Light and Temperature

Mushrooms want light — but not much

Wait, don't mushrooms grow in the dark? Not quite. A fungus does not eat sunlight the way a green plant does, because it has no chlorophyll (the green stuff that turns light into food). But an oyster mushroom still uses light as a signal.

Light tells the fungus, "you have reached the open surface — time to make caps." It helps the mushrooms start pinning (forming baby mushrooms), grow their proper oyster shape, and point their caps the right way.

What they want is indirect light — soft, bright-enough-to-read-a-book light, like a shady windowsill or a room lamp.

• Good: near a window but out of the sun's direct beam, or under a normal room light.

• Avoid: direct sunlight. A sunbeam is hot and drying, and it will bake and shrivel your damp caps.

You do not need a special grow light. Ordinary daytime brightness for several hours a day is plenty.

The right temperature

Temperature is how warm or cool the air is. Every mushroom has a range it likes best, and outside that range it grows slowly or not at all.

Most oyster mushrooms fruit well at normal, comfy room temperatures — roughly 18 to 24 degrees Celsius, which is about 64 to 75 degrees Fahrenheit. A cool spot around 20 degrees Celsius (68 Fahrenheit) is a great target, and a slight dip in temperature can even help trigger the first pins.

• Too hot (near a radiator, oven, or sunny window): the block dries out, the fungus gets stressed, and caps may not form.

• Too cold (a freezing garage or fridge): growth almost stops and pauses until it warms again.

• Just right: a steady, room-temperature corner away from heaters and draughty cold.

Different oyster types like slightly different ranges, so it is worth checking the note that came with your kit. But a normal room in your home is usually close to perfect.

Putting the spot together

The best place for your kit ticks both boxes at once: gentle indirect light and a steady comfy temperature. A kitchen counter away from the stove, or a shelf near a shaded window, often works well.

Safety note: your kit is a known-safe oyster mushroom. Never pick or eat wild mushrooms — many look similar but are poisonous, and only an expert can tell them apart. Grow and cook with an adult, and always cook oyster mushrooms before eating.

Light and warmth are needs three and four. In the last lesson we bring all four together.