We just moved in a new place where lots of Osteospermum are growing on a slope. It probably has been a while since they last cut it and it gets really thick and woody. Gray stems can be seen anywhere and some longer stems are more than 8 ft long!

I'm looking for a way to prune them (cut them back). I read online that you can mow them? That's probably hard since the slope is almost 45 degree and some stems are really thick (half inch). Or should I just remove them and plant something new altogether?

Any suggestion is appreciated!