How to Clone a Mushroom on Agar
To clone a mushroom on agar, you cut a small piece of clean inner tissue from a fresh fruit, set it in the center of a sterile agar plate inside a still air box or flow hood, then incubate it at 20 to 25 degrees C (68 to 77 F) until white mycelium runs the plate. That plate becomes a master culture, a living copy of the mushroom you liked, ready to expand into grain, liquid culture, or storage.
The first clone I ever pulled was off a firm oyster cap I did not want to lose. I flamed the blade, took a sliver from the inside of the stem, and dropped it on a plate. Three days later a little tuft of white was creeping out across the agar, and I had that strain on hand for years afterward. That is the whole appeal of cloning on agar. You keep the exact mushroom, not a random roll of the genetic dice.
Out-Grow Quick Answer
- Work clean. Clone inside a still air box or a flow hood, wipe everything with 70 percent isopropyl alcohol, and flame the blade before every cut.
- Take inner tissue only. The sterile interior of the stem or cap carries far less contamination than the surface or the gills.
- Incubate the plate at 20 to 25 degrees C (68 to 77 F) in the dark. Expect first growth in 2 to 7 days and a full plate in roughly 7 to 21 days by species.
- Watch for the first few days. Most failures show up as color or slime within 72 hours, and a clean wedge cut away from any problem can still rescue the culture.
- Store finished plates sealed and refrigerated for roughly 2 to 3 months, then subculture to a fresh plate or a slant for the long haul.
What You Need to Clone a Mushroom on Agar
A grower emailed me last spring frustrated that every clone he tried turned green. He had good agar and a sharp scalpel, but he was working on his kitchen counter with the window open. The gear was never the problem. Clean still air was. Cloning on agar does not take much equipment, but two pieces are not optional, a still air environment and a real heat source for your blade.
- A fresh, firm mushroom with no bruising, mold, or sliminess
- A still air box or a laminar flow hood for a clean work zone
- Poured, set, sterile agar plates, potato dextrose agar or light malt extract agar
- A scalpel or a thin sharp knife
- A flame source, an alcohol lamp or a lighter, to sterilize the blade
- 70 percent isopropyl alcohol for surfaces, gloves, and the mushroom exterior
- Parafilm or micropore tape to seal finished plates
Notice the alcohol is 70 percent, not 91 or 99 percent. That trips up a lot of beginners, and I will come back to why lower is actually better for killing microbes. If you would rather skip cooking your own media, pre-poured plates and ready made agar from our culture media collection get you to the same starting line without a pressure cooker session.
How to Clone a Mushroom on Agar Step by Step
The morning I taught my first hands-on session, the part everyone slowed down on was the cut. They wanted to gouge out a big chunk. A clone tissue sample only needs to be rice grain to pea sized, and going small keeps the surface contaminants out of the picture. Here is the sequence I run every time, start to finish.
Best Agar Recipe for Mushroom Cloning
Back when I was mixing my own media by the batch, I settled on two recipes and stopped fussing. Both grow a clone just fine, and the choice comes down to what is in your cupboard and how forgiving you want the media to be. Potato dextrose agar is the one I hand beginners. It is cheap, it grows almost anything, and it is hard to mess up.
| Media | Rough recipe per 1 liter water | Best for | Notes |
|---|---|---|---|
| Potato dextrose agar | 200 to 300 g peeled potato boiled and strained for broth, 10 to 20 g dextrose, 15 to 20 g agar | Beginners and most gourmet species | Forgiving and nutrient rich. My default for cloning. |
| Light malt extract agar | 10 to 20 g malt extract, 15 to 20 g agar | Simple mixing, wide use | Nothing to boil and strain. A little leaner can mean slower bacterial blooms. |
Whichever you pick, sterilize the finished media at 15 psi, which is about 121 degrees C (250 F), for 20 to 30 minutes depending on volume, then let it cool to roughly 45 to 55 degrees C before you pour plates in your clean zone. Do not chase a perfect pH. On a potato or malt base the natural range of about 5.5 to 6.5 is right where mushroom mycelium wants it.
How Long Does It Take for Mycelium to Grow on Agar
The waiting is the part that makes new growers second guess themselves. I have watched people pitch a perfectly good plate on day three because nothing had happened yet. First visible growth from a tissue clone takes a little time, and the full plate takes longer still, both driven by the species and the temperature.
Full colonization of the plate is where species really separates. Fast growers race across the agar. Slower species make you wait, and that is normal, not a failure.
Here is what the plate is actually doing across those weeks, so you know whether yours is on track.
What Temperature to Incubate Mushroom Agar Plates
The first incubator I rigged up was a cooler with a cheap heat mat, and I learned fast that warmer is not better. I pushed it once toward 30 degrees C thinking I would speed things up, and all I did was invite bacteria to the party ahead of the mycelium. The sweet spot for cloning on agar sits lower and calmer.
Keep the plates in the dark or in low light while they colonize. Agar cloning is a colonization job, not a fruiting one, so mycelium does not need light and warmth beyond the range above just raises your contamination odds. Steady beats hot every time.
