Top-Fruiting vs Side-Fruiting Mushrooms: Which Way Should You Grow?

Top-Fruiting vs Side-Fruiting Mushrooms: Why Some Species Grow Up and Others Grow Out

When I first started growing mushrooms, almost everything I worked with were top-fruiting species like pioppino. Because of that, I got used to thinking of mushroom blocks as something that only fruits straight up. You open the top of the bag, and the mushrooms grow vertically. It seemed simple enough.

So when I later started growing oysters and lion’s mane, I was honestly surprised by how well they fruited out of the side of the grow block. In many cases, they actually looked better and healthier compared to the top-fruiting ones. At first it felt a little counterintuitive, but over time it started to make a lot more sense.

Mushrooms Fruit Where Conditions Are Best

One of the most important things to understand is this: mushrooms don’t care about "top" or "side." They fruit wherever they find the best combination of fresh air, humidity, and space to grow.

Different species evolved to prefer different orientations in nature, and that carries over into how they behave in your grow bags and blocks. Once I started thinking about fruiting direction this way, a lot of the confusion just disappeared.

Top-Fruiting Species (Pioppino and Enoki)

Some mushrooms are naturally top-fruiting. Species like pioppino are usually grown by opening the top of the bag and letting the mushrooms grow upward. These mushrooms tend to do a few specific things:

• Form tighter clusters

• Grow tall, vertical stems

• Respond well to controlled openings at the top

This setup works great for species that evolved to push upward through leaf litter or soil-like environments.

[Insert photo: Top-fruiting pioppino growing vertically from the block]

Side-Fruiting Species (Oysters and Lion’s Mane)

Oysters and lion’s mane behave very differently. In the wild, oysters often grow horizontally from logs or tree stumps. Lion’s mane usually fruits from wounds or openings in wood rather than growing straight up. Because of that, these species often do extremely well when you give them a side cut in the grow bag.

When I first tried this, I noticed a few big improvements:

• Cleaner clusters

• Better-shaped fruits

• Less crowding

• Easier harvesting

I used to use sterile disposable scalpels to make these cuts, but they got expensive fast. I eventually learned that a simple craft knife works just as well. They are much cheaper and the blades last longer. Plus, you can buy a huge pack of replacement blades for a few dollars and they will last you for dozens of blocks.

Switching Directions Across Flushes

One interesting thing I have seen, especially with lion’s mane, is how the fruiting direction can change between flushes. Some growers like to switch things up to get the most out of their blocks. They might allow the first flush to fruit from the top, harvest it, then wrap the block tighter as it shrinks and cut an X in the side for the second flush.

This can work well because after that first harvest, the block has lost some volume. Side cuts can sometimes provide a better microclimate for the next round of growth. It isn't a hard rule, but it is a great option to have depending on your environment.

There Is No "Wrong" Fruiting Direction

This is the part I think beginners need to hear most: there isn't one "correct" way for mushrooms to fruit. If your mushrooms are growing healthy, forming well, and not drying out, then your setup is working. It doesn't matter if it doesn't match exactly what you expected at first.

Top-fruiting and side-fruiting are just tools you can use, not strict rules you have to follow.

Final Thoughts

Learning how different mushrooms prefer to fruit was one of those moments that helped everything click for me. Once I stopped trying to force them to grow a certain way and instead worked with how each species naturally behaves, my grows became more consistent and a lot less stressful.

If your mushrooms are growing well, they are telling you something is right. Sometimes all you need to do is listen.

Making the right cut is only half the battle. If you have your bag ready and want to know the exact steps to trigger those first pins, check out my full guide on how to initiate fruiting for oysters.