Answer: Osteospermum are tender perennials so most of us in cold climates have to treat them as annuals. The information I found on overwintering sounds very much the same as you would annual geraniums; take the plant inside and either treat as a house plant for the winter or pinch a stem off for rooting and keep the rootings indoors during the winter months. Next spring take them outdoors and sink the pots into the garden so you can enjoy the flowers all summer.
Best wishes with your Osteospermums!
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