Grow guide
How to fruit an oyster mushroom grow kit
By Shroom Labs. Published .
Cut the bag open on a fully white kit, keep the cut face damp but never dripping, give it plenty of fresh air and about 12 hours a day of low light, and keep it cool. Pins show in about 4 to 5 days and the first harvest is done about 13 to 15 days after you open it. Our pearl oyster profile pins at 18 °C (64 °F) and 93% humidity, then fruits at 16 °C (61 °F) and 88%. Blue oyster runs a few degrees cooler, at 15 °C (59 °F) to pin and 14 °C (57 °F) to fruit.
What an oyster kit needs to fruit
An oyster kit is a block of substrate that the mycelium has already grown through. The hard part is done when it arrives. Your job is to change four things so the block switches from growing mycelium to growing mushrooms: cooler air, damp air at the cut, fresh air, and light.
These are the settings in our free pearl oyster and blue oyster grow profiles. Pinning is when the tiny first mushrooms form. Fruiting is when they grow to picking size.
| Setting | Pearl oyster | Blue oyster |
|---|---|---|
| Pinning stage | 5 days | 4 days |
| Pinning temperature | 18 °C (64 °F) | 15 °C (59 °F) |
| Pinning humidity | 93% | 94% |
| Fruiting stage | 10 days | 9 days |
| Fruiting temperature | 16 °C (61 °F) | 14 °C (57 °F) |
| Fruiting humidity | 88% | 87% |
| Light, both stages | 12 h a day, about 90 lux, blue | 12 h a day, about 90 lux, blue |
| Chamber fan while fruiting | 40 s every 10 min | 40 s every 10 min |
Pinning plus fruiting is 15 days for pearl and 13 days for blue. That is the count from a fully colonized kit to the end of the first harvest. Grower guides land in the same place: a USDA SARE funded oyster booklet puts the harvest about 5 to 10 days after a block goes into fruiting conditions (Crosby 2016).
Day by day steps for an oyster kit
- Day 0, check the block. It should be white and firm all the way through. Brown patches mean it is still colonizing, so keep it closed and warm for a few more days. Our profiles colonize at 24 °C (75 °F) for pearl and 22 °C (72 °F) for blue.
- Day 0, cut it open. Cut where the instructions that came with the kit say, usually an X or a slit in the side of the bag. Pins form where the block meets air, so that cut is where your mushrooms will grow.
- Day 0, move it somewhere cool and bright. Pick a spot around 15 to 18 °C (59 to 64 °F) with indirect daylight or room light, out of direct sun and away from heater vents.
- Days 1 to 5 (blue 1 to 4), keep the cut damp. Mist the cut face and the air around it once or twice a day, more in a dry heated room. Never let water pool on the block.
- Days 1 to 5 (blue 1 to 4), give it fresh air and light. Fresh air several times a day and about 12 hours of light a day tell the block it has reached open air. Pins usually show by day 4 or 5. Once they do, drop the room a couple of degrees if you can: 16 °C (61 °F) for pearl and 14 °C (57 °F) for blue.
- Days 6 to 15 (blue 5 to 13), let the clusters grow. Keep the air damp and give even more fresh air than before. Mist the air near the clusters, not the caps.
- By day 15 (blue day 13), harvest. Pick the whole cluster as the caps flatten out, before the edges flip up. Twist it off or cut it at the base.
- After the harvest, rest and repeat. Let the block rest, then set it up the same way for a second flush.
Plug your open date into the grow timeline calculator to get calendar dates for each stage.
Where to cut an oyster kit
Follow the kit's own instructions first, since some are built to fruit from a pre cut window or from the top. If there are none, one X or slit on the side facing the room works. Pins sometimes form inside the bag before you open it. If that happens, cut the bag right at that spot so they can reach air.
Should you mist an oyster kit?
Yes, but lightly, and the goal is damp air more than a wet block. A University of California grower guide runs oyster pinning at 95% humidity and mists once or twice a day until the mushrooms are 30 to 40% of harvest size. During cropping it runs 85 to 92% humidity and keeps misting to stop caps cracking (UC ANR).
Do not spray the caps hard. The SARE booklet warns that mushrooms soak up water they touch and turn soggy when sprayed over and over (Crosby 2016). Penn State lists a wet mushroom surface as one of the things that makes bacterial blotch worse (Royse, Penn State).
In a dry house, a loose plastic tent with a few holes over the kit holds humidity between mistings. Leave it loose so air still gets in.
How much fresh air does an oyster kit need?
A lot. The SARE booklet puts it simply: with oysters, the more fresh air the better. Mushrooms breathe out carbon dioxide, and too much of it gives long stems and small caps.
- UC ANR runs 4 fresh air changes an hour at pinning and 4 to 6 while cropping, with carbon dioxide under 600 ppm (UC ANR).
- Penn State brings in enough fresh air at pinning to drop carbon dioxide below 700 ppm (Royse, Penn State).
