just googled that, found one image that looked quite similar so it could be, the strange thing is, i only planted it out about a month a go, i grew it on my spare bedroom windowsill, i didnt plant it there tho, i had a large pot in there growing dahlias last year, then after i removed them and planted them out this and another plant which looks like a strawberry (ill get photos soon) germinated, so i kept watering them, and they survived the winter and now are as the photo shows .... but ive never bought hollyhock seeds lol
only thing i can think is it was in the compost i grew the dahlias in ??