Stems do root if you bury them, i sometimes bury the 1st two nodes so i can cut them away rooted at a later date.
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For rooting on the plant...5-6 days after the above post i had reason to do some air layering, while I had the necessary items i done the plant that's recovering (after being lost in the post) it's then going to be a mother and a plant for flowering.
I wrapped a piece of wire around the stem and tightened it enough to restrict the sap but not to cut it off.
Above the choke i removed the 1st nodes, put root it sponges in the ball then closed it around the stem.
11 days later it's (the stem) rooted.
Eta... I'll let it grow a reasonable amount of root before cutting it away, there's no point in cutting it off for it to go back the way.