A diagram showing some kinds of tepal aestivation in flower buds. A: imbricate; B,C: cochleate; D: contorted; E: valvate; F: open.

Aestivation or Estivation, refers to the positional arrangement of the parts of a flower within a flower bud before it has opened. It can be an important taxonomic diagnostic; for example Malvaceae flower buds have valvate sepals, with the exception of the genera Fremonotodendron and Chiranthodendron, which have sometimes been misplaced as a result.

Classes of aestivation include

• cochleate
• contorted or twisted — every tepal is outside its neighbour on one margin, and inside its neighbout on the other margin
• contortiplicate
• crumpled
• decussate
• imbricate — where one tepal is outside all others, one is inside all others, and the others are outside on one margin and inside on the other
• induplicate
• open - tepals do not overlap or even touch each other
• quincuncial
• reduplicate
• valvate — tepals touch without overlapping

Aestivation is also sometimes referred to as praefoliation or prefoliation, but these terms may also mean vernation: the arrangement of leaves within a vegetative bud.

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