Euphorbia milli.
We have had this plant for nearly 50 years.
Since it is quite unwieldy in its pot I haven't repotted it for years but give it some fertiliser in the spring and autumn.
Last year I realised that I hadn't a second, younger plant so stuck three branches in a pot.
I think I might have left the cuttings a few days for the cut end to dry first.
These are looking healthy, one even flowering right now.
The photo is from last year when I thought I would make a photo journal of the few flowers on our balcony, then forgot to up date it.