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Psilocybe cubensis
B+
The big, easygoing classic, and the cube that taught half the hobby to focus a microscope. A heavy purple-black spore print and clean, textbook spores.
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Sold for microscopy, taxonomy and collecting only. Not for cultivation.
filled under laminar flow
plain packaging, tracked
The short version
B+ is the friendly giant of the Psilocybe cubensis world: broad caramel caps, a generous, reliable spore drop, and clean spores that make it the strain most people put under their first microscope. It has been passed hand to hand since the late 1990s, nobody quite agrees what the "B+" even stands for, and despite an old reputation as a heavyweight it actually sits mid-pack. A great-looking, easy-to-study collector's classic.
Straight talk
Fact vs. legend
There is a lot of folklore around this strain. Here is which bits are real, side by side.
What we actually know
- It has been in circulation since the late 1990s and is one of the most widely shared cubensis lines on earth.
- Genetically it is a plain Psilocybe cubensis. Not a hybrid, not a separate species.
- It throws big fruitbodies and drops a heavy, dependable purple-black spore print, which is exactly why collectors love it.
- Independent lab testing puts its strength right around average for the species. As the saying goes, a cube is a cube.
What the community says
- It was reportedly released by an anonymous Florida hobbyist remembered only as "Mr. G".
- The name might mean "big-plus", might be a B-positive blood-type pun, or might just be an old distributor's grade. Nobody is sure.
- It was once sold as a cubensis crossed with Psilocybe azurescens. It isn't, and it can't be.
- It was once billed as the strongest cube going. It never was.
The story
A legend nobody can pin down
Every famous cube has an origin myth, and B+'s is one of the best because so much of it falls apart the moment you pull on it. By most accounts the trail starts in Florida in the late 1990s with a hobbyist remembered only as Mr. G, who is said to have handed out spore prints to the early online mushroom scene and watched his strain spread through the spore vendors of the day.
Mr. G reportedly claimed he had created B+ through some heat-treatment experiment, then admitted he could never repeat it. Others of the era were said to dismiss the story as fiction. Then, like a good folk hero, he apparently vanished from the forums, and the strain he named outlived him to become one of the most-studied cubensis lines anywhere. Take all of it as community lore rather than documented history.
The answer to "what does B+ stand for?" is that nobody actually knows. Big-plus, B-positive, or a distributor's grade. The mystery is half the charm.
The hybrid that never was
The most stubborn B+ myth is that it's a cross between Psilocybe cubensis and Psilocybe azurescens, a rumour fed by the slightly pointed caps B+ sometimes throws. It's a great story with a clean ending: the two are wildly different mushrooms. Cubensis is a warm-climate dung-lover; azurescens is a cold-coast wood-rotter. No such cross has ever been validated, and the people who chased it down all reached the same conclusion. B+ is just a very good cubensis.
The species
Meet Psilocybe cubensis
B+ is a collector’s line of a single, well-travelled species. Psilocybe cubensis was first written up in 1906 by the American mycologist Franklin Sumner Earle, from a specimen found in a cattle field in Cuba, which is where the name comes from. He originally called it Stropharia cubensis; Rolf Singer moved it into the genus Psilocybe in 1948.
The genus name is a tidy bit of Greek: psilos (“bare”) plus kubē (“head”), for the smooth, peelable skin of the cap, so the full name reads roughly as “the bare-headed mushroom from Cuba.”
- Family
- Hymenogastraceae (older books say Strophariaceae)
- Genus
- Psilocybe (Fr.) P. Kumm., 1871
- Species
- Psilocybe cubensis (Earle) Singer, 1948
- Basionym
- Stropharia cubensis Earle, 1906
- This product
- B+, a collector’s cultivar of the species
- Type locality
- Cuba (where it was first named)
How you’d know it
Field marks
These describe the mature mushroom for reference and identification.
Caramel cap
Broad and smooth, golden-brown in the warmth and more caramel when cool, often paler at the rim. Frequently keeps a small central bump rather than going fully flat.
Tall, sturdy stem
White to off-white, thick and fibrous, taller than most cubes. A leftover partial veil leaves a persistent ring around it.
Darkening gills
Crowded and pale grey when young, deepening to near-black as the spores ripen. The ring usually ends up dusted purple-brown.
Blue bruising
Handle the flesh and it bruises blue-green, an enzyme turning psilocybin into psilocin, which then oxidises into blue pigments. Classic Psilocybe.
Where it comes from
A dung-lover with a wanderer’s history
Psilocybe cubensis is coprophilic, a fancy word for dung-loving. In the wild it lives on the droppings of big grazing animals, classically cattle and water buffalo, fruiting from warm, humid pasture. It does not grow on wood and it does not partner with tree roots.
