercaps (Cystoderma).

The Earthy Powdercap (Cystoderma amianthinum) looks a little like a miniature Golden Bootleg. It grows in grass and has a finely granular, pale ochraceous yellow to reddish brown cap. The top of its stem is granular but it is scaly further down the stem. Its cap is no more than five centimetres (two inches) across, so there is no chance of confusion.

I’ve seen it in Wymondham Cemetery on a couple of occasions, but none were fruiting on the day I saw the Golden Bootlegs.

Notes

Note 1 – I also found a few things under the pine trees including Crab Brittlegill (Russula xerampelina) and Grey Knight (Tricholoma terreum).

Note 2 – The sub-heading in the article is “Phaeolepiota aurea – spectacular and odd”. I liked it, so have stolen it for one of my sub-headings.

Note 3 – Peter Marren (in “Mushrooms”, British Wildlife Publishing 2012) notes that other fungi contain small amounts of hydrocyanic acid, including the edible Fairy Ring Champignon (Marasmius oreades). Cooking makes these safe to eat. Apparently Phaeolepiota aurea contains larger quantities, but I haven’t found any comparative figures. At least some of the hydrocyanic acid in Phaeolepiota aurea should be destroyed by cooking.

Many plants also contain cyanide compounds, usually cyanogenic glycosides (where cyanides are bound to sugar molecules). These glycosides are broken down in the gut to produce hydrogen cyanide. This is not usually a problem if they are eaten in small quantities (such as the occasional Apple pip swallowed by accident) or if cooked.

For the effects of cooking foods containing cyanogenic glycosides, the report “Natural Toxins in Food Plants“by Hong Kong’s Centre For Food Safety is worth a read.

No amount of cooking will remove cadmium, although to be fair, crops such as rice and cocoa can also accumulate cadmium and I’m not going to stop eating them. If you want to know more, parts of “Cadmium in soils and groundwater: A review” (Kubier A., Wilkin, R. T. and Pichler, T., Applied Geochemistry, Vol. 108, 2019) are available online. Levels of cadmium in soils depend on natural factors such as geology, but human activities such as mining can cause raised levels and cadmium is also found as an impurity in phosphate fertilisers.

Note 4 – Phaeolepiota aurea no longer appears as a rare and probably threatened species on the British Red Data List of Threatened Fungi but it is not common. In the latest edition of “Field Mycology” (Vol 25 (1), February 2024, British Mycological Society) Alick Henrici describes how many members of the BMS on the Autumn Foray in 2003 had their first sighting of the fungus at Gresham’s School in Holt, North Norfolk.

There are currently 150 records for Great Britain and Northern Ireland on the NBN Atlas. Outside the British Isles, Phaeolepiota aurea is found throughout Eurasia and North America. In North America it is “widely distributed” and “not of concern”.

Note 5 – By “others” I include mites, springtails and molluscs, which use fungal fruitbodies for shelter or food. I collect single specimens of fungi that I need to examine microscopically but this time I had identified Phaeolepiota aurea with certainty and, however enticing it looked, had no need to remove it.

Arched Earthstar, Geastrum fornicatum

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Arched Earthstars. Geastrum fornicatum

A couple of Arched Earthstars. Geastrum fornicatum, 4th February 2024.

I’ve seen quite a few different earthstars and I’ve written about some of them on this blog – the Vaulted Earthstar (Geastrum britannicum), Collared Earthstar (Geastrum triplex) and the very localised coastal Dwarf and Tiny Earthstars (Geastrum schmidelii and Geastrum minimum). All are basiodiomycete fungi and members of the family Geastraceae.

Arched Earthstars in Norfolk

One species I hadn’t seen until recently was the Arched Earthstar, Geastrum fornicatum. But fungi can be like buses – you wait ages to see one and then two come along at once. Since the start of this month I’ve seen Arched Earthstars in two different places (note 2).

Arched Earthstars aren’t common in Norfolk and up until the end of 2023 were only known from 14 different sites.

My first sighting was on 4th February. Returning from a trip to a site just outside Norwich with our friends Sarah and Ian, Sarah stopped the car by our Vaulted Earthstar (Geastrum britannicum) site. I spotted an earthstar on the road verge and Vanna was about to say ‘Arched Earthstar’ but Ian got there a couple of seconds earlier. We then looked under the nearby Yew tree and Vanna counted 31 earthstars. They were all Arched Earthstars, Geastrum fornicatum, and we didn’t see any Geastrum britannicum.

Six days later Vanna and I cycled down to South Norfolk. It was a successful day – we had found a new site for Sandy Stiltball (Battarrea phalloides) on a road verge on our way south. We had lunch in a churchyard and found a couple of dozen Arched Earthstars beneath a Yew tree. There were several Yews but just one with earthstars underneath.

