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Interview with Experienced Dutch Mushroom Grower and Researcher Jop Mens

I’m pleased to present a special post this week featuring an interview with Dutch mushroom grower and researcher, Jop Mens.

I’m pleased to present a special post this week featuring an interview of a new friend I’ve made in the amateur mushroom growing community: Jop Mens.

Jop is a vocal and respected voice in the world of mushroom growing and dedicates much of his time towards helping to educate newcomers to the expansive fields of diy biology, mycology, botany and more.

I think you’ll enjoy learning more about Jop, his background and his general perspective. Enjoy!


How did you get started with growing mushrooms?

When I was studying chemistry and some philosophy in college I grew magic mushrooms (psychedelics), starting out with a kit. It was still legal here at the time, before the government banned those kinds of mushrooms in response to incidents with tourists.

I got some results with the kit but unfortunately it contaminated prematurely. After that I grew more of them with my own materials, using a classic method (PF tek). And some “monotubs” as well. At the time I did not focus on fungi much, the real passion came later.

I’ve always loved DIY with many things, but particularly fermentation. I brewed cider when I was in high school.

The sheer make-ability of all that, it is like sorcery to me. Chemistry also fascinates me because there is both an inquiry into what the world is made of fundamentally as well as an exploration of what is possible and what can be created or transformed.

How did your interest in growing develop over time?

I went through a hard time after college and having a job in IT for a while, I had to move around a couple of times. I live in the south of the Netherlands again now. When I got an apartment and could stop moving, I built a cabinet for growing plants. 

Jop’s Plant & Cacti Grow Cabinet

Basically “I came for the mescaline containing cacti (and other ethnobotanicals) and stayed for the beauty”. Those were never for consumption anyway, but actually most I have now are sister species and varieties and virtually contain no mescaline at all.

Then the same sort of thing happened with growing mushrooms. I started trying to grow gourmet edible mushrooms and soon enough looked into other applications and other species and it really took off.
My penchant for experimenting and a tendency towards novelty became evident in my projects and I also started to collect different species like a madman. There are dozens upon dozens and they were basically all traded from all over the world.

I was helped poorly in my search for work and basically wasted a year of my life checking out 2 traineeships, just waiting on bureaucracy until neither worked out. This made me frustrated and angry, but that anger gave me a drive to make my own destiny.

And then in one moment I realized how starting my own business focused on novel applications of fungi could combine my interest in nature, my aptitude for science and experimentation (and background in chemistry), my budding passion for fungi, all into one.

I know Holland has one of the more liberal drug policies that attracts people from all over the world, with psychedelic sclerotia legally sold in “smart shops”. How do you think that impacts the amateur mushroom community?

Despite being legal, mushrooms then and sclerotia now may still be misunderstood and feared, just as psychedelics in general. This has started to shift significantly only since relatively recently. The US, Paraguay and Portugal for example have all surpassed the Netherlands with laws for cannabis, which is not legal here but only condoned in an inelegant and sometimes messy way.

Psilocybin-containing sclerotia are often called magic truffles, which is technically incorrect. Actual truffles are underground reproductive fruiting bodies and they spread spores which are similar to seeds. It’s fascinating really: they have evolved to become so aromatic to attract certain kinds of critters even from underground, so that they would get covered in spore mass and take it away with them to spread it around.

However sclerotia are differentiated hardened tissues which act more like the tubers of plants (such as a potato). They are not just a storage vehicle for nutrients but also protect the fungus from the elements until conditions become suitable once again.

The amateur mushroom community which revolves for a significant part around psychedelic mushrooms remains mostly underground (just as growlights immediately make people think about growing cannabis, and if I mention growing mushrooms a lot of people also assume psychedelic ones).

To be fair, it is how I started originally of course!

My country had progressive ideas at one time, but managed the issue of drugs terribly so now there is a lot of organized crime and the European Union also made it very hard for the Netherlands to really manifest those liberal ideas about drugs.

It must be a big difference though, for there to not be a ‘war on drugs’ in this country. You are generally left alone as a user and judged by the actual problems that may arise and not on principle.

