Tenango del Valle?

This plant also shows up at a garden center fairly regularly. Can't find much about it, other than one thread in a forum that
said it was an old name referred to duoformis. Looks right in Pilbeam, but I have never seen one labelled duoformis.

thanks Mike

Hi Mike,
Yes, sp Tenango del Valle is a form of duoformis. It come from Tenango del Valle which is in the state of Mexico, I believe. This is rather further north than duoformis is usually found, being Puebla and Oaxaca mainly. But it is known from Morelos, and therefore a spread further north west into Mexico state is not unreasonable.
I picked up what is supposed to be a white flowered form at a cactus meeting last year, but it hasn't yet flowered for me, but its a little early for them to flower here in the UK.

I found this white flowered form of "Tenango del Valle" last weekend
a little bit "blow out of proportions"

M. duoformis in my greenhouse: