Blue mushrooms? How to find & eat indigo milk cap mushrooms!

Last Updated on August 3, 2022 by Aaron von Frank

Indigo milk cap mushrooms (Lactarius indigo) are beautiful vibrant blue mushrooms that are also edible. In this article, you’ll learn how to find, identify, and eat indigo milk cap mushrooms.

Intro video: indigo milk cap mushrooms, bright blue mushrooms you won’t believe are real

(*Indigo milk cap video may not play if you are running ad blocking software – temporarily disable to view.)

Safety disclaimer:

For both legal and practical reasons, any foraging articles we write also come with a warning… As detailed in our article Beginner’s guide to foraging, rule #1 is: Never eat anything you’re not 100% certain you’ve correctly identified AND you’re not 100% certain is edible. There are plenty of plants and mushrooms that can kill you or make you very sick.

Now, on to indigo milk cap mushrooms (Lactarius indigo)! 

We’ve been foraging for gourmet wild mushrooms since 2010. Living at the base of the Appalachian Mountains in Greenville, South Carolina puts us in the heart of one of the best hiking and mushroom foraging regions in the US.

Two delicious rare wild-foraged mushrooms: Black trumpets (Craterellus fallax) and Umbrella polypore (Polyporus umbellatus) growing next to each other in late summer.

Outside of gardening, foraging mushrooms and plants is our favorite outdoor activity. It’s like going for a treasure hunt, but we get to eat the treasure at the end of the day. Even better, we get to exercise while learning about the amazing interspecific relationships that are taking place all around us.

Case in point: indigo milk cap mushrooms (Lactarius indigo), which fruit in our area (Upstate South Carolina) from late summer through fall. These vibrant, blue-colored mushrooms aren’t just visually stunning, they’re also edible to humans and beneficial to the trees with which they are symbiotic/mycorrhizal. 

Bright blue indigo milk cap mushrooms in our foraging basket.

What exactly is a mushroom and what role do indigo milk cap mushrooms play in a forest ecosystem?

Many people don’t realize that mushrooms are just the small fruiting bodies of very large organisms, similar to apples growing on a tree.

How large can mushrooms get? Well, the largest living organism on earth is a four square mile wide honey mushroom. That’s pretty big! 

Fruiting honey mushrooms (which are parasitic to trees) in the woods behind our home in the fall. What we see on the soil surface is just a tiny fraction of the overall mass of a much larger organism. 

Fungi play a critical role in maintaining the health of ecosystem’s the world over. For instance, every inch of soil in a forest is loaded with various species of fungi, some of which help form the “internet” of the forest, connecting trees together into a resource- and information-swapping network that survives more through collaboration than competition. 

Indigo milk cap mushrooms are one such fungal species that serves to help their host trees gain access to more nutrients and water while also connecting them to other trees in the “wood wide web.” In exchange, the trees feed the milk cap mushrooms carbohydrates which they produce through photosynthesis.

Other species of fungi aren’t so friendly to trees. These saprobic and parasitic fungi infect sick and dying trees, hastening their death, after which other species of decomposing mushrooms come in to help recycle the tree’s components back into soil/bioavailable nutrients.

Thanks to fungi, there is no waste in a forest system – everything is reused and recycled. In fact, if modern fungi species had been around during the Carboniferous period, we’d have almost no fossil fuels today, because the mushrooms would have consumed the wood and plant materials that would eventually form our coal and oil deposits.

It’s hard to imagine how different human civilization might be if fossil fuels had never been a possible energy source! 

How to find and identify indigo milk cap mushrooms (Lactarius indigo)

It’s important to note that indigo milk cap mushrooms can be found around the world, not just in North America. It’s highly likely that there are different subspecies of this fungi in different bioregions or even within the same region (which might help explain the flavor variability). 

A closer look at the gill side of indigo milk cap mushrooms (Lactarius indigo).

That means indigo milk cap mushrooms in our region (southeast US) most certainly fruit at a different time of year and form associations with different tree species than their cousins in other parts of the world. 

Thus, the identification information below pertains only to indigo milk cap mushrooms in the Southeast US.

When do indigo milk cap mushrooms fruit? 

In the Southeast US, indigo milk cap mushrooms fruit from late summer through early fall. The earliest we’ve ever found them is July and the latest we’ve ever found them is October. 

Where can you find indigo milk cap mushrooms? 

Indigo milk cap mushrooms can be found growing in mature hardwood or mixed forests. We’ve only ever found them associating with hardwood trees (primarily oaks and beech trees), but we’ve seen reports of them being found in coniferous forests in other regions of the country. 

7 key identifying features of indigo milk cap mushrooms: 

1. Blue-grey in color; brightest color when they’re young to mature, fading to grey as they age.
2. Blue-colored latex emerges when mushrooms are cut or scraped. The blue color oxidizes to green over time.  
3. Grow individually or in small groupings in leaf litter, emerging from hyphae on the underground roots of host trees.
4. Mature size of caps ranges from 2-6″ depending on environmental conditions. 
5. Young caps are convex turning concave as they mature. 
6. Distinct attached gills; no veil. 
7. Spore print is creamy. 

Are there poisonous lookalikes to indigo milk cap mushrooms? 

For the uninitiated forager, there are blue/purple species of poisonous Cortinarius that might be mistaken for indigo milk cap mushrooms. Once you’ve seen both types of mushrooms, they’re hard to mistake.

