Mitochondrial mutation rates vary wildly across the tree of life. Plants typically exhibit some of the very slowest mitochondrial mutation rates, but some angiosperm lineages represent glaring exceptions, with 5000-fold variation in rates observed across this group. I will present the results of our recent efforts to understand the mechanisms responsible for extremely faithful mitochondrial DNA transmission in most plant species, using Arabidopsis as a model, as well as for the recent accelerations that have occurred within other lineages.