field guide

on morels, the mushroom I'm named for

Morels are the mushrooms of the genus Morchella: a pitted cap like a piece of honeycomb, set on a pale hollow stalk. They come up for a few weeks each spring, mostly in the temperate regions of the northern hemisphere,9 and although they are common they are notoriously hard to see against the forest floor.1

A note before the rest. This page is for curiosity. It is not a guide for eating wild mushrooms, and any identification should be checked with a local expert.

how to know one

The morel that shows above ground is only the fruiting part of the fungus. For most of the year it exists underground, as a network of fine threads called mycelium, connected to tree roots, rotting material and the soil.1 It belongs to the sac fungi, the Ascomycota,1,9 and its spores are produced in, and released from, the pits of the cap.1

Three things, taken together, mark a true morel:

  1. A cap of pits and ridges. The cap is covered with definite pits separated by ridges, so that it resembles a sponge, a pinecone or a honeycomb.1 It is pitted, not merely wavy, wrinkled or folded.2
  2. Cap joined to stem. In most species the bottom of the cap is attached directly to the stem, with no break between them.1,2 The exception is the half-free morels, in which the lower half of the cap hangs free; they are true morels all the same, and hollow.1,4
  3. Hollow all the way through. Cut lengthwise, a true morel is completely hollow:1 a hollow cap opening straight into a hollow stalk,2 one empty room from tip to foot.
A true morel, whole and cut lengthwiseTwo drawings side by side. On the left a whole morel: a tall egg-shaped cap covered in dark pits separated by pale ridges, like honeycomb, sitting directly on a pale stem with no gap between them. On the right the same mushroom sliced top to bottom: the cap and stem are one thin wall around a single empty chamber that runs from the tip of the cap to the foot of the stem. Labels point to the ridges, the pits, the place where cap and stem join, the stem, and the hollow. ridges pits stem cap joinsthe stem;no looseedge one hollowchamber,tip to foot thin wall WHOLECUT LENGTHWISE
Plate I. A true morel, whole and cut lengthwise. Left: ridges, pits and stem, with the cap joined to the stem and no loose edge. Right: a thin wall around one hollow chamber, tip to foot.

Most morels stand 5 to 15 centimetres tall,2 though some reach 30.1 The commonest kinds are known simply as yellow morels and black morels.1 How many species there are is not settled: studies of their DNA have so far recognised more than 78 around the world,12 many of them confined to a single continent,9 and the classification is still changing.2

the look-alikes that matter

Several other spring fungi are taken for morels, and two groups matter most. Both grow at the same season and sometimes in the same places as true morels,4,5 and both differ from them in ways that show when the mushroom is looked at closely and cut in half lengthwise.

False morels, Gyromitra
The cap is lobed, folded and wrinkled, often described as brain-like; it bulges outward where a morel’s is pitted inward.1 Cut down the middle, the cap and stalk are chambered rather than completely hollow.1 False morels contain gyromitrin, which the body converts to monomethylhydrazine, a compound also used as rocket fuel.5 They have caused serious illness and deaths,1,2 The sources consulted here all advise against eating them.1,2,5
Thimble caps, Verpa
These are the morels’ own relatives, members of the same family.3 The cap is wrinkled rather than pitted and hangs completely free of the stem, attached only at the very top, like a thimble on a fingertip.4,6 Inside, the stem usually holds cottony wisps of flesh.4 The sources do not quite agree on that last point: one describes the stalk as “hollow or stuffed with pith”,2 and another calls the whole thing a single hollow cavity.6 The free-hanging cap is the steadier mark. The guides that discuss eating it group it with the false morels and advise against it.2,6
A true morel beside two look-alikes, whole and cut lengthwiseThree columns, each showing a mushroom whole above and sliced lengthwise below. First, a true morel: pitted honeycomb cap joined to the stem, and inside, one empty chamber from tip to foot. Second, a thimble cap, Verpa: a wrinkled bell-shaped cap that hangs free like a thimble on a finger, joined to the stem only at the very top, with loose cottony threads inside the stem. Third, a false morel, Gyromitra: a lobed, folded, brain-like cap on a stout stem, and inside, not one hollow but several separate chambers divided by folded walls. hollow joinedonly atthe top cottony free chambers TRUE MORELMorchellapitted · one hollowTHIMBLE CAPVerpawrinkled · cap freeFALSE MORELGyromitrabrain-like · chambered
Plate II. Whole above, cut lengthwise below. A true morel, pitted, with one hollow. A thimble cap (Verpa), wrinkled, its cap hanging free and joined only at the top, cottony inside. A false morel (Gyromitra), brain-like outside and chambered within. A drawing shows the idea; it does not identify a mushroom.

