Cornell University

Twinkly earthstars

Aside: Recently I learned that the Library of Congress has added this blog to their historical collection of Science Blogs. I think that’s pretty cool. Thanks for coming along on the ride.

Fungi are lively things, but (like this blog) you can seldom spot them moving. That’s why we like time lapse videos here on the Cornell Mushroom Blog, to hurry things along a bit. Our fungus of the day barely needs speeding up — pleasingly, it’ll do its thing while I share a cup of tea with visitors at my lab table. Drop one in water and in ten minutes it unfolds, revealing a plump center that you can puff with a poke. As it dries, it slowly closes up, ready for teatime tomorrow. A small wonder.

There are two kinds of earthstars that look similar only because they’ve hit upon the same delightful solution for spore dispersal. This one, Astraeus, has the infinite ability to open and close, open and close. Species of Geastrum look like kin, but do their trick just once and remain open for business. Whereas Astraeus earthstars are the sisters of boletes, Geastrum earthstars are relatives of stinkhorns.

I found my Astraeus earthstars among the dunes of Cape Cod, Massachusetts. Then in my local Asian grocery, I found a bright red can from Thailand, marked “Astraeus hygrometricus,” and here you see a photo of its contents in my palm. Astraeus earthstars are a valuable wild mushroom in Thailand, and are picked before they even open up, then sold both fresh and canned. But I’ve never heard of anyone gathering earthstars for dinner here in North America, and it made me wonder.

edible earthstars from ThailandUnlike you, perhaps, I didn’t wonder about what recipe to use for my Cape Cod earthstars (well past their prime; already open and full of powdery spores). No, I wondered what we mycologists often wonder — are those Thai earthstars really the same thing as these American ones? And, not surprisingly, I found that the answer is: No, they are not. So I don’t plan to cook up any American earthstars, because I don’t know whether they are edible. Just because they are in the same genus doesn’t mean they should be (think, Amanita phalloides (deadly) vs. Amanita caesaria (yummy)).

For the longest time, we thought all Astraeus earthstars were the same species, and we called them all Astraeus hygrometricus (the water-measurer; the barometer earthstar). But the littlest thing in biology, under scrutiny, often turns up surprises and intrigues. That’s what Phosri and friends found,2 when a closer look revealed that there are many different lineages of earthstars, and they had to describe some new species to accommodate them all. So now we know that my Cape Cod earthstars are quite different from those you’d eat in Thailand, in both their habitat and their genetic make-up.

A can of Thai starsWhen something you thought you knew needs dividing into many pieces, there’s bound to be issues with names. Practically every Astraeus collected over the last two centuries has been called A. hygrometricus. Now we know most of them are not, which means that only some of the things we thought we knew about this species are actually true. The real Astraeus hygrometricus occurs in France and Turkey. My can of “A. hygrometricus” from Thailand is one of the two Thai species: A. asiaticus or A. odoratus. And what shall we call our American species?

American Astraeus earthstars, so far, seem to be either A. morganii (like mine– plumpish; spores not too bumpy) or A. smithii (littler; warty spores), and I’d bet there are other species too, awaiting discerning eyes. I can sense you groaning at this proliferation of names… but don’t. You don’t need to know the names of every little thing — you can just call them Astraeus if you like, or barometer earthstars. But WE need to have names for every little thing. Not having names for things makes them almost impossible to perceive. They’re genetically different, and they’re probably ecologically quite different in ways we’ve never noticed. Without good names it’s hard to answer important questions like “is it edible?” and “what’s it doing?”

What IS it doing, anyway? Sand seems an improbable place to find fungi. You’ll be pleased to hear that under the shifting sands my Cape Cod earthstars are hooked up to the roots of dune plants, forming friendly relationships (ectomycorrhizae!) that benefit both plant and fungus. Their starry fruits and clever dispersal mechanism help them spread spores that find new seedlings to team up with; new dunes to stabilize.


  1. C. Phosri, R. Watling, M.P. Martín, J.S. Whalley. 2004. The 

genus Astraeus 


Thailand. Mycotaxon 89(2): 453-463.
  2. C. Phosri, M.P. Martín, Roy Watling. Astraeus: hidden dimensions. IMA Fungus 4(2): 347–356. doi:10.5598/imafungus.2013.04.02.13 [use this article to ID your earthstars]

Thanks to Claire Smith for the time lapse video and earthstar photography. Thanks to Lawrence Millman for the good company.

Comments Off on Twinkly earthstars


Comments are closed.


Most people don't pay much attention to fungi, which include things like mushrooms, molds, yeasts, and mildews. Here at Cornell we think they're pretty fascinating. In fact, even the most disgusting foot diseases and moldy strawberries are dear to our hearts. We'd like to talk to you about fungi, so that like us, you too can tell gross stories at the dinner table. Afterwards, maybe you'll notice some things you would have overlooked before, and we think this could be good for the planet.

Kathie T. Hodge, Editor

Beneath Notice, our book of borescopic mycology.


Entries Comments

Or subscribe by email by entering your address: