Milkcaps (genus Lactarius) are some of my favourite fungi. They have decent sized fruitbodies that come in a range of subtle but beautiful colours, in shades that belong on a rather exclusive paint colour chart. Milkcaps exude “milk” from their gills, the genus name, Lactarius, being derived from the Latin “lac“, meaning milk.

I always love to see a milkcap, and it’s even better when it’s a species I haven’t seen before.

The Whiskery Milkcap, Lactarius mairei, is a very attractive but rather rare fungus. This autumn I’ve been fortunate to see it twice in Norfolk.

First Sighting

My first sighting was a “twitch”, visiting a known site after someone had posted pictures of it on Facebook.

Whiskery Milkcap, Lactarius mairei. October 2023. Photo: Chris Lansdell.

The site was on the edge of the Norfolk Brecks by the edge of a minor road bordered by Pedunculate Oak trees (Quercus robur). I learnt about the milkcap in late October last year but the weather was rather wet and windy at the time, so I chose not to cycle the fifty miles from Norwich to visit it. Fortunately my friend Chris had managed to go and took some pictures.

Whiskery Milkcap, Lactarius mairei. October 2023. Photo: Chris Lansdell.

I was pleased when the milkcaps reappeared in late September this year in the same spot. The weather was dry and sunny and provided just the right conditions for a bike ride. I found the spot (marked by a rather pungent dog waste bin just a few yards away) and saw the fungi.

The fruitbodies were tiny, only just emerging from the dry ground. The photograph below shows the size of one of the caps, with a dead Ivy leaf for scale. In twitchers’ speak it was a “ticK’ but not the most beautiful or spectacular specimen.

Whiskery Milkcap, Lactarius mairei, September 2024.

A Chance Encounter

My second sighting was on Tuesday this week. Vanna and I had gone for a bike ride along the Yare valley west of Norwich and stopped in a churchyard for lunch.

On the way in Vanna found a single woolly pinkish buff cap lying on the grass: it was Lactarius mairei again. There was no sign of the stem.

Cap of a Whiskery Milkcap, Lactarius mairei.

I took a sniff of the cap and noticed a delicate, slightly fruity smell. Geoffrey Kibby describes the odour as “acidic-fruity of Pelargonium, to slightly oily” (note 1).

This time I was able to see the underside of the cap and the copious white “milk” that was oozing from the gills.

Whiskery Milkcap, Lactarius mairei, underside of cap.

Taste is a useful tool when identifying milkcaps. If you dab a bit of milk on your tongue, it can be mild or acrid (hot) or bitter. The idea is not to actually eat the fungus – you spit out any residue and, if it is hot or bitter, can rinse out your mouth with water.

The milk’s colour is useful too, and whether it changes colour after several minutes – best seen when a spot of milk is dabbed on a paper tissue. Species also differ in their milk’s consistency (from watery to thick) and how abundantly it is produced.

So I dabbed a little of the abundant, white milk on my finger and tasted it. I don’t mind heat but this was not only very acrid but left a very nasty taste, difficult to describe but very unpleasant and lingering. Luckily it was lunchtime and a couple of mouthfuls of peanut butter sandwich took the taste away (note 2).

Rare, with oaks

Whiskery Milkcaps form mycorrhizal relationships with oak trees and our specimen was beneath the spreading branches of a large Pedunculate Oak (Quercus robur). The fungus receives sugars from the tree, manufactured from sunlight by photosynthesis and in exchange it grows as an extension of the tree’s root system and provides the oak with water and minerals.

In Britain, Lactarius mairei is mainly found in southern England where oaks grow on calcareous soils. At the time of writing there are five records from Norfolk, from four different sites. The NBN Atlas has 38 records, all but one south of The Wash. The fungus is considered rare in Britain and is scarce in other parts of Europe too, appearing in several countries’ red data books.

The Whiskery Milkcap is usually found in September and October. The species was first found in Morocco and described for science by Georges Jean Louis Malençon in 1939. The specific name, mairei, is a tribute to the French botanist and mycologist René Maire.

I’m glad to have seen it. Next time I hope to see a full sized whole specimen, complete with stem. I might not taste the milk though.

Thanks to Chris Landell for allowing me to use his photographs.

Notes

Note 1 – “British Milkcaps: Lactarius and Lactifluus” (2016) by Geoffrey Kibby.

I also consult “Mushrooms and Toadstools of Britain & Europe – Volume 1” (2017) by Geoffrey Kibby and “The Genus Lactarius” by Jacob Heilman-Clausen, Annemieke Verbeken and Jan Vesterholt (1998) when I want to identify a milkcap.

Note 2 – The “milk” (also known as “latex”) is produced when the fungus is damaged and its function is probably to clog up the mouthparts of insects and other tiny animals that try to eat the fungus. Anecdotal evidence supports this theory – I find that milkcaps’ close relatives the Brittlegills (Russula spp) have usually been nibbled by slugs, while milkcaps remain intact.

Given my experience of the milk’s taste, if I am reincarnated as a slug I will think twice before eating a Whiskery Milkcap!