Sweetbread Mushrooms

Welcome back to Mushroom Monday, your weekly look at some of PEI’s fascinating fungi. It’s often helpful to use more than just sight when identifying mushrooms, and today’s species has a very distinctive smell. Meet Sweetbread Mushroom (aka The Miller, Clitopilus prunulus).

I confess that I generally don’t pay much attention to small mushrooms with white caps and gills. I’m sure they’re perfectly lovely, but I tend to assume they exceed my limited identification skills. After passing by these Sweetbread Mushrooms every day for more than a week, I finally gave in and took a closer look.

One sniff will tell you this mushroom has something different going on. It’s sometimes called ‘The Miller’ because mycologists describe the scent as ‘farinaceous’, like flour or a grain mill. To me, it smells like watermelon rind. That clue was enough to encourage me to look further.

The cap of younger Sweetbread Mushrooms can be smooth and circular (top right photo), although the edges tend to become wavy and irregular with age. Look beneath the cap and you’ll see the edge is rolled under, and there are white (sometimes pinkish) gills running partway down a thick stem (main photo). This mushroom is solid white inside and doesn’t change colour when cut or bruised (middle right photo).

Sweetbread Mushrooms are edible, but there are some close lookalikes on the Island, including the toxic Fool’s Funnel (Collybia rivulosa). The smell of Sweetbread Mushrooms was enough to deter me from trying them, but if you’re inclined to give them a taste, I encourage you to confirm identification with a spore print.

To do this, place one or more of the caps gill-side-down and cover with a bowl to prevent them from being disturbed (or, in my case, to keep the cats from batting them around!). I like to use a surface that’s half light and half dark so that the spores will show up well regardless of colour. Leave the set-up for several hours (or overnight) and then carefully pick up the cap(s) to see the result.

Edible Sweetbread Mushrooms leave a pinkish spore print (bottom right photo) while the spores of toxic Fool’s Funnel are white. Spore print alone is not enough to confirm identification of Sweetbread Mushrooms: you want to ensure that your specimens also match the full physical description and have the characteristic smell.

Sweetbread Mushrooms have been recorded from all three counties on PEI and can be found in grassy or mossy areas under conifer or mixedwood forests; those shown here were on a grassy path through old field White Spruce. They are saprobes – breaking down dead organic matter and acting as nature’s clean-up crew – but may also form mutually-beneficial relationships with nearby trees.

The edible and delicious King Bolete (aka Porcini, Boletus edulis clade) is said to be associated with Sweetbread Mushrooms, and I did indeed find some Kings nearby. As with many of our fungi, fall is the best time to find both those species on PEI Untamed!