I have a Euphorbia grandicornis (Cow's horn) that is extremely root bound. It belonged to my father and I know that it was in the current pot for at least 4 years. I am attempting to re-pot and I am not exactly sure what the best method is. Trim the roots and re-pot all or cut away from main stem that looks dead and re-pot? (I am most bothered but what to do with all of the roots??)

Thanks for any help!
Jen

Hard to get rid of all those roots. Am I correct in the assumption that those roots are mainly attached to the 'dead' main stem?

I am sure these will re-root if you start with the arm cuttings, but it would take time for new root systems to develop which means the arms would sit idle and/or deteriorate...

My approach would be to repot with the roots and see if there is a way of minimizing the appearance of the dead looking main trunk by shortening it to just above the highest alive branch...

Thanks for the advice. It is a unique plant and I want to nurse it back to good health!!

The main stem on these plants sometimes dies back, but the low-down branches will persist... this feature is especially evident in seedlings, where the main stem basically terminates when it branches early on close to ground level. I agree with Thijs' advice. You can restart the arms from cuttings but you may see the same thing happen afterwards to them. This is not a small plant in the ground and it tends to require some space in containers after a few years. I have never tried to trim the roots.