Nail Fungus, Poronia punctata

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Nail Fungus, Poronia punctata

Nail Fungus, Poronia punctata, at Buxton Heath.

At the end of April a group of us visited Buxton Heath, just north of Norwich. We had mainly gone to look for insects but it was a cold day with light rain and, apart from some dung beetles, most of the insects we’d hoped to see had sought shelter.

Nonetheless, we had a good walk and up on the drier heath I was very pleased to find something I hadn’t seen before: Nail Fungus, Poronia punctata. It is a very distinctive species, which looks rather like one of those flat-headed nails used to fix bituminous roofing felt to the roof of a garden shed. The First Nature website has some great photographs. The cap of the fungus has distinctive pores, hence the generic name, Poronia.

Nail Fungus appears in autumn but persists through winter into spring. It can be found growing on dung in open areas, such as grassland and heathland, where ponies graze. It is an ascomycete in the family Xylariaceae, and therefore is a relative of Cramp Ball (King Alfred’s Cakes, Daldinia concentrica), which I wrote about last May.

In Britain Nail Fungus grows on pony dung but in other parts of the world it has also been found on the dung of cows, sheep and elephants.

Nail Fungus is a declining species in Britain and throughout the world. At the time of writing it was being assessed for the Red Data List for fungi. Its decline is due to the reduction of natural and semi-natural grasslands and the use of agrochemicals, pesticides and veterinary additives. In her MSc thesis Nicola Edwards studied the fungus at Hockwold Heath and Cranwich Camp in Norfolk, and found that dung needed to be damp enough and have a reasonable amount of dung beetle activity for the fungus to grow (note 1).

Poronia punctata is a UK Biodiversity Action Plan species. The NBN Atlas lists 198 British records and shows its distribution in the British Isles. A century ago it was quite common but it declined until The New Forest in Hampshire was one of its last strongholds. Now that ponies are being used more widely for conservation grazing the species is cropping up more frequently again and it has been recorded from Dorset, Hampshire, Surrey and even London. In Poland, the species was rediscovered in 2016, after an absence of a hundred years.

In Norfolk Nail Fungus was rediscovered in Thetford Forest in 2012, the first record for the county since 1944. It has been seen a few times since then, including by James Emerson at Holt Lowes last autumn (note 2). It was good to have seen Nail Fungus on Buxton Heath.

Nail Fungus is considered to be inedible. Even if it wasn’t rare, Nail Fungus would not be a species for fungal foragers, as it is small and grows on dung. As the First Nature website says: “who would even want to try eating them?“. However, some scientists are interested in the fungus because it contains a number of bioactive compounds, including a group of sesquiterpenes known as punctaporonins, which inhibit the growth of competing bacteria and fungi in dung.

Notes

Note 1 – See “Does Breckland vegetation and its management influence abundance of Poronia punctata?“, Nicola Edwards, MSc thesis, Sparsholt College, 2015.

Nicola found that the anthelmintic drug pyrantel wasn’t detrimental to the fungus, presumably as it didn’t reduce the number of dung arthropods. However, elsewhere, the anthelmintic drug ivermectin has been implicated in the decline of dung beetles, which will presumably have a knock-on effect on Nail Fungus.

I’m glad to say we found good numbers of Minotaur Beetles on Buxton Heath when we visited.

Note 2 – Nail Fungus was plentiful at Holt Lowes when I visited at the end of October 2019.

Purple Toothwort, Lathraea clandestina

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Purple Toothwort - Lathraea clandestina

Purple Toothwort – Lathraea clandestina

A few weeks ago my friend Chris Lansdell asked me where he could find Moschatel in the local area and I gave him details of a couple of sites, including at Natural Surroundings at Bayfield. As a “thank you” he told me that the Purple Toothwort was in flower at Bowthorpe, on the western outskirts of Norwich. I was originally told about the plants a couple of years ago, but didn’t make the trip to see them. This time, I decided I would go and I’m glad I made the effort (just a fifteen minute cycle ride from home). The plants were growing on a bank in a shady spot underneath some Willow trees.

Purple Toothwort, Lathraea clandestina is a low growing, perennial plant that is parasitic on the roots of various trees, especially Poplar (Populus) and Willow (Salix). Other plants may be used too, including  Acer (Sycamore / Maples), Alder (Alnus), Box (Buxus), Hornbeam (Carpinus), Hazel (Corylus), Walnut (Juglans), Metasequoia, Rhododendron, Yew (Taxus) and Gunnera. The plant can be found in the damp shady places where its hosts grow.

Purple Toothwort is a member of the family Orobanchaceae, along with Broomrapes (such as Purple Broomrape and Ivy Broomrape), Eyebrights, Yellow Rattle and Red Bartsia. Like the Broomrapes, Purple Toothwort has no chlorophyll and relies on food taken from its host. It bears small, simple scale leaves on alternate sides of its stem and its very pretty purple flowers shoot upwards from the stems, appearing from March to May. These develop into explosive seed capsules later in the summer.

The plant is hardy but early flowers may sometimes be damaged by frost. It is a fairly recent introduction to the British Isles (a neophyte). It was brought into Britain as an attractive garden curiosity and was planted at Kew Gardens in 1888. It was first reported from the wild in 1908 at Coe Fen in Cambridgeshire, where it was probably deliberately planted. It can still be found there. Purple Toothwort is found in various parts of England and Wales, with a few outlying colonies in Scotland and Ireland. Its native home is across the English Channel in Belgium, France, Spain and Italy.

