If you’re searching for mushroom grow bag yield or oyster mushroom yield per bag, you're probably trying to figure out how much harvest to expect from a single bag of substrate.
Let’s break it down — in simple, practical terms.
In mushroom farming, yield usually means the weight of mushrooms harvested from one grow bag, compared to the weight of the substrate inside the bag.
Sometimes it's measured in percentages. Sometimes — in pounds or kilos. Both are helpful.
Let’s say you have a standard grow bag that weighs 10 kg (22 pounds). In most cases, you’ll harvest around 2.5 kg (5.5 pounds) of oyster mushrooms from it — after two flushes. That’s about 25% of the total weight.
This 25% number is what most growers refer to when they say “yield”.
So if your bag weighs 20 lbs, a harvest of 5 lbs of mushrooms is totally normal.
Of course, it depends on your substrate quality, spawn rate, and grow room conditions. But if your setup is good, that’s the average to expect.
You might find some sources saying you can get “100% yield”. That’s not wrong — they’re just using a different method.
They mean 100% of the dry matter.
Here’s how that works:
Still, most growers talk about yield as a percent of total bag weight — not dry matter. That’s easier to track.
📌Watch my video "Yield per block"
Most of the harvest — about 60–70% — comes in the first flush. The second flush gives you another 30–40%.
After that, yield drops off. Many commercial farms don’t bother with a third flush — it takes time, space, and microclimate control, but gives little back.
One grow bag (about 10–11 kg/24 lb) usually needs 300–350 g (0,7 lb ~= 10 oz) of grain spawn.
That means 1 kg of spawn (2.2 lb) can inoculate around 3 grow bags, and if your conditions are good, you’ll harvest 6–7 kg (13-15 lb) of mushrooms per kilo of spawn (total of two flushes).
If all the conditions of the microclimate are maintained, you can expect to get 17-20% of the weight of the block from the first flush. This equals 1.9-2.2 kg (4.2-4.8 lb) of mushrooms per bag.
If the bags are placed in a damp basement with minimal ventilation, at temperatures between 11°C (52°F) and 18°C (64°F), you can expect to harvest between 1.3 and 1.8 kg (2.9-4 lb) per bag.
Not really. More spawn means faster colonization — but not necessarily more mushrooms, especially if your substrate is already nutritious.
The only time extra spawn can help with yield is when you’re using poor-quality substrate — like straw from drought years. Then the spawn can “add” some nutrition and slightly boost the harvest.
I explain this in more detail in one of my videos — link below.
There are two main ways to boost your oyster mushroom yield:
You can improve the nutritional value of your substrate mix by adding plant-based materials high in nitrogen — such as legume straw or hay, soybean straw or hulls, or sugar beet pulp.
Which supplements are best for you depends on your substrate preparation method.
📌More details here.
If you're lucky to have access to cotton by-products in your region, your yields can be especially high.
For example, many mushroom growers in Turkey harvest 27–30% of the substrate weight in a single flush and then discard the blocks.
Preventing your blocks from drying out, becoming oversaturated, or collecting condensation is key. These issues often lead to the death of primordia, pins, or young mushrooms — all of which reduce your total yield.
It happens: some holes produce mushrooms, others don’t. That’s usually a sign your microclimate needs adjusting — maybe there's too much moisture, not enough airflow, or temperature stress.
A quick trick: when you see primordia forming, put a sticky note near the empty holes. Check them in 2–3 days. If nothing grows, those spots may have failed due to poor colonization or aborted pins.
If many holes remain empty, this could significantly reduce your yield.
Keep an eye on these holes during the second flush—if large, beautiful, and heavy oyster clusters develop there, that's a good sign. If the holes are still empty, you’ll need to investigate the cause.
📌For more information, read about the optimal growing room conditions.
If you're thinking about scaling up, you’ll want to know how much yield you can get per square meter of grow space.
With yields of 14–25% and good rack systems, you can expect about:
I’ve created a complete table with calculations for grow rooms ranging from 20 to 50 square meters (215 to 540 square feet).
It shows:
That table helps plan the budget and estimate profitability.
📌Read this article on my website: Oyster Mushroom Yield Per Square Meter or Per 10 Square Feet
Soaking dry, spent substrate will not revive mycelium fruiting. If the mushroom blocks are dense and heavy, you may still be able to harvest a small crop of oyster mushrooms. How?
📌Read the article What to do with waste bags.
Video: Does yield depend on the amount of spawn? How much spawn is added to the oyster mushroom substrate?
