Is this variety of Osteospermum a perennial or an annual?

They are perennials and the hardiest of all the Osteospermum. If they like it in your garden, they will spread. You don't need to prune them, only cut off some of the rooted pieces if they spread too far. You can transplant these rooted pieces, of course. I try to keep on top of dead-heading mine, but never succeed!

I haven't managed to find any other Osteospermum that have made it through the winter. I also bought 6 new supposedly hardy varieties this spring and the summer wet rotted the roots!

All of my Osteospermum are 2 and 3 years old..They survived the snow we had this winter and the cold...And I find that if you dont cut them back they will get leggy so I train them to hang over the edges of troughs and raised flower beds and they look really good this way...