The Collared Earthstar—A Study

Colony of earthstars amid decaying cedar logs, Trent Nature Sanctuary, ON (photo by Nina Munteanu)

It was last spring when I first entered the swamp forest in the Trent Nature Sanctuary. I took the lower east trail that wound through a mature cedar-birch forest. A light breeze caressed the canopy in a soft hush as I walked the spongy layer of cedar duff and loam. Curious to see more, I left the trail and plunged into a chaos of lichen-covered twigs, fallen logs, and mossy boulders. Ferns thrust up through the leaf litter, creating frothy stands of brilliant green. 

I felt like I’d entered an enchantment. Perhaps I had…

…Because, soon after I entered the dark aromatic forest, my heart thrilled with the excitement of an explorer. When I saw the two large decaying cedar logs, trees rooted on them and covered in a thick layer of moss, I struck toward them, camera and tripod clutched in my hands. 

Within moments, I was crawling on all fours over one crumbling cedar log, peering closely at moss and layers of partially decaying wood. Young cedar trees grew out of the old dead tree. I stumbled from one log to the other, camera capturing moss, leaves and decaying wood. Then I saw them: puffballs! Dozens of them clustered throughout the depression between the logs and on the logs. 

Collared earthstar (Geastrum triplex) in leaf litter and moss of Trent Nature Sanctuary, ON (photo by Nina Munteanu)

Each sand-coloured papery spore sac sat on a filigreed star-shaped base with its puckered “mouth” pointed up to the heavens. I couldn’t help myself; reverting to my child-self, I poked one of the spore sacs. The sac, which felt like thin rice-paper, caved and—to my delight—emitted a puff of dark brown spores.

I later learned that this puffball is called the collared earthstar, Geastrum triplexGeo means earth and astrum means star. The species name triplex, which means ‘having three layers,’ refers to the way the ‘star’ arms of the outer layer crack when they peel back, making it look like the spore-sac is sitting on a dish. Spores escape from the apical pointed hole (peristome) as breezes blow across it. Much larger puffs are released when raindrops hit and compress the spore-sac—or an interfering finger depresses the sac. What escapes is a powdery gleba (which distributes the tiny spores). The sides of the peristome ‘beak’ are fibrous and appear slightly ragged.

Life Cycle 

The earthstars I saw were survivors from the previous early winter when they first emerged. These puffballs are visible year round, but will manifest in distinctly different stages over the course of their development. New earthstars emerge and develop in late summer and autumn through into winter. The matured fruiting bodies will survive the winter to be discovered the following spring by curious explorers like me. This spring, I recognized a particular pair that I’d photographed last spring; they were still there, looking the same. Had they survived two winters already? 

According to the Missouri Department of Conservation, Earthstars spend most of the year as a network of fungal cells (mycelia) that penetrate the soil and digest decaying organic material. When they are ready to reproduce, the mycelium develops the “earthstar” above ground.

A. early earthstar bulbs emerge in autumn; B. outer layer peels away, revealing spore sac; C. peeled back outer layer forms a ‘star’ that cracks into a dish-like layer; D. older spore sac and reticulated outer layer next spring

After a late summer / autumn rain, the collared earthstar emerges from the leaf litter looking like a Hershey’s kiss or a fancy bulb-shaped truffle dusted in fine cocoa. Only the outer layer (exoperidium) is visible, peeking out of the litter and loam. The outer layer eventually cracks open, looking like a coconut husk and splits into five to seven ‘arms’ to form a star. Inside is revealed a tan to grey-coloured spore-sac (endoperidium) with a fringed beak (peristome) and its opening (ostiole). The star arms peel back and down, eventually cracking to form the ‘saucer’ which the round fruiting body (spore sac) sits on. The spore sac contains a mass of spores, called the gleba, and fertile mycelial tissue that is white and firm when young, but turns brown and powdery as it ages. Over time, the outer layer of ‘stars’ (exoperidium) form a reticulated pattern of cracks and fissures that deepen into golden-brown colours as they decompose and curl downward to lift the spore-sac farther up. The sac also grows more pale and papery. 