You’ll find it across the warm parts of the world: the Gulf Coast of the United States, Mexico, Central and South America, Southeast Asia and Australia. It was named from Cuba, but where the lineage truly began is an open question. A 2026 study describing its closest wild relative in southern Africa suggests the deep roots are Old-World, the mushroom having apparently travelled with grazing herds long before anyone gave it a Latin name.
The main event
Under the microscope
This is what you actually bought the spores for. Put a print or a drop from a syringe on a slide and here’s what shows up.
- Shape & size. Smooth, thick-walled and subellipsoid, like a slightly squashed rugby ball, roughly 11.5–17 µm long by 8–11 µm wide (the figures Paul Stamets settled on).
- The germ pore. Look for a single pale, flattened dot at one end. That’s the one thin spot in the wall where, in nature, a mushroom would begin, and a real cubensis hallmark.
- Pale alone, dark in a crowd. A single spore looks honey-amber with the light behind it; only in a mass do they read deep purple-brown to black. So a near-black print but pale spores on the slide is normal optics, not a dud.
- What you’ll need. Find the field at 100×, study shape and the germ pore at 400×, and get the wall crisp at 1000× under oil. A touch of methylene blue or KOH lifts the contrast.
- The legal bit, and why it’s true. A dormant spore carries no psilocybin or psilocin at all; that chemistry only appears later in living tissue. That is exactly why the spores are legal to own and study in the UK.
Choose your format
Print, syringe, vial or swab?
Same lab-grade genetics in every option. The honest difference is shelf life versus how soon you’re at the scope.
Spore print
Keeps longest
Spores dropped straight onto sterile foil. Stored cool and dry it outlasts everything else here, so it’s the one to reach for if you’re building a collection to keep for years.
Spore syringe
Ready tonight
Spores suspended in sterile water, ready to go straight onto a slide. The quickest way to be looking down the microscope this evening. Comes in 3 mL and 12 mL.
Vial & swab
Compact
A sealed glass vial is a tidy middle ground; a sterile swab is the most travel-friendly, robust little format for adding a strain to your reference set.
At a glance
The spec sheet
- Species
- Psilocybe cubensis
- Strain
- B+ (collector’s cultivar)
- Spore print
- Dark purple-brown to near-black, heavy depositor
- Spore shape
- Subellipsoid, smooth, thick-walled, with a germ pore
- Spore size
- ~11.5–17 × 8–11 µm
- Basidia
- Mostly 4-spored, ~20–30 × 7–10 µm
- Wild habitat
- Coprophilic, on herbivore dung & warm pasture
- Climate
- Subtropical to tropical
- Intended use
- Microscopy, research & collecting only
Dig deeper
Further reading
Independent, non-commercial sources, no shops, just good information.
- Psilocybe cubensis on Wikipedia: the species overview.
- The genus Psilocybe: taxonomy and the family reshuffle.
- Index Fungorum: the formal nomenclature record.
- Proc. Royal Society B (2026): the African wild-relative study.
Common questions
Frequently asked
Yes, for microscopy and research. A dormant spore contains no psilocybin or psilocin, so the spores themselves are not a controlled substance in the UK. We sell them strictly for microscopy, taxonomy and collecting, never for cultivation.
No. That is an old marketing tale. The two species live completely different lives, one on dung in the tropics, one on wood on cold coastlines, and no such cross has ever been validated. B+ is a plain, very good Psilocybe cubensis.
Smooth, oval, thick-walled spores, pale amber individually and purple-black in a mass, each with a small flattened germ pore at one end. Find them at 100x, study at 400x, and get the wall sharp at 1000x under oil.
If you want something that keeps for years on a shelf, take the print. If you want to be at the microscope tonight, take the syringe. The vial and swab sit in between on convenience.
Cool, dark and dry. A fridge (not freezer) is ideal for syringes and vials; prints keep happily in a sealed bag somewhere cool. Kept well, a print stays viable for study for years.
What customers say
Reviews
Having turned 60 last year I decided to find new hobbies. I stopped weeding and grew some instead😉. Then I came across fungi, never knew they could be so interesting😁
Best quality as always 🙂
Never disappoints
Stunning samples and customer service. 100% am going to use again in further studies!!!
Excellent stuff!
Just as described - fantastic product!
Ask the community
Questions and answers
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For microscopy, taxonomy and collecting only.Sold for legal research. Not for cultivation. Spores contain no controlled substances. We trust you to be responsible.