Frequently Asked Questions

This depends on the temperature and humidity conditions. Usually between 4 and 8 weeks. After that you will get one or two more batch(es) every two weeks. 
It depends on the humidity in and around the Growkit. On average the Growkit will yield 2 to 3 batches of mushrooms, totalling around 500 grams. After every harvest you should add water to the Growkit. If the substrate shrank, refill it with new coffee grounds.
The spawnbag will survive several weeks in the fridge if you cannot start your growing experiment straight away. Some frost should not kill oyster mushroom mycelium but it is not advised to place the spawnbag in the freezer.
Mix the spawn bag with one to three full filters of fresh coffee grounds. The coffee grounds should not have waited for more than a few hours before being used.
Whenever the last coffee filter looks covered with white fluffy mycelium, you can add new coffee, usually every 2 to 5 days. Do not press the coffee grounds into the box. Do not add more than one filter at a time. Be sure that the coffee grounds are still fresh (less than 12 hours). 
Yes. Coffee filters are made from wood fibers and the mushroom loves that.

Keep adding coffee until the Growkit is filled to the edge. 
You can add used tea bags, but tea leaves do not contain as much nutrients as coffee. If you sterilize (boil or heat until 70°C) it, you can add cardboard, paper, sawdust, wood chips, straw or other wood-like material.
The growth of the oyster mushroom is made of two distinct phases

Growing phase

When you are adding coffee to the Growkit the mycelium grows and spreads. The ideal temperature for the Grey Oyster is at 24°C. Room temperature is just fine. In this phase the mushroom does not require light.

Fruiting Phase

When the Growkit is full, you wait for mushrooms to fruit. The optimal temperature at this point is 15-20°C. If you do not have a cool place at home, you can trigger the fruiting phase by putting the Growkit in the fridge for 1 or 2 days. In this phase your mushrooms need a bit of light and humidity. Spray them with water if needed. Oyster mushrooms can fruit at temperatures as low as 5°C, they will develop a dark grey color.

Around two weeks after you have stopped adding coffee, the mushrooms will start to grow and push through the tape. Move the tape aside. You can leave holes covered with tape where no mushrooms are growing.

When one mushroom of a cluster has a horizontal top or gets a sharp edge, you should harvest the whole cluster. If the mushrooms start to dry out, you can also harvest. If they dry out, mushrooms stop growing.

After you had 2 or 3 batches of fresh oyster mushrooms, your kit will not produce mushrooms. Take the whole substrate out of your Growkit and put it onto a clean plate. Select a good-looking 20% and cut it into pieces. Clean your Growkit, close the holes with breathing tape (available from your local pharmacy), then sterilize it. Put the cut substrate in the box with a bit of water. Wait for 2 days for the mycelium to start growing again. Now you can start feeding it again with coffee!

You can put the remaining 80% of the substrate in the compost or organic waste. You can even leave it in some humid corner of your garden, it might still produce some mushrooms!

If the whole substrate is too contaminated or dried out, you can order a new Starter Kit from our webshop.

This could mean the air around the Growkit is too dry. Try moving it away from any heat source or draft. Put the Growkit on a plate and spray it with water. What can also help is covering it with a transparent plastic bag with holes in it for oxygen exchange.
Everything in your Growkit that is not coffee should look white. You can observe some yellowish or reddish liquid, which are normal enzymes produced by mushroom for processing their food. But whenever you observe some green mold (more rarely orange), you are in the presence of a fungal contamination.

Contamination can happen if you do not wash your kit before starting it, if you handle it with dirty hands, if the substrate is too dry… or simply if some mold spores (they are everywhere) win the battle towards your lovely grey oysters!

If there is contamination in your Growkit, take it out with a clean spoon. Keep a daily eye inside the box and take the mold out every time it grows back. Make sure the substrate is always humid. If however the substrate turns completely green, throw everything away, clean the box with alcohol and order a new bag of spawn at our webshop.

  • If the box is not full, you have waited too long before adding more coffee grounds. Take all growing mushrooms away and add fresh coffee grounds.
  • If you had stopped filling the box, you did it too early. Take all growing mushrooms away, fill the box completely with fresh coffee grounds and be ready to take the tape off in few days.

No. The grey mushrooms we sell for indoor use and as mushroom beds are a sporeless variety. The outdoor mushroom varieties we sell do produce spores but none of them have been classified as invasive.