I can’t believe it’s not Butter! The Butter Cap

Sorry for the awful title, but it had to be done! I can’t believe I haven’t made a post on this mushroom before either. Next to the Brown Roll Rim, this has had to have been the most common mushroom I’ve found in great number during autumn/early winter last year (2011).

Often found in woodland in large scattered groups or even as solitary souls, the Butter Cap (Collybia butyracea / Rhodocollybia butyracea*) is a very common edible mushroom (hence being categorised in my ‘Woodland Treats’ blog category) but does not have a particularly pleasurable texture or amazing taste (so I’ve put it in ‘Tales of Toadstools / The Inedibles’ category too).

The texture of the cap, as the common English name suggests, is very smooth, slippery and greasy – not unlike the sensation when you run your finger on some butter… As you do!

To my now ‘trained eye’ they are instantly recognisable. But as you’ll find with experience, the appearance, specifically the cap, can be a very unreliable visual marker for identification due to colour variations. These variations can also be exaggerated due to moisture level and age etc…

The unreliable cap colour can range from dark red/brown, ocherous/buff brown to pale bone-white or ivory (usually with a much darker centre) when older and dryer. Also adding to the confusion is that this species has a common ‘lighter’ variation (Collybia butyracea var. asema) which (I think) is currently under debate. It is generally lighter all round in colour, and I’m making an educated guess that the centre picture below is a good example of this variant.

The shape of the cap and the gills are fortunately more reliable, usually with a shallow dome shape and distinctive raised bump at the centre (or umbo). Sizes in width can differ from small to medium-large (3 – 8cm) and the margin (edge) is lighter than the rest of the cap, sometimes becoming irregular and even ‘wavy’, often showing a faint striated edge (see Mushroom Identifaction Page for more info on Margin/Edge ID features). The gills are crowded, free from the stem and remain white(ish).

But for best identification I always examine the stem. It shares the same brown shade shown on the cap and typically has a slightly thicker base compared to the thin tapering at the apex where it joins the cap. It becomes hollow towards the base which is darker, often covered in fine white down. A little test to confirm identification is to break apart the stem. It is very tough and stringy and you will see also where it is hollow at the base.

You can take a quick ‘smell’ test, but again, I wouldn’t fully rely on this for a good ID tip. It can be very mildly mushroomy or even slighty rancid. So there you go!

Note: As I mentioned earlier, this species is abundant in mixed Woodland throughout autumn to early winter, but while out on a recent foray that they can appear in grassland near woodland, but it doesn’t happen often. The small group I found in November 2011 were of the lighter variety, large and creakily shaped. Obviously they were going mad trying to get themselves back to the woods. Maybe!

*Note: To date, some members of the Collybia family have been moved to new genera due to DNA research and some may have different names. ‘Collybia butyracea’ still seems to be currently used here and there, but technically speaking it is ‘Rhodocollybia butyracea’.

Butter Caps (Collybia butyracea var.asema) abundant in leaf litter in autumn through to early winter. Note the ‘broken apart’ stem base which is covered in fine white down (bottom-left). It is stringy, tough and hollow.