Based on the information in Wikipedia - Chestnut Mushrooms and the answer located here at What are the mushrooms used in this (video) recipe? I would take an educated guess that since the chestnut mushroom is brown and not as fully matured (or big) as the portabella mushroom that it must be a baby portabella mushrooom, or the mushroom between a white mushroom and a portabella mushroom.

I am not entirely sure myself since there seems to be numerous aliases to these mushrooms and I can't seem to find a website that lists all the aliases to these mushrooms.

3 Answers 3


Agaricus bisporus is commonly found in two varieties a brown and a white variety both of them have a variety of aliases as you have already found out ... and the name portobella is used for mature fruiting bodies of both varieties. So you can find the brown variety in all sizes from tiny "button" mushrooms over closed and open small and big non-mature fruiting bodies to the big open mature portobellos.

The brown-capped variety will be (at least somewhat) brown through all stages and the white-capped one will have a white cap through all stages. While maturing the gills will turn from white to brown in all varieties, as brown is the color of mature spores in this mushroom species.

Anyway, your assumption is correct - that the chestnut mushroom is in fact a baby (=immature fruiting body) brown-capped portobello mushroom.


According to the wbsite, Australian Mushrooms, https://australianmushrooms.com.au/tips-tricks-facts/ ,the Portobello is just an aged Agaricus bisporus, whereas the Chestnut mushroom is an Agrocybe aergerita

One of the oldest species in the world, first cultivated by the Ancient Greeks. Light brown cap that sits open on the end of a slender, long, creamy-coloured stalk. Firm texture and strong, nutty flavour.


I am given to understand that white or brown buttons will grow into brown cremini and further into brown adult Portobello's

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    I’m afraid that this isn’t entirely correct - white caps will stay white through all stages and brown ones stay brown. So white buttons won’t mature into brown Portobellos.
    – Stephie
    Commented Sep 8, 2019 at 16:04

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