Purple Toothwort flowers are pollinated by bumblebees. I saw a single Tree Bumblebee (Bombus hypnorum) worker when I made my visit, but it was flying just above the flowers, rather than venturing inside. The flowers have very alkaline nectar, which tastes of ammonia, though I only found this out after my visit. The taste or alkalinity is thought to deter birds and ants from robbing the nectar from the flowers without pollinating them.

There are several other species of Lathraea in Europe, all parasitic and lacking chlorophyll. In Britain we have one native species, Toothwort, Lathraea squamaria. It usually uses Hazel (Corylus) as a host, but can sometimes be found on Elm (Ulmus), Ash (Fraxinus), Alder (Alnus), Walnut (Juglans) and Beech (Fagus). One grows at Kew Gardens, under a Black Walnut tree. Further afield Toothwort grows as an annual or perennial in lowland deciduous woodland, in hedgerows, and on the banks of rivers and streams. It has white or creamy to pinkish-purple flowers, produced from March to May. I have yet to see it, as it is more or less absent from East Anglia.

The generic name Lathraea comes from the Greek word lathraios, meaning hidden. Clandestina means secret (clandestine). Both words relate to Purple Toothwort’s habit of hiding in dark corners though, as I found on Tuesday, this beautiful vampire is well worth seeking out.

Purple Toothwort, Lathraea clandestina

A patch of Purple Toothwort, Lathraea clandestina.

Mimosa, Acacia dealbata

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Mimosa, Acacia dealbata

Our very mild late winter and spring has suited tender plants, such as Mimosa, Acacia dealbata. There are several Mimosa trees in Norwich and they have been flowering for weeks now, lighting up front gardens with the bright yellow puffs of their flowers. As I write, some of the flowers are beginning to turn brown with age, but from a distance the effect is still magnificent. Close up, the flowers have a delicious scent. The Fragantica website describes this as a “child-like, sweet, soft and hazy heliotrope-smelling note with sugar-spun tonalities”. Mary Keen describes the scent as the “smell of southern spring“.  They smell nice, anyway.

Acacia dealbata is a native of southeastern Australia (New South Wales, Victoria, Tasmania and the Australian Capital Territory). It was introduced into Southern France in 1820 and is now widely planted and naturalised in many parts of the world with a suitable climate, including other parts of Australia, the Mediterranean region from Portugal to Greece and Morocco to Israel, the Black Sea coast of Russia, Ukraine, California, Madagascar, South Africa, Zimbabwe, the highlands of southern India, south-western China and Chile. It can be a serious weed in New Zealand and parts of South Africa.

Mimosa is a member of the Fabaceae, the Pea family. Other English names include Silver Wattle and Blue Wattle. In its native land Acacia dealbata is a pioneer species that colonises after a bush fire. The roots have nitrogen-fixing bacteria in their nodules, and can bind together soils to prevent erosion. Mimosa grows rapidly to about 30 metres (100 feet) tall but seldom lives longer than thirty to forty years. In the UK, it is more likely to reach 8 – 12 metres (26 – 40 feet) tall and frost, rather than natural causes or fire, is likely to end its life.

In the UK, growing Mimosa is often a bit of a gamble and “probably not something to try out of doors north of the Trent“. It can survive brief cold spells down to -10°C, but it is officially given a hardiness rating of H3 by the RHS: Hardy in coastal and relatively mild parts of the UK (-5 to 1°C).  It would probably not survive a cold winter like 2009 and 2010, though most winters are now milder in the south of England.

Shrubs such as Leptospermum are equally tender but small enough to cover in the winter, whereas Mimosa can become too tall to wrap up against the chill. It is most likely to survive in a sunny, sheltered spot in well-drained soil. If cut down by frost, it may regrow as a multi-stemmed shrub. If you need to prune your Mimosa, follow the RHS instructions for Early flowering evergreen shrubs (pruning group 8) – prune after flowering.

Acacia dealbata subspecies ‘Subalpina’, which grows at higher altitudes, is a bit hardier than the wild type and said to be worth seeking out: at the time of writing it is stocked by Shoot. James Wong mentions a related dwarf form, Acacia nanodealbata (sometimes spelt nono-dealbata). Anna McKane describes some other hardy (ish) Acacia species in her 1996 article in The Independent, “On the trail of hardy mimosas“.

Mimosa trees can be raised from semi-hardwood cuttings or from seed, though the seeds need to be treated with boiling water and then left to soak for a day. The boiling water mimics the heat of a fire that would trigger germination in the wild.

The Plants for a Future website tells us that Mimosa gum (which exudes from the trunk) is edible, and can be used as a substitute for gum arabic. The real thing comes from two close relatives: Senegalia senegal (Gum Acacia) and Vachellia seyal (Red Acacia).

Mimosa flowers are often sold by florists. The flowers are edible when cooked and according to Plants for a Future can be made into fritters, although the recipes I found when searching for “Acacia flower fritters” used the white flowers of the related Black Locust tree,  Robinia pseudoacacia.  Mimosa can be used as a dye plant, either for yellow (the flowers) or green (the seed pods).

Mimosa Salad sounds appetising, but no Mimosa was harmed (or used) in making it. A festive salad in the former USSR, its main ingredients are cheese, eggs, canned fish, onion, and mayonnaise. If boiled egg yolk is crumbled and scattered on its surface, it is said to resemble mimosa flowers scattered on snow.

Mimosa, Acacia dealbata

Mimosa against a blue March sky.