Mushroom of the Month - November 2009

Earthstars are like busses: they keep you waiting for ages and then suddenly a whole host of them arrive at once. We go for years without stumbling across these remarkable fungi and then, when conditions suit them, we have a bumper year (as it seems, in some places at least, we have been enjoying this year). The earthstars shown above are Geastrum triplex, commonly referred to as the 'collared earthstar' because in many instances the arms crack as they bend, with the result that the spore case seems to be sitting on a separate saucer-like layer.

The opening on the top of the spore-sac is pointed at first, and is surrounded by a fuzzy ring slightly paler fawn-brown than the rest of the spore-sac outer surface.

Look in woodland for this member of the (hopelessly jumbled, taxonomically, but useful from an identification point of view) Gastromycetes group. They are most often found under hardwood trees, but we have also found them in coniferous woodland and in parkland under Coast Redwood trees. Collared earthstars are larger than other earthstar species, and they have a spore-sac diameter up to 5cm and arms that span twice that distance when fully outstretched. If you cut through a young fruitbody the interior is white, but it gradually turns into a dark brown powdery mass as the spores mature. Spores are emitted from the apical hole as breezes blow across it, and much larger puffs of spores escape when raindrops hit and compress the spore-sac.

Earthstars are mysterious mushrooms. Why, for example, do some collared earthstars split open with just four rays while others produce five, six, seven or occasionally eight rays? Let us know if you have seen specimens with more than eight rays...

For pictures of more earthstars and other Gastromycetes fungi see www.first-nature.com/fungi/gasteromycetes/