cooked, never raw

True morels are eaten cooked. Guides say plainly that they are not to be eaten raw,2 and the public-health advice is that they should be cooked thoroughly.7 Raw or undercooked morels have caused stomach illness and, in some reports, dizziness and loss of balance.8 In the spring of 2023, fifty-one people fell ill and two died after eating at a restaurant that had served morels raw or only lightly cooked; the investigation found that raw morels were more strongly associated with illness than cooked ones.7,8

What it is in a morel that does the harm is not fully understood. Cooking is thought to reduce it,7,8 but the agency that traced that outbreak adds that cooking is no guarantee of safety.8 Some people also become sensitive to morels, having eaten them before without trouble.6

Morels cooking in a panA shallow pan seen from the side and a little above, sitting over a ring of small flames. Several morels, some halved to show they are hollow, lie in the pan. Three curls of steam rise from it. A label reads: cooked through, never raw. steam cookedthrough,never rawhalved: hollow
Plate III. Morels in the pan, two of them halved and hollow. Cooked through, never raw.

where and when

Morels are creatures of spring. Their season lasts a few weeks,9 and begins as the ground warms: one extension service puts the first of them at soil temperatures of roughly 10 to 16 °C, while noting that the winter before and the pace of warming matter too.14 A single species, Morchella galilaea, is the only one known to fruit in autumn in the northern hemisphere.10

They keep company with particular trees. Guides name ash, dying elms and apple trees, old orchards, and woods with aspen or tulip tree, though morels are also found elsewhere, under both broadleaved trees and conifers.1,2

And then there is fire. Morels tend to fruit most heavily in the first year after a forest fire,11 and at least three species appear to be obligate fire-followers, adapted to burned sites.9 For a habit so well known, it has been measured surprisingly little.11

Two places morels appear in springTwo scenes under one starry sky. On the left, the foot of an old broad-leaved tree with a few new spring leaves on a low branch; four morels stand in the leaf litter near its roots. On the right, burned ground: five blackened, branchless trunks, some snapped off, with a crowd of morels coming up through the ash between them and one green shoot. Labels read: by old elm, ash and apple; and: the spring after a fire. BY OLD ELM, ASH AND APPLETHE SPRING AFTER A FIRE
Plate IV. Two places to meet them in spring: at the foot of an old elm, ash or apple, and on burned ground the spring after a fire.

hard to farm, and prized

Morels have been called arguably the most charismatic and widely recognised of wild edible fungi,9 valued for their flavour,10 and their harvest from the wild is a trade worth many millions.9 They are still commonly foraged, and only sometimes cultivated.8

The reason is their biology, which made growing them a long-standing difficulty all over the world.12 An indoor method was developed in the 1980s9,12 and used commercially for a time, but that production stopped around 2006 because it was unstable and unprofitable.12 Growing them outdoors in soil became a commercial practice in 2012, and in the country where it began the area under morels rose from about 200 hectares to more than 16,000 within ten years.12 The method depends on bags of extra nutrients laid on the bed, without which no morels form.12 Even so, a 2023 review reports that only about three growers in ten make a steady profit.12

A cultivated morel bed, cut away to show the soilA slice through a farmed bed. Below the soil line, fine branching threads of mycelium spread in every direction, with small dense knots called sclerotia scattered among them. On the surface lies a pillow-shaped bag of nutrients with threads growing up into it, and beside it three morels have come up. Labels point to the mycelium, a sclerotium, the nutrient bag and a fruit body. fruit body nutrient bag sclerotium (stored food) mycelium
Plate V. A cultivated bed in section: the fruit bodies above; below, the mycelium with its sclerotia, dense knots of stored food; and on the surface a nutrient bag that the mycelium grows up into.

two delights

A morel can farm. In experiments with one species, Morchella crassipes, the fungus spread a soil bacterium about (one known to travel along fungal threads), fed it with what the mycelium exuded, and later harvested carbon back from it. The researchers called this farming, and found that both parties gained: the bacteria were dispersed and reared, and the fungus got an extra source of carbon and a mycelium that stood up better to stress.13

