Giant puffball

This was a surprise finding in the garden a few weeks ago - a giant puffball (Calvatia gigantea).  I have never seen one here before - they are usually found in meadows, fields and deciduous forests.  It is about 180mm in diameter and appeared in a path beside the pond which was dressed with bark chippings, so I wonder if that is how the spores arrived.  Giant puffballs are good to eat when fresh but my gastronomic advisors, Cherry & John, thought it was past its best by the time I found it so I left it alone.

I have been keeping an eye on it and it has gradually turned brown and the splits in the surface have widened.

Here is how it looks this week - a bit like a mouldy artisan sourdough loaf.

I read that each giant puffball contains about seven trillion spores and that if they all produced mushrooms within two years they would occupy 800 times the volume of the earth.  Fortunately they don't but if one or two do I may be able to try one next year.