Good afternoon, These seedlings are just 8 weeks old. I potted these up to 3 " pots today. I started them in a mix of 2 parts potting soil and 1 part grit. The roots were slowing the flow of water through the pot, so I potted up and used my all grit mix. The grit mix allows great air flow, won't breakdown, and less transplant shock when repotting or potting up. With the grit mix I fertilize with ever watering.
BTW the one in the center has a caudex of 7/8" in diameter.
Thanks for looking, Joe