As far as I know the mushroom community was never a very well represented and outspoken one, probably because in absolute terms mycology (the study of fungi) is very lol populated but in relative terms it seems those growing psychedelic mushrooms are overrepresented among amateur mushroom growers. I think it is because psychedelic mushrooms are illegal so they force more people into growing their own and a part of them discover how much they like the growing in general. It wouldn’t happen that way with gourmet mushrooms.

Wild Clone of a Stinkhorn Mushroom Egg (Phallus impudicus)

There are apparently very few people working on fungi as I have learned becoming introduced to the world of mycologists. (I go on excursions with a group of – mostly elderly – mushroom enthusiasts with a quite different angle at them).

Most of them just love the fungi and are not that distracted nor attracted by issues of legality or applications even as food. This really surprised me, enjoying eating wild mushrooms just seemed like a very convenient byproduct of hunting them but it seemed like it didn’t enter their minds for the most part.

What do you do professionally now, and what will you be doing in the future?

I have an agreement with a world renowned art academy (it is not really a school, but basically hosts post-doc level artists for a year long residency) to grow fungi for them. A grow room (dubbed the Mush Room) was already designed and built by me. But due to covid I cannot continue my project there until september and I am using the time to finish building other facilities elsewhere.

Their restaurant is one of the “labs” there and it is integrated in a bio & eco focused mother department. I will produce mushrooms for a large part but can also experiment with growing more unusual or difficult species for eating as well as fungi to use for bio-materials and bio-art. The methods will be taught to other staff members to free up time for me to develop more projects methods and experiments, repeat.

I also sell and trade cultures of fungi but not yet in a professional capacity, as I cannot and will not prioritize it over work for the academy.

Other than that I am working on multiple new concepts for utilizing fungi in novel ways, and I study/explore crossing and hybridizing them.

“Learning to grow is much less bewildering if you try to enjoy the process…”

Jop Mens

What are some misconceptions about growing mushrooms?

There are a number of myths, for example that mushrooms require darkness to grow yet paradoxically when lighting is used people may forget that they are not plants that perform photosynthesis so it does not have to be intense light (preferably not overly bright actually).

But also among growers certain myths can become very persistent because it is kind of an obscure and closed off world and much work still needs to be done. There isn’t quite as much work being done on fungi as we might like and we have barely gotten started from a historical perspective, shockingly.

And so it seems that many of us have an inborn fear and distrust of fungi which are ours to shake, for our benefit at least. As with many primordial instincts, purely from an evolutionary survival point of view it pays to be apprehensive, but in many subtle ways we hold ourselves back if we cannot dispel the irrational parts.

Mycophobia (the fear of fungi) may originate from our associations with disease, death and decay whether it is our bodies or plants/trees or our food that may become infected… it is not the whole picture. If that is where we stop to think about it, I feel we are hung up on our egocentricity, how it affects us personally.

The other part of the story is that fungi can complete the picture of recycling. Hardly never do we appreciate that earth would be uninhabitable if dead materials would just pile up instead of returning them to nature for new life to flourish.

If there was one thing you wish you knew when you started learning mycology, what is it?

Hericium coralloides “Coral Tooth” fungus

There isn’t one very best way to do things, not necessarily. Choices depend on someone’s own unique situation, even if we try to standardize as much as possible. Sometimes this is forgotten and someone’s success or failure is assumed to be universal for the method. Yes, at first it is good to just read a lot, assimilate and take teks (written out methods) at face value, but soon enough it becomes valuable to look into why certain steps are performed and what function they fulfill.

Understanding why different methods share things in common even if that is not immediately clear, helps to figure out what is better or worse for your particular situation and how to integrate these things into your own style.

What’s your favorite part of mushroom growing?

Haha the pinning (baby mushrooms) and fruiting of course, but also trying new things. Even thinking about them / coming up with them, as I am a sucker for novelty.

Who do you think should grow mushrooms and why?

Anyone who is interested in one or more of the following: self-sufficiency, meat substitutes, creating/growing in general, experimenting, recycling, nature/biology. And mushrooms probably.

What are you learning about mycology or planning to learn in the future?

