In nature they reproduce via seed and propagate by getting top heavy and falling down then growing roots where they lie. Cutting the tops off and planting them vertically is probably the least likely way it will happen in nature. Cutting the top off and planting vertically is THE preferred amateur grower tek and is much quicker at establishing a growing column than the horizontal-ground-contact method. Really, it isn't hard to get the things to root. Think of them as weeds, they really want to grow and as long as there is some dirt and light available they'll kill themselves trying to live. Get a cutting, get some dirt and put them outside as soon as the risk of freezing is gone in your 'hood. The mystery goes away very quickly. J ust don't let the dirt get wet. Wet is the enemy during the rooting phase of its' life Your pic looks very good. You could cover the roots a little better. In fact you could bury the whole column a couple or few more inches deeper and it will grow that many more roots. Big root systems allow for big fast growing columns. You could easily get three columns out of the cactus in the pic. I'd assert you only need a 6 inch cutting to successfully get roots growing.
Edited by pharmer, 19 March 2023 - 02:37 PM.