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They are related
They are related and the confusion began when plant fanciers centuries ago mistook pelargoniums as geraniums. Even though we now know the difference, we still mostly just call them all geraniums because it seems simpler — and in our mild climate we can grow both as perennials.
http://www.mercurynews.com › 2021/11/26 › bay-area-gardening-qa-marigolds-and-geraniums
Bay Area Gardening Q&A: Marigolds and geraniums