In Calotropis, aestivation is

Calotropis has valvate aestivation. When sepals or petals in a whorl just touch one another at the margin, without overlapping, it is said to be valvate.
(2) In pea and bean flowers, there are five petals, the largest (standard) overlaps the two lateral petals (wings) which in turn overlap the two smallest anterior petals (keel); this type of aestivation is known as vexillary or papillionaceous.
(3) If the margins of sepals or petals overlap one another but not in any particular direction as in Cassia and gulmohur, the aestivation is called imbricate. 
(4) If one margin of the appendage overlaps that of the next one and so on, as in China rose, lady’s finger and cotton, it is called twisted.