Most of the peony species bloom before the regular cultivars of lactiflora and its' hybrids. By planting some of these it is possible to enjoy a much longer peony season and there are many attractive species amongst them with both interesting foliage and pretty flowers. The bloom dates are usually compared to the widely grown hybrid cultivar Red Charm and the number of days before or after are then used to give an indication of its earliness or lateness. This way seasonal and geographic differences are less important and more observations make the data more reliable. Unfortunately the species are not too widely grown and thus observations of the blooming dates are not too common. There is a 'bloom date project' at the American Peony Society where you can see these dates for many cultivars, including several of the species. However, when it comes to the species, most are based on a single observation, thus reliability is not too high. Next to that, many of the species grown are not true-to-name but so-called garden hybrids, as different species grown together often give hybrid seeds, thus dates given may not always be for the true species. Last, many species are absent from the list, reflecting the fact that many are nearly impossible to get or to grow.