Is this normal? White fuzz, yellow droplets and dark patches on your grow kit

Most questions that land in our inbox start with a photo and the sentence: is this normal? Fair enough, because a living grow block does things no other product in your house does. The good news: nine times out of ten the answer is yes. Below is the complete list of what you might encounter on a grow kit, from perfectly healthy to reason to act.

White fuzz or fluffy white patches: normal

White fuzz is not a mould problem, it is the fungus you bought. Mycelium is white and fluffy, and wherever the block is damaged or cut it grows outward extra hard. A white haze on the inside of the plastic is also just mycelium climbing the bag. The whiter your block, the healthier it is. Action needed: none.

Yellow or brown droplets: normal

Clear yellow to brownish droplets on the substrate or against the plastic look alarming, but they are moisture the mycelium itself excretes, the fungus sweating, so to speak. It belongs to a block that is working hard, and you often see it just before mushrooms appear. Sometimes it hints that the block is slightly too warm, so if it sits next to a radiator, move it a little further away. Otherwise: leave them, do not wipe.

Yellow or orange crusty patches: usually normal

Older mycelium can turn yellow to orange-brown and get a bit crusty, especially in bright or draughty spots. That is skin forming, not spoilage. The difference from real trouble is in the texture: crusty and dry belongs, slimy and wet does not.

Blue-green or grass-green patches: not normal

Green is the colour to watch. A green, powdery patch is almost always Trichoderma, a mould competing with your oyster mushroom for the substrate. A small patch on the outside can be cut away with a clean knife, after which the block simply carries on, but keep an eye on it and wash your hands after touching. If it spreads fast or runs through the whole block, send us a photo with your order number.

Black wet patches and a rotting smell: not normal

A healthy block smells fresh, like forest floor or button mushrooms. If it smells sour, of alcohol or genuinely of rot, and you see wet, dark, slippery patches, bacteria have joined in. It is rare and it is not your fault: usually the block got too warm in transit or storage. Again: photo and order number to us, and we will sort it out.

Tiny pinheads appearing overnight: normal, and good news

A cluster of tiny beads or stubs, often in a corner or at the cut, are primordia: baby mushrooms. From here things move fast, oyster mushrooms roughly double daily in this phase. Keep misting and in five to seven days you will be harvesting.

Mushrooms with long stems and tiny caps: normal, but a signal

If your oyster mushrooms grow upward like asparagus wearing little hats, they are getting too little fresh air or too little light. They are perfectly edible, but for the next flush it pays to give the block a brighter, airier spot. No full sun, but daylight and a room where a door or window opens now and then.

Nothing has happened for two weeks: usually normal

A block needs time after arrival to recover from the journey and top up its moisture. Between two flushes there is easily two to four weeks of rest as well. Patience and daily misting is almost always the answer. If the silence lasts longer than a month, we are happy to take a look with you.

The rule of thumb

White, yellow and brown: let it work. Green, black or stench: take a photo and email us. Better to ask once too often than to throw away a block that had three more harvests in it. That is what we are here for.