Foraged

Lactifluus corrugis and L. volemus: delicious wild mushrooms

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Corrugated milk cap mushrooms (Lactifluus corrugis) and Bradley milk caps (Lactifluus volemus) are two closely related species of edible mushrooms in the Russulaceae family. Both are edible, delicious, and commonly found in the summertime in temperate climate forests throughout the world, including North America. 


Milk cap mushrooms? Watch the quick video below for a quick introduction to corrugated milk cap mushrooms — and you’ll also see why various species of fungi are commonly called “milk caps”: 

 

*Note: Video may not play if you run ad blocking software. 

Mushroom visual identification vs genetic analyses  

We don’t want to dive too far into the weeds and make your eyes glaze over talking about mushroom taxonomy, but there are some important realities that we want to share if you’re interested in foraging mushrooms… 

Sometimes, a 100% certain identification of a mushroom species is nigh impossible. That’s partly because modern molecular phylogenetic analyses has caused — and continues to cause — many mushroom species to be reclassified and renamed. It’s also partly because those same modern genetic tools are causing us to recognize that there may be a lot of subspecies and varieties underneath the umbrella of what was once thought to be a single species based purely on visual analyses.

We’ve come a long way since Linnaeus when it comes to categorizing the natural world — and we still have a long way to go.  

A corrugated milk cap mushroom (Lactifluus corrugis) pushes through the leaf litter on the forest floor.

A corrugated milk cap mushroom (Lactifluus corrugis) pushes through the leaf litter on a forest floor.

 

Genetic diversity in Lactifluus volemus and Lactifluus corrugis

Case in point: Lactifluus volemus and Lactifluus corrugis, *two relatively common summer mushrooms found in temperate climate forests around the world. Turns out, these species are far more diverse than once thought.

Light trickling through the forest canopy on to the cap surface of a corrugated milk cap mushroom.

Sunlight trickles through the forest canopy on to the cap surface of a corrugated milk cap mushroom.

For instance, a 2007 study of Chinese Lactifluus volemus and L. corrugis concluded: 

Analyses of nucleotide sequence, fatty acid composition, morphological characteristics, and the taste of the fruiting bodies all led us to conclude that the common, velvet, red, and Chinese types of L. volemus, and the common and red types of L. corrugis, may each belong to different species, subspecies, or varieties. Further studies with more material from a wide range of regions are required to conduct taxonomic revision of these types. The LSU rDNA region may be a useful tool to investigate phylogenetic relationships within the section Dulces of the genus Lactarius.

Life on earth is not genetically static. Genetic dynamism allows for the massive biodiversity we see today, and that diversity in turn allows life to have a better chance at optimizing itself (surviving and reproducing) within the specific environments in which each new generation finds itself. 

If you’re a mushroom forager, this simply means that seemingly minor differences in fungal morphology could potentially indicate that you’re looking at a genetically distinct subspecies or variety — especially if they’re growing in different regions or associating with different tree species. Perhaps such fungi might also be part of a species complex or cryptic species

While we're comfortable calling these corrugated milk cap mushrooms (Lactifluus corrugis), it's entirely possible that there are distinct subspecies and varieties within our forests.

While we’re comfortable calling these corrugated milk cap mushrooms (Lactifluus corrugis), it’s entirely possible that there are distinct subspecies and varieties within our forests that could be revealed by genetic analysis.

  

“Bradley” lactarius 

When The Tyrant and I first started foraging mushrooms a decade ago, we learned to be on the lookout for “Bradley lactarius” mushrooms in the summer.

A summer hike on this trail near Greenville, SC, easily yielded a basket full of edible milk cap mushrooms.

A summer hike on this trail near Greenville, SC, easily yielded a basket full of edible milk cap mushrooms.

Keys to identifying these mushrooms:

  • common in summer in mixed growth forests (hardwoods and coniferous trees);
  • rusty, reddish colored caps;
  • light colored gills and stems;
  • white latex “milk” oozes from the caps, stems, or gills when cut; latex and cut marks soon turn brown;
  • white spore print;
  • distinct fishy smell which increases after harvest (which is not at all indicative of their taste after cooking).
A closer look at the latex emerging from a scrape on the gills of a corrugated milk cap mushroom. This specimen is young and has relatively dark gills.

A closer look at the latex emerging from a scrape on the gills of a corrugated milk cap mushroom. This specimen is young and has relatively dark gills.

Since there aren’t any poisonous lookalikes in our area that match those characteristics, we filled up many a harvest basket with what we simply called “Bradley lactarius” mushrooms.

The underside of 'Bradley' milk cap (Lactifluus volemus). You can see some of the telltale morphological differences in this specimen versus the corrugate milk cap mushroom pictured in the photo above this one.

The underside of a young Bradley milk cap mushroom (Lactifluus volemus). You can see some of the telltale morphological differences in this specimen versus the corrugate milk cap mushroom pictured in the photo above this one. More on species distinction below… 

“Bradley” (which likely comes from the German word Brätling) is just one of many common names on a long list, including: 

  • apricot milk cap
  • fishy milkcap
  • lactarius orange
  • leatherback
  • orange-brown milky
  • tawny milkcap
  • voluminous-latex milky
  • weeping milk cap.

If all of those common names seem confusing, perhaps you’ll appreciate taxonomy and universal scientific names. But when even the scientific names get reshuffled, things can get even more confusing. 

