Tek for Blue Myrtle cuttings?

I have a nice chunk of Myrtillocactus sp. It isn't M. geometrizans, it is very heavily spined, spines are an ashy gray colour and feel woody, they are flat/angular. WIll post a pic soon.

I have currently got it sitting in a course sand & perlite mix, have herad this genus can be slow to strike? Any tips for promoting root growth, or speeding up root formation. I have never propagated any of this genus and thought it was about time I did as they are very attractive to my eye.

Obviously, you've got to let the cutting callus over properly before planting it out.

However, beyond that I'd say your potting mix sounds about right. I prefer to use ordinary cacti mix to strike my cuttings, but that's purely because perlite annoys the hell out of me - a decent breeze, and the stuff just blows all over the shop. I've heard of people getting excellent results from striking difficult cuttings into a hydroponic medium called "seramis". I don't know much about it, but quite a few people seem to swear by it.

Otherwise, in my experience I find that an external heat source warming the pots speeds up root formation very rapidly, particularly as we come into winter. I use a flat pad heater that I picked up from the local hydroponics and homebrew shop. This is also a good piece of kit to have as it's also very useful for getting seeds to germinate, and should you have any delicate plants that don't like the cold... plus you can use to heat a fermenter up for beer production, but that's another story.

all my M. geo cuttings are left unpotted until they form root buds. these guys like long days and warm temps. all my winter cuts take 2-3 months, where as my summer cuts take 2-3 weeks.