Theres this guy in the Pereskiopsis Grafting Group on facebook who swears that by grafting to old 'brown' pereskiopsis stems, like ones that have supported a scion for 8+ months, the new graft will be semi-permanent and the graft union wont tend to eventually fail.
I've only ever grafted to tender new growth and I've only seen people graft to tender new growth.
Has anyone grafted directly to an old woody stem? What was the outcome?
I find a single claim on facebook dubious but if there is even a chance it could let a pereskiopsis graft stay good for 2+ years it'd be worth a few trials.