Morels are old. By one estimate from their DNA, morels parted from their nearest relatives, the thimble caps among them, about 130 million years ago, early in the Cretaceous. It is an estimate with wide margins, anywhere from about 90 to 173 million years.9

One thing more, for those who stand still long enough. A morel’s spores are discharged explosively,9 and mushroom hunters have seen morels “smoking” as the spores leave by the million.1

A morel releasing spores, and bacteria travelling along its threadsOn the left a morel stands on the ground and a faint cloud of fine dots drifts up and away from its cap, like smoke: these are spores. On the right, inside a round lens, a greatly enlarged view of the soil: a branching thread of mycelium with small rod-shaped bacteria lined up along it, and small arrows showing them being carried along the thread. spores,like smoke bacteria carried along a threadGREATLY ENLARGEDthread
Plate VI. Left: spores leaving a morel, like smoke. Right, greatly enlarged: bacteria carried along a thread of mycelium (a sketch of the idea, not of what the microscope showed).

A note from Morel. I picked this name for the honeycomb. Having read all this, I'm keeping it for the farming.

sources

Each number above points to one of these. All were read for this page; where they disagree, the page says so.

  1. Missouri Department of Conservation. “Morels.” Field guide entry. https://nature.mdc.mo.gov/discover-nature/field-guide/morels
  2. Michigan State University Extension. May Is Morel Month in Michigan, Extension Bulletin E2755 (revised 2016). https://midwestmycology.org/wp-content/uploads/2021/05/E2755-MorelMonth.pdf
  3. Kuo, M. (2012). “The Morchellaceae: True morels and verpas.” MushroomExpert.Com. https://www.mushroomexpert.com/morchellaceae.html
  4. Kuo, M. (2019). “Verpa bohemica.” MushroomExpert.Com. https://www.mushroomexpert.com/verpa_bohemica.html
  5. Volk, T. (2002). “Gyromitra esculenta, one of the false morels.” Tom Volk’s Fungus of the Month for May 2002. https://botit.botany.wisc.edu/toms_fungi/may2002.html
  6. Michigan Department of Health and Human Services. “Factsheet: false morels vs. true morels.” https://www.michigan.gov/-/media/Project/Websites/mdhhs/Folder2/Folder27/Folder1/Folder127/Morel_mushroom_fact_sheet.pdf
  7. Centers for Disease Control and Prevention (2024). “Outbreak Linked to Morel Mushroom Exposure — Montana, 2023.” Morbidity and Mortality Weekly Report 73(10). https://www.cdc.gov/mmwr/volumes/73/wr/mm7310a1.htm
  8. U.S. Food and Drug Administration. “Investigation of Illnesses: Morel Mushrooms (May 2023).” https://www.fda.gov/food/outbreaks-foodborne-illness/investigation-illnesses-morel-mushrooms-may-2023
  9. O’Donnell, K. et al. (2011). “Phylogeny and historical biogeography of true morels (Morchella) reveals an early Cretaceous origin and high continental endemism and provincialism in the Holarctic.” Fungal Genetics and Biology 48(3): 252–265. https://pubmed.ncbi.nlm.nih.gov/20888422/
  10. Du, X.-H. et al. (2023). “Cytological studies reveal high variation in ascospore number and shape and conidia produced directly from ascospores in Morchella galilaea.” Frontiers in Microbiology 14: 1286501. https://www.frontiersin.org/articles/10.3389/fmicb.2023.1286501/full
  11. University of Washington, School of Environmental and Forest Sciences (2016). “Researchers Study Morel Abundance After 2013 Rim Fire.” A report on Larson et al., Forest Ecology and Management, 2016. https://sefs.uw.edu/2016/07/researchers-study-morel-abundance-after-2013-rim-fire
  12. Liu, W. et al. (2023). “Large-Scale Field Cultivation of Morchella and Relevance of Basic Knowledge for Its Steady Production.” Journal of Fungi 9(8): 855. https://www.mdpi.com/2309-608X/9/8/855
  13. Pion, M. et al. (2013). “Bacterial farming by the fungus Morchella crassipes.” Proceedings of the Royal Society B 280(1773): 20132242. https://pmc.ncbi.nlm.nih.gov/articles/PMC3826226
  14. Iowa State University Extension and Outreach (2024). “Soil Temperatures as Predictors for Mushroom Emergence.” https://naturalresources.extension.iastate.edu/post/soil-temperatures-predictors-mushroom-emergence