Fungus writing has a bad habit of repeating claims nobody has checked in forty years. Everything here is sourced, and where the popular version has run ahead of the evidence, that's noted rather than tidied away.
How big, how many, how old
2,385 acres
A single genetic individual of Armillaria ostoyae in the Malheur National Forest covers roughly 2,385 acres — about 3.7 square miles. It is estimated to be somewhere between 2,400 and 8,650 years old, and it is mostly underground. What you see above ground are honey mushrooms and dying trees.
US Forest Service surveys, Malheur National Forest, 2000 onward
23,000+ mating types
Schizophyllum commune, the split gill — one of the most widely distributed fungi on the planet, and probably growing on a dead branch near you — has over 23,000 mating types. Nearly any two individuals are compatible. It is the most extreme known solution to the problem of finding a mate while unable to move.
Kothe, 1996; Raper, 1966
7 trillion spores
If every spore from one Calvatia gigantea germinated and grew, the resulting mass would substantially exceed the mass of the Earth. Almost none of them do. This is what a reproductive strategy looks like when individual offspring cost nothing and survival odds are astronomically low.
Buller, Researches on Fungi, 1909–1950
~90% of land plants
Around 90% of land plant species form mycorrhizal associations, trading sugars for water and mineral nutrients. This relationship appears in the fossil record alongside the earliest land plants, and the current view is that plants may not have been able to colonise land without it.
Brundrett & Tedersoo, New Phytologist, 2018
How they actually work
20,000 g acceleration
Pilobolus, the hat-thrower, builds hydrostatic pressure in a stalk and fires its spore packet at accelerations exceeding 20,000 g — reaching about 25 mph within the first millimetre of travel. It does this to clear the ring of ground around dung that grazing animals avoid, landing its spores on grass that will actually be eaten.
Yafetto et al., PLoS ONE, 2008
Fruiting bodies release water vapour, which cools the air immediately around them. That evaporative cooling generates convection currents strong enough to lift spores clear of the still air near the ground — even in a completely windless room. High-speed imaging shows spores being carried upward by air the mushroom itself set moving.
Dressaire et al., PNAS, 2016
Most gilled mushrooms launch each spore individually using a mechanism called Buller's drop: a droplet of water condenses at the spore's base, merges suddenly with a film on the spore surface, and the abrupt shift in the centre of mass flings the spore off its stalk. The distance travelled is roughly a tenth of a millimetre — just far enough to clear the gill and fall free.
Pringle et al., Mycologia, 2005
Lignin — the polymer that makes wood rigid — is chemically stubborn enough that very little can break it down. White rot fungi evolved enzymes that can, and they remain effectively the only organisms doing it at scale. Every rotting log in every forest is being disassembled by something in this group.
Floudas et al., Science, 2012
The genuinely odd ones
~80 known species
Bioluminescent fungi produce a steady green light at around 520–530 nanometres through a luciferin–luciferase reaction, the same class of chemistry fireflies use but independently evolved. Glowing rotten wood was called foxfire and was familiar enough historically to be used, apparently, as a light source in submarine prototypes.
Oliveira et al., Photochemical & Photobiological Sciences, 2012
Ophiocordyceps unilateralis infects carpenter ants and alters their behaviour, driving the ant to leave its colony, climb to a specific height, and clamp onto a leaf vein before dying. The fungus then fruits from the ant's head. Later work found the fungus does not invade the brain at all — it surrounds and manipulates the muscles directly.
Hughes et al., BMC Ecology, 2011; Fredericksen et al., PNAS, 2017
Melanised fungi including Cladosporium sphaerospermum were found thriving inside the damaged reactor, and appear to grow preferentially toward radiation sources. The leading hypothesis is that melanin allows them to derive usable energy from ionising radiation, a process proposed as radiosynthesis. It has been tested aboard the ISS as potential shielding.
Dadachova et al., PLoS ONE, 2007; Averesch et al., 2020 ISS experiment
8 m tall
Prototaxites fossils are trunk-like structures up to eight metres tall and a metre wide, from a period when nothing else on land exceeded knee height. Their classification has been argued over for 150 years. Isotopic analysis supports a fungal or fungus-like affinity, though a 2025 reassessment argues it belongs to no known lineage at all.
Boyce et al., Geology, 2007; ongoing reassessment 2025
What they are related to
Fungi and animals share a common ancestor more recent than the one either shares with plants — both sit within a group called the opisthokonts. Fungi store energy as glycogen, as animals do rather than as starch. The practical consequence is unwelcome: antifungal drugs are hard to develop precisely because fungal cells resemble ours.
Wainright et al., Science, 1993
Chitin — the nitrogen-containing polysaccharide that forms crab shells and beetle carapaces — is also the structural material of fungal cell walls. It is why mushrooms hold their shape when cooked, and why they contain a type of dietary fibre no plant provides.
Standard mycological texts; Webster & Weber, Introduction to Fungi
Having no mouth and no gut, a fungus secretes enzymes into its surroundings, breaks food down externally, and absorbs the dissolved result through its cell walls. Every cultivation problem follows from this: your substrate is an external stomach, and anything else that lands in it is eating your food with the same method.
Basic fungal physiology
Mycorrhizal networks connecting multiple plants do exist and can transfer carbon and nutrients. But the popular framing — trees deliberately feeding their young through fungal networks — outruns the evidence considerably. A 2023 review by researchers including several who did the original work found the strongest claims unsupported by field data. The honest version is still remarkable and less tidy.
Karst, Jones & Hoeksema, Nature Ecology & Evolution, 2023
If one of these turns out to be wrong, it should be corrected rather than repeated. Sources are named above so you can go and look — which is more than most versions of these lists offer.
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