Welcome back to Mushroom Monday, your weekly look at some of PEI’s fascinating fungi. We’ve reached the end of mushroom season – and this series – for another year, so let’s go out with a bang! Meet the strikingly beautiful Blue Roundhead (Stropharia caerulea).
I’m fascinated with colourful mushrooms. In plants, colours serve specific purposes. For example, green chlorophyll makes food from sunlight, red pigments act as sunscreen, bright colours attract pollinators, and drab hues hide seeds from predators.
But mushrooms don’t care about photosynthesis, pollination, or seeds, and most get all the UV protection they need from brown melanin. So why are some colourful? How do they appear to animals that perceive colours differently than we do? Does that matter? So many questions!
The amazing complexity of fungi, combined with the mysteries of fungal colours, means I was very excited to see a blue mushroom recently. I thank Dianne Thompson for contacting me about this interesting species!
In my last Mushroom Monday post, I described the limitations of fungal field guides and why they don’t include all the species in an area. None of my guides included Blue Roundhead, but local mushroom expert Ken Sanderson was quick to identify it for me (thanks, Ken!). I’m happy to add this to the growing list of mushrooms that I now know.
I do note that Blue Roundhead is very similar to Verdigris Agaric (Stropharia aeruginosa), and it takes a microscope to reliably tell these two species apart. The Agaric (no relation to Fly Agaric I featured here: https://www.pei-untamed.com/post/fly-agaric) is more likely to be found in woodlands rather than in the garden woodchips where these Blue Roundheads were. I did collect specimens to send for DNA analysis and will update this post if it reveals anything interesting.
Blue Roundheads are well-named. From above, the young mushrooms have round, blue-green or pastel blue caps that are wet-looking and a bit sticky to the touch. As the caps are exposed to sunlight and air, they start changing colour and (to me) begin to resemble an interesting pebble.
Underneath the cap, a delicate partial veil covers and protects the young gills until they are ready to release their spores. Young stems are bluish-white and scaly below the spot where the veil meets the stem, although stems of older mushrooms are sometimes smoother.
Blue Roundhead is a saprophyte that can be found growing in grassy areas and woodchip mulch. Unlike some fungi that form relationships with the living plants around them, saprophytes are decomposers that do the important job of breaking down dead organic matter into component parts that can be reused by other organisms. In this way, they provide essential waste disposal and recycling services.
Scientists have grown Blue Roundhead mycelia – the underground, thread-like network that makes up the main body of a fungus – to better understand how fungi interact with mycelia of other species and their environment. This has painted a picture of fungal warfare among different species, with tactics including invasion of territory already colonized and defensive perimeters created by those being invaded.
It’s also revealed different foraging strategies among different species of fungi. Some spread quickly and are better adapted to finding large hotspots of nutrients (such as a fallen tree). Others – including Blue Roundhead – take a more measured approach and make better use of the smaller amounts of nutrients more evenly spread throughout the environment.
We’ve looked at more than three dozen local species of fungi so far, and there are many hundreds more to go! I’ll bring back Mushroom Mondays next year but will be switching to my Wildlife Tracks & Sign series over the winter. Tracking is a great way to get to know your neighbours of other species on PEI untamed!
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