G'morning arnia,
Would you advise I use any rooting powder (indole-3 b) for the obregonia? I've heard from friends that obregonia is very difficult to root, so is there any extra measures I can take to have it successfully root?
I do not use any rooting powders. The rooting of obregonia is easy.
I use garden-lime as a drying agent which coveres over the cutting face.
The garden-lime is not rooting powder.
Also what medium would be good for obregonia and geohintonia?
I use pumice sand 2~4 mm size for the rooting medium. You can use any permeable material with similar size.
should I lightly moisten the medium like you would with lophophora? Or moisten the bottom of the pot or just leave it dry?
You have to dry the cactus long enough before setting for the rooting. It will be 3 weeks at least.
If you watered from top, water never reaches to the cutting face physically. Please water from bottom.
Frank