Stages of mushroom growth, with pictures: what each stage looks like and what to do next
Gourmet mushrooms grow through stages you can see in a jar or grow bag, from culture to pins and mushrooms; here's each in pictures and what to do next. It also covers how to tell each stage is done, the flushes after harvest and where a kit starts.
Derick9 min read
Each stage of mushroom growth has a look that says it's done: every kernel white for grain spawn, the whole bag white for most bulk bags, and gills showing under a still-curled cap edge for most mushrooms. A ready-to-fruit kit arrives colonized, so you start by opening it to fruit. Match your jar or bag to a photo below, then do the next step.
Our sources are Cornell Small Farms, UF/IFAS, GroCycle, Rootlab and North Spore's help center and booklet, checked 28 October 2026.
What are the stages of mushroom growth?
The stages of mushroom growth you can see are culture, grain spawn, bulk substrate, pins and mushrooms, then more flushes from the same block. What you watch in the grain spawn and bulk stages is colonization: mycelium growing through the grain or substrate until it covers all of it.
| Stage | What healthy looks like | Done when | What to do next |
|---|---|---|---|
| Culture | White growth spreading out from the wedge | Growth nears the plate's edge | Transfer to grain |
| Grain spawn | White threads spreading kernel to kernel | Every kernel is covered, uniformly white | Mix into bulk substrate |
| Bulk substrate | White patches growing out from the spawn and joining | The whole bag is white (shiitake: about 75% brown) | Open the bag to fruit |
| Pins | Tiny bumps, then matchstick pins at the cut | Pins swell into young mushrooms | Keep the air humid and fresh; mist from a distance |
| Mushrooms | Caps small and domed, still growing | Gills show, edges still curled under (oysters: as edges start to flatten) | Harvest |
| After harvest | Rests in fruiting conditions, then pins again | Nothing comes back | Compost it |
For how long each stage takes, see our mushroom grow timeline.
What does a healthy mushroom culture look like?
A healthy culture looks like clean white mycelium growing outward from the wedge (the bit of mushroom tissue or agar that started the plate); next, transfer it to grain. GroCycle expects to see mycelium "starting to grow outwards from the tissue" within 2 to 3 days of cloning (GroCycle).
Trouble is easy to spot on agar, because mycelium and contaminants "will grow separately" there, and contaminants "may start white and then change colour" (Rootlab). Spots of black or green are contamination (GroCycle). See what contamination looks like at each stage.
The plate is done before it fills: GroCycle says to use or store it "just before the mycelium reaches the edge" (GroCycle). A liquid culture in a jar or syringe does the same job, and Hypha's guide below calls it the more common start. A spore print is an earlier, advanced start.
In Hypha: add the plate as a Culture block with the Agar Plate container. When it's ready, tap Mark Ready, then Transfer to create its spawn, or Put into storage to keep it.
What does grain spawn look like as it colonizes?
Grain spawn starts as bare kernels, grows white threads between them, and is done when every kernel is covered; next, mix it into bulk substrate, the pasteurized straw or supplemented sawdust it fruits from. GroCycle's test: "When the grain is completely covered with mycelium and uniformly white, your jar is fully colonized, and your grain spawn is ready to use" (GroCycle).
Cornell says it is "very easy to get contamination on grain", so it's "not a beginner substrate" (Cornell). You can skip this stage with ready-made grain spawn, as we have for blue oyster (North Spore — affiliate link: we may earn a commission at no extra cost to you).
Partway through, you can break and shake it to spread the mycelium; GroCycle says some growers shake jars "when they are a third of the way colonized" (GroCycle).
Some species stay faint even when ready. North Spore's help center says lion's mane, pink oyster, hen and chicken of the woods "typically have a faint mycelium and look uncolonized" (North Spore help center); judge those by whether any bare kernels are left. Green, black, red or orange growth, or a slimy wet spot, is contamination (GroCycle). If the white stops moving, see slow or stalled.
In Hypha: tap Break & Shake when you shake it. When it's fully white, tap Mark Ready, then Start transfer to create the bulk block.
What does a colonizing grow bag or block look like?
A colonizing grow bag shows white patches that grow out from the spawn and join until the whole bag is white; next, move it into fruiting conditions. Cornell says the mycelium leaps off the spawn about four days after spawning to bulk and spreads until the patches fuse into one (Cornell).
Shiitake is the exception, with "two extra parts to colonization": after full colonization, Cornell says "the block becomes textured and bumpy", then turns brown, and it shouldn't leave incubation "until 75% of the block has turned brown and popcorned" (Cornell). See our shiitake guide.
Amber droplets are "mycelial exudate", which North Spore calls "natural and harmless" (North Spore help center), but "black, green, or orange patches" could be mold (North Spore help center). Not sure? See what looks like contamination but isn't.
