Bob this is all i know about the two.. berteroniana is larger than alpestris for which it is sometimes mistaken. The leaves of berteroniana are covered in white scurf, making them look gray-green in color. The flowers are more dense than alpestris and their color is green

Thanks hdd,that was helpful.
Bob

But, I realized that both could not be grown here, in hot Bangkok City !
I think I killed them two times and gonna be happen again
with some seedlings that I got from a german friend.

Hi all,
Since posting on 3/17,I now have both plants,and the photos of same.
The P.alpestris is the larger,and is a gray color,and the smaller is P.berteroniana,a light green color.There is likely a difference in the age of the plants here.
The shape of the leaves and spines are pretty much the same,making a true ID difficult until the plants bloom.
Any other info/insight out there on these two from our 'spiny' friends would be appreciated.The fcbs does'nt have much on these.
Bob
P.alpestris
{{gwi:450014}}
P.berteroniana [below]
{{gwi:452530}}