My grow kit is doing nothing: seven reasons, and what to do in each case

There is a block in the utility room, you mist faithfully, and nothing happens. No pinheads, no fuzz, no movement. The question whether the block is dead lands in our inbox daily, and the answer is nearly always the same: no, it is waiting for something. Below are the seven causes we see most often when a grow kit stalls, in order of likelihood. Work through them top to bottom.

1. The block is too dry

The most common cause, by a distance. A grow block should feel moist at the cut, and the air around it needs to be humid too. Mist once a day in a heated room and that moisture is gone within an hour, leaving the block waiting for the other 23. Fix: mist two to three times a day, including the plastic around the opening, and move the block away from the radiator. A shallow tray of water next to the block, or an upturned clear box with a few air holes placed loosely over it, creates a microclimate in which things usually get going within a week.

2. The block is too warm

Oyster mushrooms prefer to fruit between 12 and 20 degrees. A living room at 22 degrees with the heating on is already above that, and a block on top of the fridge or next to a heating pipe gets warmer still. Warmth keeps the mycelium in growth mode instead of fruiting mode. Fix: move it to the coolest room in the house, the hallway, the garage or an unheated bedroom. One exception: the pink oyster actually wants warmth, so that one stays indoors.

3. There is too little fresh air

A block in a closed cupboard, a sealed box or a shut cellar gets too much of its own exhaled CO2. The mycelium reads that as "I am still deep inside the wood" and makes no mushrooms, or only long stems with tiny caps. Fix: a spot where a door or window opens now and then. No draught on the block itself, but moving air in the room.

4. It is too dark

Mushrooms do not need sunlight, but they do need light to know which way is "out". In a dark cupboard they wait for a signal that never comes. Fix: daylight in the room, without direct sun on the block. Anywhere you could read a book without a lamp is enough.

5. The block is still recovering from the journey

A freshly delivered grow block has spent a day or two in a box, been jostled and gone through temperature swings. The mycelium recovers from that, which takes a few days to a week. Fix: patience, and in the meantime simply follow the instructions. Silence in the first week after arrival is no problem, silence in the third week is.

6. The block is in its rest period

If you have already harvested once, silence afterwards is normal. Between two flushes there are two to four weeks in which the block rebuilds its reserves. Fix: keep misting and wait. To nudge the second flush along, submerge the whole block in cold water for twelve hours, let it drain and put it back. That cold shower mimics a rainstorm and is the best wake-up call we know.

7. The block is spent

An XL block of just over three kilos is good for two to four flushes, each a little smaller than the last. If the block is light, tough and bone dry inside, and you have harvested three or four times, it has simply given what it had. Fix: crumble it into the garden or over a layer of wood chips in a border. Autumn often brings a surprise from it, and if not, it is excellent soil improver.

When is a block really dead?

Rarely. A block that smells sour or rotten, is slimy inside, or turns green or black over large areas is lost. Everything in between, from bone dry to musty, can be revived with water, coolness and air. Unsure? Send a photo and your order number via the contact page. When in doubt we would rather take a look once too often than see a good block end up in the bin.