The two easiest ways to tell indigo milk caps and Cortinarius mushrooms apart:  

1. Cortinarius species do NOT emit any latex when cut or scraped; indigo milk caps emit a *bright blue latex when cut or scraped (*see video at top of article). 
2. Indigo milk caps produce a cream-colored spore print; Cortinarius have a rusty brown-colored spore print. 

If you want to dig deeper into Cortinarius mushrooms, check out their profile on Mushroom Expert. 

The inside of the Indigo Milk Caps is also bright blue, and will drip a bright blue latex when cut. The blue color of Lactarius indigo is due to an organic compound called “methyl stearate,” which is unique to this species.

What do indigo milk cap mushrooms taste like?

The flavor of indigo milk caps mushrooms varies more than most other edible mushrooms. This flavor variability may be due different subspecies. Or it could also depend on other factors such as the tree species they’re associating with, the soil they’re growing in, weather conditions, or other aspects of their growing environment.

We once cooked a small batch whose flavor ended up being too peppery to finish.

However, most indigo milk caps we’ve found meet the following flavor description: mild, sweet and nutty with a hint of cracked pepper on the finish.

Do indigo milk cap mushrooms stay blue when they’re cooked?

Unfortunately, indigo milk cap mushrooms do not retain their bright blue color after cooking (they will retain more blue color when frying, since that’s a much faster process). The longer indigo milk cap mushrooms cook, the more they take on a grey color.

We’ve read that there are methods for pickling indigo milk cap mushrooms wherein the high acid environment prevents oxidation thereby allowing them to retain their blue color, but we’ve yet to try this approach. 

Indigo milk cap mushroom recipe

Indigo milk cap mushrooms breaded and ready to fry!

Our favorite way to cook and eat indigo milk cap mushrooms is to fry them and dip them in homemade barbecue sauce made from home-grown tomatoes. 

Here’s our indigo milk cap mushroom recipe in case any of you other mushroom enthusiasts out there are searching for a recipe to try with your indigos:

Print

Fried indigo milk cap mushrooms (Lactarius indigo)

Course: Appetizer, brunch, Dinner, lunch

Cuisine: American

Keyword: indigo milk cap mushroom recipe, indigo milk cap mushrooms, indigo milk cap recipe, Lactarius indigo

Prep Time: 30 minutes

Cook Time: 15 minutes

Total Time: 45 minutes

Servings: 3

A simple and delicious fried mushroom recipe featuring indigo milk cap mushrooms (Lactarius indigo).

Ingredients

• 1 cup flour organic all purpose for frying mix + 1/2 cup for "dredging" your mushrooms (explained in instructions)
• 1/2 teaspoon baking powder
• 1/2 teaspoon fine ground sea salt
• 1/2 teaspoon smoked paprika + 1/2 teaspoon regular paprika
• 1/2 teaspoon onion powder
• 1 teaspoon garlic powder
• dash of chili powder
• dash of fresh ground black pepper
• 1/8 teaspoon mustard powder
• 1 large egg we use duck eggs
• 1/3 cup whole organic milk we use organic whole or raw milk
• enough organic sunflower oil or other frying oil to cover your mushrooms in whatever pan you're using we use a flat-bottomed wok
• 5 large Lactarius indigo mushroom caps or 10 small caps

Instructions

1. Chop mushrooms into the desirable sized chunks. We quarter or half them.
2. Put 1/2 cup of flour in a medium sized bowl. This is your "dredging" bowl. You'll want to get a light dusting of flower on the entire outer surface of each mushroom before you dip in the milk/egg mixture.
3. Add your egg and milk into another mixing bowl, and whisk together. You'll dip your dredged mushrooms into your egg/milk mixture before placing them in your frying mix.
4. Prepare your frying mix by putting all dry ingredients (flour, spices, etc) into a large bowl. Whisk them together until evenly blended. Once your mushrooms have been: 1) dredged, and 2) dipped in your egg/milk mixture, you'll drop them into the big bowl of dry ingredients and cover them evenly.
5. Once uniformly covered with fry mix, shake off any extra fry mix. We like to place them on a drying rack on top of a cookie sheet until we're ready to put them in the fryer (you can just use a plate if you'd prefer).
6. Heat your cooking oil. Our stove top doesn't cook particularly hot or cold, so we put it on about 4.5. You'll know your oil is hot enough when you drop a bit of flour in and it starts sizzling.
7. Go ahead and get a drying/cooling sheet ready before you start frying your mushrooms. We like to use a cookie sheet with a drying rack on top. On top of the drying rack, we put down paper towels to soak up any extra oil.
8. Next start frying your mushrooms to golden-brown and crispy perfection. It should only take about 4-5 minutes to cook each mushroom if the oil is in the ideal temperature range.

9. Remove from oil with strainer and let dry and cool on drying rack. Serve as-is or with a homemade heirloom tomato bbq sauce (our preference).

10. *Do note that indigo milk cap mushrooms do not retain their bright blue color after cooking. The longer they cook, the more they take on a grey color.

Indigo milk caps fried and ready to dip into some homemade heirloom tomato-based bbq sauce. Yum!

Serve and enjoy!

Note: As mentioned above, Lactarius indigos will lose at least some of their blue color when cooked, turning grayish-blue. When fried, they’re wonderful served straight or with a bit of sauce (we dipped some in a homemade tomato-based bbq sauce).