the mode of arrangement of sepals or petals in a floral bud with respect to other members of the same whorl is known as aestivation. When the margins overlap but not in any particular direction, it is called imbricate aestivation, commonly found in plants like Cassia and Gulmohar. In contrast, valvate involves no overlapping, twisted involves overlapping in a specific direction, and vexillary is a specialized arrangement found in papilionaceous flowers like peas.