To start fruiting, give the bag fresh air, high humidity, some light and the right temperature (GroCycle), and cut a slit or an X in it, except for shiitake (see its guide above); pins form at the holes (UF/IFAS). For its kits, North Spore says to "cut an X into the exposed plastic" and leave the flaps on to hold in moisture (North Spore help center).
In Hypha: tap Put into Fruiting Conditions and choose the fruiting zone.
What do mushroom pins look like?
Mushroom pins look like tiny bumps on the white surface, usually at the cut, and stretch into matchstick-sized baby mushrooms; next, keep the air around them humid and fresh. GroCycle describes "tiny little bumps starting to form on the surface of the mycelium" that become "tiny matchstick-like primordia or mushroom pins" (GroCycle). UF/IFAS says they "appear at the holes made in the plastic bags" (UF/IFAS).
The bumps are primordia, and the step is pinning; not every pin becomes a mushroom (GroCycle).
If pins dry out, "they'll stop growing", GroCycle says, so mist often, but "from a distance using a fine mist" so the spray doesn't damage them (GroCycle). North Spore says pins usually abort when "there isn't enough humidity around the block" (North Spore help center). Humid doesn't mean sealed: when CO2 is high, mushrooms "form with long stems and little caps" (Cornell), so give them fresh air. No pins yet? Our pinning guide covers whether the block is ready.
In Hypha: in the phone app, add a photo to the block each day, so you can see what changed since yesterday.
What do fully grown mushrooms look like?
Fully grown mushrooms show their gills while the cap edge is still curled under; after that, the caps flatten or turn up and start dropping spore dust. Cornell says to harvest most cap-and-stem mushrooms "as the gills are exposed but the cap margin is still curled under" (Cornell). UF/IFAS says oyster caps "are rolled into a convex shape when young" and "flatten out as the mushroom ages" (UF/IFAS).
For oysters, GroCycle says it's "time to harvest" once the edge of the caps "starts to flatten out or turn upwards", before they begin "dropping lots of spores" (GroCycle). Check daily: North Spore's booklet says mushrooms can pass "their peak harvest time" in a single day (North Spore booklet).
Lion's mane has no cap, so pick it before the spines turn yellow (lion's mane guide). Our oyster guide covers how to harvest.
In Hypha: tap Harvest Flush and enter the Fresh Weight.
What happens after the first harvest?
After the first harvest, rest the block a week or two in fruiting conditions and it can fruit again; when nothing comes back, it's spent. Each crop is a flush. For oyster, chestnut and pioppino bags, Cornell says "Second flushes will happen from the same cut" (Cornell), and UF/IFAS expects "2–4 more flushes" from oyster bags (UF/IFAS). Our second-flush guide covers when a block is done and what to do with it.
In Hypha: each logged flush sets the next flush reminder. When the block is done, tap Finish, choose Successful or Failed, and leave Archive block checked.
What stage is a mushroom kit at?
A mushroom kit starts at the end of the bulk stage, already colonized, so your first job is to open it and wait for pins. Our beginner kit guide walks through a kit's first two weeks. A ready-to-fruit block, such as a blue oyster fruiting block, starts at the same point (North Spore — affiliate link: we may earn a commission at no extra cost to you).
In Hypha: add the kit as a bulk block in a Bulk Bag (an All-in-One Bag adds Break & Shake reminders a kit doesn't need), and tap Put into Fruiting Conditions the day you open it.
How do you follow these stages in Hypha?
You follow these stages in Hypha, our grow tracking app, by adding each plate, jar, bag or kit as a block at its stage. Before you add your first block, tap "New to growing? See the grow stages" on the Grows tab to open Typical grow stages. Later, it's behind the ⓘ on the Growth Stage picker.
Reminders show on each block's timeline and in the Schedule tab, from default timings that are the same for every species, so adjust them for shiitake. They go by date and tell you when to look; the photos above tell you whether a stage is done.
The guide, reminders, photos and QR labels are on the free plan, which holds 25 active blocks; each counts until you archive it, so Finish used plates and jars too. Download Hypha.
FAQ
What are the stages of oyster mushroom growth?
Oyster mushrooms follow the same stages: the grow bag turns completely white, pins show within a week after you open it, and the caps are ready as their edges start to flatten (GroCycle). Our timeline has stage times for six species.
What's the difference between primordia and pins?
For a home grower, primordia and pins are the same thing. GroCycle says primordia are what "growers commonly call mushroom pins because they often look like pinheads" (GroCycle).
Do mushrooms need light at every stage?
No: colonizing jars and bags don't need light, but fruiting blocks need some. Cornell says lighting is "not important" during incubation, and "If a book can be read comfortably in the fruiting room space, your lighting should be sufficient" (Cornell). Our pinning guide covers light and pins.