Most native flowers (not just cactus flowers) here are yellow so other colors are most welcome.
From last week here's my Rebutia, a South American cactus.

Rebutia einsteinii
This is a Thelocactus from Mexico, notice it has big tubercles instead of distinct ribs
Thelocactus tulensis.
These cacti are from exotic Oklahoma and Texas.

Echinocereus Reichenbackii
From last week here's my Rebutia, a South American cactus.

Rebutia einsteinii
This is a Thelocactus from Mexico, notice it has big tubercles instead of distinct ribs
Thelocactus tulensis.These cacti are from exotic Oklahoma and Texas.

Echinocereus Reichenbackii
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flowers
Thanks for the pics. Parsing back up. I wonder what causes the needle length difference?
From:
Re: flowers
I don't know the answer, but I know it's not simple. Spines can offer shade to the plant as well as protection from animals, but some cacti don't seem to need them one way or the other.
From:
Re:spines shade etc
I'm working with adaptibility amongst some other thing with the roses.