Sweet Briar Marshes

Sweet Briar Marshes is a 90 acre Norfolk Wildlife Trust nature reserve in Norwich, purchased in 2022 after a public appeal and officially opened in spring 2024.

The reserve is crossed by Sweetbriar Road, part of Norwich’s busy outer ring road, with a third of the land area on the east side, nearer the city centre, and the other two thirds to the west. The eastern portion includes a Site of Special Scientific Interest (SSSI). Much of the western part of the reserve was arable farmland until as recently as the 1990s.

The reserve has contrasting wet and dry areas. The wet areas, nearer the River Wensum, consist of fen and grazing marsh with wet woodland and slightly higher wooded islands.

Wooded island and fen, Sweet Briar Marshes, October 2025

The dry higher ground is mainly rough meadows with scattered hawthorn and broom bushes, with old hedgerows and younger woodland.

One of the main paths at Sweet Briar Marshes, August 2025. The surface allows access for wheelchair users and the raised curb (seen on the right) was installed to provide a landmark for partially sighted visitors.

There are some lovely veteran oaks and woodland pools which can be full of water or completely dry, depending on how much rain has fallen.

In a wet winter (such as 2023 – 24) the wet areas are very, very wet, drainage dykes are impassable and the river floods onto the lower lying parts of the reserve, but at the time of writing the whole reserve is very dry and the woodland pools are empty of water.

Fen in August 2024, with flowers of Water Mint & Common Fleabane.

As a member of Norfolk and Norwich Naturalists Society (NNNS) I’ve been able to visit areas of the reserve not normally accessible to the public, as part of a two year project to record wildlife, plants and fungi on the reserve. My wife Vanna and I also lead guided walks on the reserve, Vanna looking at insects and other invertebrates, while I lead fungal forays.

Recording Fungi at Sweet Briar Marshes

I started to look at Sweet Briar Marshes fungi in 2023. Norfolk Fungus Study Group has visited twice and other records have been submitted by individuals, including members of the British Mycological Society (BMS), who visited as part of their spring field meeting in March 2025.

Norfolk Fungus Study Group’s visit to Sweet Briar Marshes October 2024. Cows graze the reserve and there are a couple of fresh cowpats in the photograph at the bottom left.

The current official tally is 275 species of fungi, but we’ve added quite a few species since then, so the true number must have easily reached 300 species.

Five Fungi from Sweet Briar Marshes

Here are accounts of five of the fungi I’ve found at Sweet Briar Marshes.

They’re not always the prettiest but, with the exception of Birch Knight, they were all new species for me, and sometimes for Norfolk.

1. Birch Knight, Tricholoma fulvum

The Birch Knight, Tricholoma fulvum, isn’t a rare fungus and is described as “very common and widespread throughout Britain and Ireland“. But the woodland needs to be wet and you need to visit its habitat at the right time to be lucky enough to see it.

I’d only seen it once before, at Broadland Country Park in November 2021, so I was very pleased to encounter it on this Tuesday’s public foray at Sweet Briar Marshes. It was growing beneath a Silver Birch tree on one of the small wooded islands, a new species for the reserve.

Three picked fruitbodies of Birch Knight, Tricholoma fulvum.

Birch Knight, Tricholoma fulvum, in situ.

The fungus has a reddish-brown cap, often with radial brown streaks, and bright yellow, adnexed gills that become marked with brown spots as they age.

Three picked fruitbodies of Birch Knight, Tricholoma fulvum. Note the adnexed gills marked with brown spots.

Birch Knight forms an ectomycorrhizal relationship with birch trees, supplying the tree with water and minerals in exchange for sugars, which the tree manufactures by photosynthesis. Other partners include Beech (Fagus sylvatica) and oaks (Quercus) and firs (Abies) and spruces (Picea).

2. Hypholoma subericaeum

Fungi growing in the bottom of a dried up drainage dyke: Hypholoma subericaeum

On a visit to Sweet Briar Marshes last Saturday I found a mass of moderately sized fungi growing amongst plant remains at the bottom of a dried up drainage dyke. They were rather lovely, with perfect very round caps. They were clearly something I hadn’t seen before, so I picked them and took them home. I consulted several books, looked at some websites and did some microscopy and finally decided they were Hypholoma subericaeum. (There are similar species with larger spores.)

Three picked fruitbodies of Hypholoma subericaeum.

The fungus doesn’t have an English name but its German name, Teichrand-Schwefelkopf, translates as the very appropriate Pond-edge Sulphur Cap. Its habitat is described as “Saprobiotic on the banks of drying, stagnant waters on rich, putrid mud soils between pioneer plants and old herb roots.” There are seven previous records for Hypholoma subericaeum in Norfolk, on wet soil.

Hypholoma subericaeum is a relative of the much more familiar Sulphur Tuft, Hypholoma fasciculare, which is also saprotrophic. It grows on dead tree stumps and breaks down the wood to obtain its food.

Young Sulphur Tufts, Hypholoma fasciculare, on a mossy tree stump.