How to Tell if Your Agar Plate Is Contaminated
The plate that taught me to read agar was one I almost used. It looked mostly white, but a faint pink sheen sat along one edge, easy to talk yourself past when you are excited. I cut a clean wedge far from it, moved on, and dodged a contaminated grain run. Learning to read a plate is the entire reason we clone on agar instead of straight to grain. The problems show themselves here, where you can still fix them.
| What you see | What it likely is | What to do |
|---|---|---|
| White, anchored, ropey or fuzzy growth running through the agar, no odor | Healthy mushroom mycelium | Keep going. This is what you want. |
| Green, black, or blue-green patches | Mold, often Trichoderma or Penicillium | Toss the plate. Do not try to save a molded plate near the mushroom growth. |
| Pink, orange, or yellow slime, wet shiny patches, sour smell | Bacterial contamination | Discard, or cut a clean wedge far from it to fresh agar and watch closely. |
| Grey, wispy, fast growth that rises up off the surface like a loose web | A cobweb-type mold, not mycelium | Remove it. It spreads fast and is easy to mistake for healthy growth. |
The trap is that not everything bad is colorful. Some molds and bacteria come in white too. The tell is the pattern and the smell. Real mycelium anchors into the agar and looks ropey or fuzzy but fixed in place, with no sour or musty odor. If a plate is sectoring into visibly different textures or throwing an off smell, treat it as suspect. If you want to go deeper on identification, our advanced mycology guide walks through culture work in more detail.
How to Store Mushroom Cultures on Agar
I keep a working library of hundreds of cultures, and none of them live forever on their first plate. That is the mistake I see most with storage. Growers pour a beautiful clone, refrigerate it, and reach for it a year later expecting it to jump back to life. Agar ages. Plan your storage around that.
For the long haul, agar slants kept cold at roughly 2 to 4 degrees C carry many species for months, often into the 6 to 12 month range and sometimes longer, though how long depends on the species. When you pull an older culture, test it with a fresh transfer before you build a whole grow around it. Weak or patchy regrowth on the test plate tells you the culture is tired and it is time to reclone from a fresh fruit.
All of this storage and testing work assumes cloning was the right call in the first place, and for a mushroom you already like, it usually is.
Cloning on Agar
Keeps one known genotype. You reproduce the exact mushroom you liked, tissue for tissue.
Starting From Spores
Spores recombine genetics through sexual reproduction, so offspring vary and rarely match the parent mushroom exactly.
Common Bad Advice About Cloning Mushrooms on Agar
Some of the worst cloning advice sounds reasonable until it costs you a plate. I have watched all three of these send good tissue samples straight to the trash. Here is what beginner guides get wrong and what is actually true.
Any white growth on the plate is healthy mycelium, so if it is white you are safe.
Some molds and bacteria grow white too. Judge by the pattern and the smell. Healthy mycelium anchors into the agar and looks ropey or fuzzy with no off odor. Wispy growth that rises up off the surface or a sour smell means contamination.
99 percent isopropyl alcohol sanitizes better than 70 percent because it is stronger.
70 percent isopropyl alcohol is the better surface disinfectant. The water content slows evaporation and helps it actually kill microbes rather than flashing off before it works. Reach for 70 percent for cloning.
A sealed agar plate keeps in the fridge indefinitely, so you can pour once and forget it.
Agar cultures age. Plan on roughly 2 to 3 months refrigerated for a plate, then subculture to fresh agar or a slant. For longer storage, keep slants cold and test an old culture with a fresh transfer before committing to it.
Relevant Out-Grow Supplies
You can clone with a kitchen knife and homemade media, but a few honest upgrades make it cleaner and faster. I only point you at what actually helps cloning on agar.
Our culture media collection carries pre-poured plates and ready made agar if you would rather not boil potatoes and run a pressure cooker. It is the fastest way to get sterile plates in front of you. Our agar plates and mushroom culture collection is worth a look if you want a proven clean starting culture to practice transfers on before you clone a wild find. And once your clone reads clean on the plate, our liquid culture syringes show you the format you will expand that verified culture into so you can inoculate many jars at once.
Cloning a Mushroom on Agar: The Bottom Line
Cloning on agar is not complicated once you accept where the difficulty actually lives. It is not the cut and it is not the recipe. It is keeping the work clean and reading the plate honestly in those first few days. Take a small piece of inner tissue, keep everything sterile, incubate at 20 to 25 degrees C, and let the plate show you whether the clone is clean before you ever commit it to grain. That inspection window is the whole reason agar beats going straight to grain, and it is what turns a mushroom you liked into a culture you can grow again and again. Start on a fast, forgiving species like oyster, get a few clean plates under your belt, and the rest of the culture library builds itself from there.
About the author
Mike Wiberg is the founder of Out-Grow, a mushroom cultivation supply company he has run since 2009. He developed the original all in one mushroom grow bag in 2014, a format now used across the hobby, and over more than 20 years of hands-on mycology he has grown hundreds of species and researched substrate formulations from the lab bench. He maintains one of the largest commercial culture libraries online, including a working collection of more than 300 species under a USDA permit. His cultivation work has been cited in peer reviewed research published in Frontiers in Cellular and Infection Microbiology, and he is one of only a handful of growers with a documented successful clone of Matsutake, one of the most difficult species in cultivation. He has helped growers troubleshoot cultivation problems for nearly two decades, and he writes from the lab and the grow room, not from a keyword list.