Hard for me to generalize on the U. reniformis 'Big Sister' flower timing. Until this year, I would have said the flower stalks emerged a month or so after the leaves emerged (flowering sometime from June till October). It just seems to happen at random times. However, this year the plant is putting up a flower stalk just as the leaves are beginning to emerge from dormancy. Notice the flower stalk (which so far is over 30 inches tall) is coming from a stolon that emerged from a bottom drain hole. The dead leaves are from last summer.