- The SARE booklet aims for under 800 ppm and says fruiting can stall above 1200 ppm (Crosby 2016).
A kit on an open counter usually gets enough. A kit in a closed cupboard, a sealed bag or a small box does not. Our profiles step the fan up from pinning to fruiting for the same reason. If you grow in a box or chamber, check it with the fresh air planner, and see long stems and small caps if the clusters stretch.
How much light does an oyster kit need?
Not much. Penn State gives oysters 50 to 300 lux of cool white light after the spawn run (Royse, Penn State), and UC ANR says diffuse natural light is enough (UC ANR). Our profiles run 12 hours a day at about 90 lux with a blue bias, because oysters start fruiting under blue light and barely respond to red (Richartz and MacLellan 1987). Room light or a window with no direct sun does the job. Do mushrooms need light? has the full numbers.
What temperature should an oyster kit fruit at?
Cool room temperature. UC ANR pins oysters at 55 to 60 °F (13 to 16 °C) and crops them at 60 to 64 °F (16 to 18 °C) (UC ANR). The SARE booklet says most oysters fruit best in the mid 60s °F and keeps them between 55 and 70 °F (13 to 21 °C) (Crosby 2016). Penn State lists fruiting below 10 °C (50 °F) among the causes of deformed oysters (Royse, Penn State).
Blue oyster is the one to keep cool. In a warm room the blue fades toward grey and the stems get longer, which is why its profile fruits at 14 °C (57 °F). Pearl oyster is more forgiving and fruits at 16 °C (61 °F) in its profile.
When to harvest oyster mushrooms
Pick the whole cluster at once, when the caps are flattening out and the edges still have a slight roll. UC ANR harvests just before the curled cap edge turns flat (UC ANR). The SARE booklet says to pick before the edges flatten completely or flip up, which keeps the texture and cuts down on spores (Crosby 2016).
Do not wait long. Oysters grow fast, and the SARE booklet notes that in the 60s °F growers often pick twice a day. Mature oysters drop a lot of spores, and Penn State notes that inhaled spores can cause an allergic reaction in some people (Royse, Penn State). Another reason to pick on time and keep the kit somewhere with good airflow.
Store the harvest in the fridge in a paper bag or a container with holes. The SARE booklet keeps oysters at 36 to 38 °F (2 to 3 °C) for about 10 days, and says they rot in 1 to 2 days in a sealed container (Crosby 2016).
How to get a second flush
After the first harvest, pull off any stem bits left in the cut and let the block rest. UC ANR spaces oyster flushes about 10 days apart (UC ANR). A block that feels light and dry often pins again after a few hours soaking in cold water. Then set it up the same way as the first time. Each flush is usually smaller than the last.
If your oyster kit is not fruiting
Give it two weeks from the day you open it. If nothing has happened by then, the cause is almost always one of the same few things: the block was not fully colonized, the room is too warm, the cut dried out, there is too little fresh air, or it sits in a dark cupboard. Mushroom grow kit not growing walks through them in order, and why your mushrooms are not pinning covers fruiting triggers in more depth.
FAQ
How long does an oyster mushroom kit take to grow?
About two weeks from opening a fully colonized kit. Our profiles give 15 days for pearl oyster and 13 days for blue oyster from the first day of pinning to the end of the first harvest, with pins in 4 to 5 days.
Should I mist my oyster mushroom kit?
Yes, lightly. Mist the cut face and the air around it once or twice a day, more in a dry room, and never so much that water pools or runs off the caps.
Why are my oyster mushrooms all stem and no cap?
Too little fresh air. Carbon dioxide builds up around the kit and the stems stretch looking for open air. Move the kit out of any cupboard or sealed bag and give it more air.
Why did my blue oysters turn grey?
They were fruiting too warm. Blue oysters hold their color best below about 18 °C (64 °F), and our blue oyster profile fruits at 14 °C (57 °F).
When should I pick oyster mushrooms?
When the caps have mostly flattened but the edges still curl under a little. Pick the whole cluster at once, before the edges flip up.
Sources
- UC ANR, Cultivating Mushrooms on Small Family Farms, oyster spawn run, pinning and cropping parameters
- Royse, Cultivation of Oyster Mushrooms, Penn State College of Agricultural Sciences
- Crosby 2016, Growing Oyster Mushrooms, USDA SARE funded grower booklet
- Richartz and MacLellan 1987, Action spectra for hyphal aggregation in Pleurotus ostreatus, Photochemistry and Photobiology 45
- Our pearl oyster and blue oyster grow profiles, for every stage length, temperature, humidity, light and fan setting above
Grow guides for the species in this post
- How to grow Pearl Oyster (Pleurotus ostreatus)
- How to grow Blue Oyster (Pleurotus ostreatus var. columbinus)
Keep reading
- Mushroom grow kit not growing
- Do mushrooms need light?
- Grow timeline calculator
- Fresh air and humidity planner
- Why your mushrooms are not pinning