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Cap surface

Velvety

Velvety — mushrooms with the trait «Velvety»

A velvety, suede-like or finely felted (tomentose, velvety) cap surface is one of the most pleasant textures to the touch in the mushroom world. The cap looks matte, with no shine at all in the sun, and if you run a finger over it, it feels like a piece of fine suede or soft velvet.

This effect comes from microscopic, densely packed upright hyphae (tiny hairs) that stick out from the mushroom's cuticle.

24 species in the database.

The "suede" elite

According to Roger Phillips and M.Ya. Zerova, a velvety cap is most often the calling card of the bolete family (Boletaceae):

1. Xerocomus boletes (Xerocomus / Xerocomellus): Almost all of them (the suede bolete, the ruby bolete, the red cracking bolete) have a perfectly matte, velvety cap when dry.

2. Bay bolete (Imleria badia): In dry weather its dark chestnut cap is the very model of velvetiness. Unlike Xerocomus boletes, though, these tiny hairs stick together in the rain, and the bay bolete becomes slightly tacky.

3. Bronze bolete (Boletus aereus): It has a very dark, blackish-brown cap that often keeps its velvety texture even when mature.

4. Velvet rollrim (Tapinella atrotomentosa): This mushroom, which grows on stumps, has a unique dark brown, incredibly densely velvety (almost plush) stem and a matte cap.

The danger of a velvety texture

A velvety surface is great protection against sunburn. But among gilled mushrooms this feature can be a warning sign.

For example, the poisonous brown rollrim (Paxillus involutus) has a matte, suede-like or finely felted cap surface (especially near the inrolled margin). Some poisonous webcaps have velvety caps, too.

Questions and answers

Why does a velvety cap stop being velvety after rain?
The microscopic hairs (hyphae) that create the suede effect get wet very easily and stick together in water. As a result, the matte surface becomes smooth, shiny and sometimes even slippery (because the water activates polysaccharides in the skin). Once the mushroom dries out, the hairs "fluff up" again and the velvetiness comes back.
Does a velvety cap need to be peeled before cooking?
No, there's no need to peel the skin off velvety mushrooms (such as Xerocomus boletes or bay boletes). This skin doesn't contain bitter slime (as slippery jacks do), it digests perfectly well, and it gives dishes a rich mushroom aroma and color.

Sources

  1. 1.Зерова М.Я. та ін. Визначник грибів України. 1979
  2. 2.Roger Phillips. Mushrooms (Roger Phillips)
  3. 3.David Arora. Mushrooms Demystified
  4. 4.Index Fungorum