Round-lobed hepatica appears to bloom over a couple weeks time, with flowers coming and going according to the weather. Rainy, overcast and cooler weather hold back their blossoming.
Like a lot of flowers hepatica blossoms close up at night, too. This daily opening and closing of blooms is probably related to changes in temperature. Springtime evenings are cool and even cold, so perhaps there is some advantage to the plant in keeping the reproductive parts warm by closing up their petals.
The colorful “petals” of hepatica close up around the stamens overnight. The photo above was taken at 11 am and shows the blossoms just opening up in the daylight. Note that the three rounded bracts are visible.
Close-up photo of morning hepatica blooms taken 1 April 2010. The same hepatica flowers at about 6 pm the previous day were fully open (photo below taken 31 March 2010).