One thing I have been working on and will keep doing is to experiment with substrates (materials to grow on as food for the mushrooms) and to learn how this connects with what different species are used to growing on in nature.

Furthermore I am learning about reproduction and how this applies to crossing or hybridizing fungi in order to make my own variety or hybrid. This also involves breeding which I like to learn about. However, there is a difference in making such a new combination, and stabilizing or optimizing it for cultivation. It seems relatively doable to make something new (although for now I am struggling a bit), and surprisingly much work to optimize afterwards.

Also some more about taxonomy (classifications of species and other such categories), however I am beginning to learn just how much confusion there is even among experts, and it also makes me doubt the importance of fixating too much anyway on whether 2 fungi are the same species or not. It is a matter of perspective and focus of what is different versus what is shared in common.

There is a lot to be done in new applications, including bio-materials, bio-art and new foods and I have barely touched yet on this but I can already see the avenues.

What is the biggest challenge for new growers and what can newcomers do to overcome those challenges?

I can discuss some practical matters like learning how to do sterile procedure if you have never done this before, and how it could be frustrating especially if you hardly have the right tools invested in, or expect too much too fast…

But in my opinion the real challenge is one of attitude. It can be very hard if you are focused on results and look at everything as a means to complete a goal just beyond the horizon. While it is good to have direction, learning to grow is much less bewildering if you try to enjoy the process and accept that depending on your goals you have to invest a certain amount of time and dedication and most of all: faith and patience.

Occasionally fungi appreciate neglect, but overall it will work best if you like to learn to grow and are not just interested in getting the mushrooms as soon as possible.

How would you recommend someone who is starting from scratch get started?

Some are apprehensive about investing and like to get a kit of some oysters on coffee grounds, or do a little more yourself like injecting liquid culture of fungi from a syringe into bags of substrate bought pre-made. Which might help to inspire but tends to be relatively costly and I don’t think it is representative of doing your own growing and more symbolic.

Beyond that a real pressure cooker (for canning, reaching at least 15 PSI) tends to be essential although there are ways to go even without one. I have never done this myself but brown rice is said to be one of the least naturally contaminated grains and can be sterilized fine in lesser pans.

Doing agar in petri dishes or makeshift dishes is also part of solid basics for growing, for this it is also possible to be frugal before getting professional gear (if you do at all).

Not doing your own agar, you could buy liquid cultures of gourmet mushrooms and use this to inoculate brown rice as your spawn (“seeding material”), which you could expand to substrate from just hardwood fuel pellets you quick pasteurize with poured boiling water in filterbags.

It is not something I’ve done in particular but it’s what I come up with stringing together some really low threshold methods.

What, if any, economic opportunities are there for mushroom growers?

I am not one to ask. Still finding my own way exploring different business models but preferably niche ones, and the project at the academy is a pretty unique one. I also don’t plan to become a large scale producer who just competes with other producers, that is not my strong suit and it is not interesting to me.

As far as I know mushroom growing is on a rise though, and there are holes in the market – the white button industry is quite big but they are grown differently than woodlovers.

A market also needs to be created a bit, people don’t seem to be quite so used to oysters and shiitake yet at least not in all regions.

Other than mushroom growing, what other diybio or amateur science projects are you interested in?


I’m interested in plant tissue culture which I experiment with but I have only had limited success so far, I find it quite challenging and it can be more work than mushroom lab work. The goal I have for it is to be able to acquire small tissue samples of rare cactus genetics and culture them to get new plantlets. For example one professional Ariocarpus grower/breeder said he was interested in it and would send me tissue samples for free if I would keep him posted. I’ve ordered some seeds but have not yet gotten tissue yet, but I also haven’t pursued or reminded him.

I’ve also investigated bio-materials a bit and it is something i want to continue once the show is on the road at the academy. I made a prototype wallet out of SCOBY leather, so made from bacterial cellulose out of kombucha. I still want to isolate the bacteria responsible for it out of kombucha but all of this got on the back burner.

How can folks stay connected with you and everything you are working on?

Right now anyone can just e-mail me at [email protected] on Instagram @mycomatters.

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