Identifying Arched Earthstars

The genus name for earthstars, Geastrum, comes from geo meaning ‘earth’ and aster meaning ‘star’. The fruitbody consists of an inner and outer wall (peridium): the inner peridium is the spore sac and the outer peridium splits to form rays in a star shape (note 2).

The specific name for the Arched Earthstar, fornicatum, means ‘arched’. Its red-brown rays are upright and push the spore sac upwards, giving the earthstar an upright (arched) appearance. The spore sac has a swelling on its underside, known as the apophysis.

The rays of an Arched Earthstar are attached to a basal cup of mycelium, a feature shared with the Vaulted Earthstar (Geastrum britannicum) and Rayed Earthstar (Geastrum quadrifidum) (note 3). Arched Earthstars are 4 – 8cm across when the fruitbody is expanded, with four to five rays. The peristome, the hole in the top of the spore sac, is not delimited, in contrast to that of G. britannicum (note 4).

If you find a group of earthstars, it is worth examining as many as possible, especially when they are old and weathered. The spore sac on the one pictured below is a bit damaged but its basal cup is intact; other fruitbodies had a spore sac in better condition but had become detached from their basal cups.

Arched Earthstar. Geastrum fornicatum

Arched Earthstar. Geastrum fornicatum

Distribution

Geastrum fornicatum is found in southern England and Wales and there is a single record on the NBN Atlas for Ireland. it is widespread elsewhere in Europe but uncommon (note 5). It also occurs in the United States, growing under Monterey Cypress in California and in Australia, “in litter under trees in dry woodlands and mallee scrub”.

‘Reminiscent of ballet dancers’

In the United States Geastrum fornicatum is sometimes known as the Acrobatic Earthstar and Pat O’Reilly on his First Nature website notes how “these earthstars do have silhouettes reminiscent of ballet dancers”.

In 1799 the English naturalist James Sowerby (1757 – 1822) wrote a book entitled “Coloured Figures of English Fungi or Mushrooms“. In it, he described how Geastrum fornicatum (then known as Lycoperdon fornicatum) resembled the human figure:

“So strange a vegetable has surprised many; and in the year 1695 it was published under the name of Fungus Anthropomorphus, and figured with human faces on the head. It is at first roundish; in ripening the head bursts through the two coats or wrappers; the inner wrapper, detaching itself from the outer, becomes inverted, connected only by the edges; the coats most constantly split into four parts.”

There are good photos of Geastrum fornicatum on the First Nature website.

If you’re interested in identifying more earthstars, the guide “How to identify British earthstars” by Phil Gates on the Discover Wildlife website describes some of the other species.

I also thoroughly recommend “Mushrooms and Toadstools of Britain & Europe – Volume 1” (2017) by Geoffrey Kibby, which has two pages of earthstar illustrations and shows the three species which have basal cups side by side. Kibby describes the habitat of Arched Earthstars as being on soil under broadleaved trees.

Finally, we found the Vaulted Earthstars we’d missed on 4th February. Last Saturday we cycled past our Vaulted Earthstar (Geastrum britannicum) site and looked a little further along the road under a different Yew tree. We found a few more Arched Earthstars and, happily, at least half a dozen Vaulted Earthstars too (note 6).

Vaulted Earthstar, Geastrum britannicum

One of the Vaulted Earthstars, Geastrum britannicum. 17th February 2024.

Notes

Note 1 – The phenomenon of buses arriving together is explored on Jason Cole’s blog and in this New Scientist article from 2009.

Note 2 – It is estimated that there are up to 120 species of Geastrum throughout the world.

Note 3 – I haven’t seen the Rayed Earthstar (Geastrum quadrifidum). There are two records for Norfolk, but from the days before the Vaulted Earthstar (Geastrum britannicum) was recognised as a separate species. Rayed Earthstar is small (just 1.3 – 3.7cm across), rather uncommon and is usually found under Beech trees (Fagus sylvatica) on calcareous soils in southern England.

Note 4 – There is a good diagram of what a delimited peristome looks like in the 2009 publication “The distribution and identification of earthstars (Fungi: Geastraceae) in Norfolk” by Tony Leech, Trevor Dove & Jonathan Revett. See figure 4. (Note that this paper was written before Geastrum britannicum was recognised as a separate species.)

Note 5 – Geastrum fornicatum is featured on page 1251 in Volume 2 of Laessoe and Petersen’s two volume “Fungi of Temperate Europe”. They describe it as “widespread in the nemoral zones, very rare”. (“Nemoral” refers to the vegetation zone of temperate forests in Eurasia.)

Note 6 – I also checked the spores from the Arched and Vaulted Earthstars I found on each occasion. Both have globose, warted spores but those of Arched Earthstar (Geastrum fornicatum) are 3.5 – 4.2 µm across and those of the Vaulted Earthstar (G. britannicum) are smaller, 3 – 3.8 µm across. Both measurements exclude the warts.