The implication for that second meaning being that all the leaves or petals are doing that -- so like a cardboard box where each flap is on top of one neighbor and under the other. In botany, can especially refer to when there is only two leafs so overlapped. This is, obviously, something that happens more in a bud than a flower. Adopted around 1750 from Latin obvolūtus, past participle of obvolvere, to cover by wrapping up (as in a burrito? I have to wonder), from ob-, on/over/against + volvere, to turn/roll (yes, as in Volvo the car).
She overlapped the obvolute dominoes in an circle.