Three stages of development of Earthstar fruiting body from bulb to star (photo by Nina Munteanu)

However, in the rain, the sac reverts to a rubbery consistency and deepens to a dark shiny tan colour. I was surprised by its elasticity; this time when I poked it, the sac sprang back to its round sphere like a thick balloon. 

Earthstar pair during wet weather and dry, Trent Nature Sanctuary, ON (photos by Nina Munteanu)

Habitat

I also learned that the collared earthstar prefers a habitat of leaf litter in deciduous woods, especially beech on chalky soils. However, researchers acknowledge that the collared earthstar is also found under coniferous trees, especially on sloping ground—which better describes where I found them, in this cedar-birch forest. Geastrum triplexis a saprobic organism: it gets its nutrients from decomposing organic matter—such as well-rotted cedar trees, where humus has accumulated—by further breaking down the organic matter then, in turn, returns those nutrients to the soil to complete the cycle. 

Earthstars brave snowfall in winter, Trent Nature Sanctuary, ON (photo by Nina Munteanu)

Human Connections    

The Native American Blackfoot call the earthstars ka-ka-toos, which means ‘fallen stars.’ They believe them to indicate supernatural events. The earthstar is also used in traditional medicines of the Chinese and Native American cultures. The fruit bodies of Geastrum triplex have been chemically analyzed and shown to contain a number of bioactive chemicals. Various chemical derivatives of the fungal sterol ergosterol have been identified along with several fatty acids. The earthstar is used in traditional Chinese medicine to reduce inflammation in the respiratory tract and to staunch bleeding and reduce swelling. The Cherokee put fruit bodies on the navels of babies after childbirth until the withered umbilical cord falls off: as prophylactic and therapeutic measure.

My poking finger triggers a puff of dark brown spores from the Earthstar spore sac (photo by Nina Munteanu)
Boardwalk through cedar birch forest during rainfall, Trent Nature Sanctuary, ON (photo by Nina Munteanu)

References:

Ellis JB, Ellis MB. 1990. “Fungi without Gills (Hymenomycetes and Gasteromycetes): an Identification Handbook. ”Chapman and Hall. London. ISBN 0-412-36970-2.

First Nature. “Geastrum triplexJungh.—Collared Earthstar” Online: https://www.first-nature.com/fungi/geastrum-triplex.php

Kirk, Paul M., Paul F. Cannon, David W. Minter and J. A. Stalpers. 2008. “Dictionary of the Fungi.” CABI, 2008

Kuo M. 2008. Geastrum triplexMushroomExpert.Com

Roody WC. 2003. “Mushrooms of West Virginia and the Central Appalachians.” University Press of Kentucky, Lexington, KY. p. 443. ISBN 0-8131-9039-8.

Torpoco V, Garbarino JA (1998). “Studies on Chilean fungi. I. Metabolites from Geastrum triplex Jungh”. Boletin de la Sociedad Chilena de Quimica43 (2): 227–29.

Woodland Trust. “Collared Earthstar.” Online: https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/fungi-and-lichens/collared-earthstar/

Pegler, D.N., Laessoe, T. & Spooner, B.M. 1995. “British Puffballs, Earthstars and Stinkhorns.”Royal Botanic Gardens, Kew. 

Nina Munteanu is a Canadian ecologist / limnologist and novelist. She is co-editor of Europa SF and currently teaches writing courses at George Brown College and the University of Toronto. Visit www.ninamunteanu.ca for the latest on her books. Nina’s bilingual “La natura dell’acqua / The Way of Water” was published by Mincione Edizioni in Rome. Her non-fiction book “Water Is…” by Pixl Press(Vancouver) was selected by Margaret Atwood in the New York Times‘Year in Reading’ and was chosen as the 2017 Summer Read by Water Canada. Her novel “A Diary in the Age of Water” was released by Inanna Publications (Toronto) in June 2020.

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