Due to genetic analysis, our “Bradley lactarius” which were once classified as Lactarius volemus, were reclassified to Lactifluus volemus in 2008 (still in the Russulaceae family). And as we’ve recently come to find out, many of the mushrooms that we once thought were Bradleys were actually corrugated milk caps (Lactifluus corrugis), a close relative.    

Visual differences between Lactifluus corrugis and L. volemus

Both L. corrugis and L. volumus are edible fungi that fruit at the same time in the same place and associate with the same tree species. They look very similar and produce the same fishy smell. Both produce a white spore print. 

So how do you tell the two species apart? 

  • Lactifluus corrugis has a whitish, felt-like appearance on the cap surface, which is especially prominent when the mushrooms are young (and less visible after a rain when the caps are wet). L. volemus does not have a felt-like appearance on the cap surface.
  • As the name implies, the cap surface of L. corrugis is heavily corrugated, with the appearance of wrinkly leather with indentations. L. volemus’s cap surface is much smoother. 
  • Some sources say L. corrugis has a redder-colored cap and slightly darker gills than L. volemus. However, we see fairly wide variability in the intensity of coloring on the gills and caps of both. Perhaps this trait varies by subspecies. 
Bradley milk cap mushrooms (Lactifluus volemus).

Bradley milk cap mushrooms (L. volemus).

Lactifluus spp. role in forest ecosystems 

Lactifluus is one of three genera of mushrooms that are commonly referred to as “milk caps,” the other two being Lactarius and Multifurca. They’re called milk caps due to the sticky latex they emit when cut or nibbled — a defense against slugs and other critters that eat them. 

You’ll typically see other milk cap mushrooms — which range from edible to poisonous to technically edible but not tasty — fruiting at the same time as Lactarius volemus and L. corrugis

What do Lactifluus mushroom species do in a forest? Feed trees water and nutrients in exchange for the tree feeding them sugars made via photosynthesis. 

Lactifluus are ectomycorrhizal, meaning the fungi form a protective sheath over the host tree’s roots, with fungal hyphae extending out into the soil beyond the roots’ reach. There, the fungal hyphae mine and bring nutrients and water back to the tree.

Where the tree roots and fungi interface, ectomycorrhizal fungi form a Hartig net, branching around and in between the outer surface layers of the root cells, where nutrients are exchanged between the two organisms. This is distinct from endomychorrhizal mushroom species which actually penetrate tree root cells to exchange nutrients. 

In short, Lactifluus fungi species enhance the health of individual trees and the resilience of forest ecosystems. And you get to enjoy the “fruit” of all that interspecific cooperation when you pick and eat the edible species within the genus!  

When harvesting, just be sure to use a breathable bag or basket so you spread the spores far and wide as you go. 

How to eat Lactifluus volemus and Lactifluus corrugis

Don’t worry, Lactifluus volemus and corrugis might smell like fish when they’re raw, but they don’t have any fishy flavor at all once you cook them. And the sticky latex is quickly broken down by heat. 

The flavor of these two milk cap mushrooms is richly fungal and delicious; umami. They also maintain a very firm meaty texture, perhaps due to having a higher protein content than many other mushrooms.  

If you’re a vegetarian or vegan, you can use them as a meat substitute in dishes. Since we eat ethically raised meat and these two species are among a handful of mushrooms we know of that go well with beef, we usually use them on top of a grass-fed burger or steak. 

A few of the toppings we use to make the perfect burger: Sylvetta arugula, corrugated milk cap mushrooms, and caramelized onions.

A few of the toppings we use to make the perfect burger: Sylvetta arugula, corrugated milk cap mushrooms, and caramelized onions.

We slice the mushroom caps and stems, then put them in a cast iron pan on medium heat with enough water added to just cover the mushrooms. We also add a little salt and butter to the pan. The water cooks the mushrooms evenly without scalding them, while breaking down the chitin in the cell walls, making the nutrients in the cells available for digestion.  

Once the water cooks out, the fat from the butter helps keep the mushrooms from sticking to the pan. Then we just let the milk cap mushrooms cook for another 5-10 minutes, flipping and stirring them every minute of so until they’re nicely browned. The spores emitted from the cooking mushrooms into the water are reabsorbed by the mushrooms turning them a dark brown/black color.      

From there, you can eat your milk cap mushrooms as-is, use them as a topping, or add them to another dish like an omelette. 

The cooked L. corrugis mushrooms photographed in this article went on top of grass-fed burgers that The Tyrant and I enjoyed after a long hike in the woods. We usually see who can make the best milk cap mushroom burger then bicker about who won. Other than milk cap mushrooms, toppings include caramelized onions, Sylvetta arugula and fresh tomatoes from our garden, and ketchup and mustard.

My burger topped with cooked, corrugated milk cap mushrooms. Clearly superior to the burger shown below...

My burger topped with cooked, corrugated milk cap mushrooms. Clearly superior to the burger shown below…

The Tyrant's burger topped with cooked, corrugated milk cap mushrooms.

The Tyrant’s burger topped with cooked, corrugated milk cap mushrooms.

In my opinion, I was victorious, but The Tyrant and I were unable to reach a consensus.  

KIGI,

More fungal fun from Tyrant Farms:

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