How to grow button mushrooms at home

The white button is the most familiar mushroom in the world — and growing your own is deeply satisfying, as long as you get two special steps right.

Learning how to grow button mushrooms is a rewarding step up from the beginner kits, because buttons behave differently from the easy species and teach you real cultivation. The white button, along with its cousins the cremini and the portobello, is one strain called Agaricus, and unlike oysters it is a composting mushroom — it wants a rich, composted bed and a special top layer to fruit. Get the substrate and the casing layer right and cool it down at the correct moment, and you will pull firm, fresh buttons from a tray in your basement or garage. Here is the full process, step by step, and where beginners usually go wrong.

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Start with a composted substrate

The first thing to understand is that button mushrooms will not grow on the straw or coffee grounds that oysters love. They are a composting species, so they need a rich, pasteurized bed of composted manure and straw — traditionally horse or cow manure blended with straw and aged until it breaks down. This composting requirement is the single biggest difference from easier mushrooms and the reason buttons are considered intermediate. If you would rather start on something more forgiving first, our guide to the best beginner mushrooms covers the straw-and-grounds species, and you can always graduate to buttons afterward.

Add spawn and let it colonize

Once your compost is pasteurized and cooled to room temperature, mix in button mushroom grain spawn evenly throughout the bed. Then keep the tray warm, around 70 to 75 F, and dark while the white mycelium spreads through the compost — this colonization phase takes roughly two to three weeks. Keep the surface from drying out but do not soak it. During this stage the bed does not look like much, but the network growing beneath the surface is what will eventually push up your mushrooms, so patience here pays off.

Apply the casing layer

This is the step beginners skip, and it is the one buttons cannot do without. Once the compost is fully colonized, spread an inch or two of a moist, low-nutrient casing layer — usually peat moss mixed with a little lime — over the top. Unlike other mushrooms, buttons need this humid capping layer to trigger fruiting; the mycelium grows up into it and forms pins there. Keep the casing consistently moist with light misting. Without a casing layer you can have a perfectly colonized bed that simply never produces mushrooms, so do not treat it as optional. It works much like the humidity control in a fruiting chamber.

Fruit cool, then harvest

After casing, drop the temperature to around 55 to 65 F and give the bed fresh air and high humidity — the cool-down is the signal that tells the mushrooms to fruit. Within one to two weeks, tiny pins appear in the casing and swell into buttons over a few days. Harvest them by twisting gently when the caps are still closed for classic white buttons, or leave them longer for open-capped creminis and portobellos. A bed will usually give several flushes over the following weeks. Once picked, keep them fresh with our guide on storing fresh mushrooms. For the full botanical background, the Agaricus bisporus reference is a good read.

How to grow button mushrooms — FAQ

How do you grow button mushrooms at home?

On pasteurized composted manure and straw: add grain spawn, colonize warm and dark, apply a moist casing layer, then fruit cool at 55 to 65 F and harvest.

What substrate do they need?

A rich composted manure-and-straw bed — buttons are a composting species, unlike oysters that grow on straw or coffee grounds.

What is a casing layer?

A moist peat-and-lime top layer buttons need to fruit; without it a colonized bed may never produce mushrooms.

How long does it take?

About five to seven weeks from spawn to first harvest, with several flushes following.