The Sarah Mum is a chrysanthemum of such dense, globe-like perfection that it looks less like something that grew from soil and more like something a very dedicated mathematician designed on a Sunday afternoon with nothing else to do. The Canary Yellow Sarah Mum — 4 inches across, one screw, no water — has painted this geometric ambition the precise shade of a bird that has never once in its life had a quiet opinion about anything. It is the loudest object in any room it occupies and it has not objected. Not once. We have checked.