3. Lakeside Webcap, Cortinarius lacustris

In October 2024, on a fungal foray, Vanna and I spotted a group of fungi near the edge of one of the wooded islands on the marsh, under a  Pedunculate Oak (Quercus robur). On closer inspection they were a species of webcap (Cortinarius), a genus of  fungi that forms mycorrhizal relationships with trees.

Young fruitbodies of webcaps have a cap encased in a cobweb-like veil, a protective covering known as a cortina (note 1). Traces are left behind on the stem and cap of the fruitbody and their colour provides important clues to the identity of the fungus.

Identification of webcaps is very tricky, as there are lots of species, many of which look very similar. Thankfully, there is now a good field guide, “The genus Cortinarius in Britain” by Geoffrey Kibby and Mario Tortelli (2021) which makes the task possible, if not easy.

Lakeside Webcap, Cortinarius lacustris

We were leading a public foray at the time so returned the following day to collect some fruitbodies for a DNA sample. I  keyed out the fungus in the Kibby and Tortelli book and provisionally identified it as the Lakeside Webcap, Cortinarius lacustris.

Picked fruitbodies of Lakeside Webcap, Cortinarius lacustris. The young fruitbody on the left has a white veil. The smell was fainly earthy or raphanoid (like radishes).

I was very pleased when DNA analysis by the Norfolk Fungus Study Group’s DNA Team confirmed that my identification was correct (note 2). This was a new species for the county and, at the time of writing Sweet Briar Marshes is the only known Norfolk site for Lakeside Webcap, Cortinarius lacustris. The species is described as “widespread in Britain” in deciduous woods, so more likely to have been overlooked than be a genuine rarity.

4. Lemonbalm Webcap, Cortinarius pilatii 

A year earlier, in October 2023, we found a group of webcaps in another area of deciduous woodland on the reserve.

They had a very pleasant scent, of Pelargonium mixed with roses, which usefully narrowed them down to one of a small group of webcaps with this type of smell. I provisionally identified them as Lemonbalm Webcaps, Cortinarius pilatii. DNA analysis confirmed my identification.

A small group of Lemonbalm Webcaps, Cortinarius pilatii.

Picked fruitbodies of Lemonbalm Webcap, Cortinarius pilatii.

I found the fungi in the same place last year and a week or two later at Broadland Country Park, north of Norwich. Geoffrey Kibby added another Norfolk record, from Litcham Common, in November 2024. Described as “widespread and rather common” they are probably in many woods, but overlooked.

5. Poplar Fieldcap, Cyclocybe cylindracea

On our October 2024 public foray we had a look at a fallen poplar tree on the reserve. We’d found Yellow Shield, Pluteus chrysophaeus and Flame Shield, Pluteus aurantiorugosus, there previously, two colourful saprotrophic wood decaying fungi.

This time something bigger was growing on the tree: Poplar Fieldcap, Cyclocybe cylindracea. It grows in clumps on dead or dying trunks or stumps of poplar (Populus) and willow (Salix) and also on hardwood woodchips.

Young Poplar Fieldcaps, Cyclocybe cylindracea.

Older Poplar Fieldcaps, Cyclocybe cylindracea.

Poplar Fieldcaps have a distinctive ring on the stem, which is obvious in the two picked fruitbodies below:

Picked Poplar Fieldcap fruitbodies, Cyclocybe cylindracea.

I hadn’t seen Poplar Fieldcaps before, so I was very pleased to see them. They’ve been found at Whitlingham, near Norwich, but most recent records have been in the west of the county. More fruitbodies appeared on the same tree in August 2025, after some rain.

Cyclocybe cylindracea has been cultivated since the time of the early Greeks and Romans and it is a good edible species. I took home a couple of fruitbodies to confirm their identity and I later cooked, ate and enjoyed them. But fungi provide a valuable habitat so I did the right thing and left most of the fruitbodies in place (note 3).

Notes

Note 1 – A cortina on a Cortinarius gives the genus its name. It has nothing to do with the Ford Cortina, my parents’ first car, which was produced from 1962 to 1982 and named after the Italian ski resort Cortina d’Ampezzo, the site of the 1956 Winter Olympics.

Note 2 – I have submitted quite a few samples of Cortinarius and other difficult to identify fungi for DNA analysis. My provisional identifications often turn out to be wrong, though we’ve found some interesting new species for Norfolk. But the fungi I choose for DNA analysis are difficult – and that’s the reason to check.

Note 3 – Fungal fruitbodies provide a habitat for for a wide range of invertebrates, including mites, springtails, beetles and the larvae of flies.

One of my biggest surprises this year came when I was about to cut a gill of a fungus I’d brought home from the Norfolk Brecks to look at under the microscope. A black and red rove beetle, some 20mm (0.78 inches) long, suddenly appeared from between the gills and I don’t know who had the bigger shock!

It was Oxporus rufus, a species that lives in decaying fungi. They are omnivorous and sometimes hunt for small insects.

I returned the beetle to the wild a couple of days later, during which time it had cut the gills with its powerful jaws and made a chamber where it could hide.

Beautiful and distinctive rove beetle, Oxyporus rufus, emerging from the rotting remains of a fungus. I took this photo when I returned the beetle to the wild.