I have left osteospermum in the ground over winter. The stems have grown quite thick.do I prune back quite hard or leave to grow again
Certified GKH Gardening Expert
These are annuals, and will only grow once, flower, and die. It will seed the area though. What comes up the next season will be fresh from seed.
You can cut down the area fully after the plant dies, before the new seeds sprout. Here is an article for more information on the plant: https://www.gardeningknowhow.com/ornamental/flowers/african-daisy/african-daisies-osteospermum.htm