Shrüm™ Harvest & Replenish Guide

This is our guide to harvesting and re-hydrating your Shrüm All-In-One Mushroom Grow Bag. Please note that once you’ve opened your bag, you may contaminate it, and we have no guarantees regarding second or third harvests or any continued use. Our customers have had tremendous success with multiple harvests, but we can’t control what happens when you open your bag. 

Ideally harvesting and rehydration would take place in front of a flow hood or in a still-air box, but we wanted to provide an informal guide for our customers using basic household items or things that are inexpensive/easy to purchase.

Read through all of this information before attempting to harvest.

For reusing a bag please note:

  • You will not be adding more genetics. You should’ve added a full syringe of liquid culture or spores at the beginning of the grow, but your cake will be fully colonized and you cannot add additional genetics. What your cake needs after harvesting in order to harvest again is hydration. Mushrooms are 90% water.

The key components are going to be:

  • Sterility
  • Rehydration

You will need:

  • Face mask (or avoid breathing towards the bag while harvesting)
  • Disposable gloves (or disinfecting your hands)
  • 70% isopropyl alcohol OR lysol OR hand sanitizer (for surroundings, hands, arm)
  • An unopened bottle of water OR 3% hydrogen peroxide (~4 oz is what you’ll use)
  • Scissors to open the bag
  • Tape to seal the bag back up
  • A room without fans blowing, open windows or anything that could blow contaminants into your bag while it’s open.


  • Gather all the items you need & prepare your environment.
    • Close windows, turn off fans.
  • Sanitize your space as best you can.
    • Lysol the air around you, use hand sanitizer on your hands, put on gloves or a mask. Whatever you can do to make the space clean and avoid contaminating your bag.
  • Cut the bag open as close to the top seal as possible, with scissors.
    • Sanitizing the scissors is a good idea.
  • Twist and pull your mushrooms out.
    • Go look for any tiny pieces – harvest ALL mushroom material at once, even baby mushrooms that aren’t ready to harvest. Once you hydrate the cake the mushroom material might start to rot. Grab it now!
  • Pour in your water or 3% hydrogen peroxide.
    • You can do this by sight – it’ll be anywhere from 2 to 6 ounces, but probably closer to four. Our Shrüm V3 mini grow bag won’t take too much. Our Shrüm V2 grow bag will take more. Don’t drown your cake, just pour in some water for it to soak up.
    • Use bottled water so you don’t accidentally contaminate your cake with anything that could be in tap water.
    • 3% hydrogen peroxide helps kill any bacteria that may accumulate, which is beneficial, it will generally fizz when poured in. It will not harm the mycelium, and will hydrate the cake as well.
  • Use tape (packing tape ideally) to seal the bag closed. 
  • Optional but helpful step: after 12-24 hours, you can actually open the bag again to pour any excess water out. The cake will absorb what it can, but excess water left for a while can breed bacteria. 

You should have another round of mushrooms within 1-2 weeks.

To dehydrate we recommend using an actual dehydrator or seeing if your toaster oven, oven or air fryer has a dehydrate setting.

Mushrooms should be dehydrated around 160°F, and may take a few hours. If you don’t dehydrate immediately, dry any water off and place them in a bag and refrigerate them for up to a week (but like regular mushrooms, they’ll rot after a while).

If you have problems, questions or need clarification on any of this, email us at!