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Aestivation or estivation is the positional arrangement of the parts of a flower within a flower bud before it has opened. 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.

Aestivation can be an important taxonomic diagnostic; for example Malvaceae flower buds have valvate sepals, with the exception of the genera Fremontodendron and Chiranthodendron, which have sometimes been misplaced as a result.

• Terminology

• References

The terms used to describe aestivation are the same as those used to describe leaf vernation.cite-ref-1[1]

Classes of aestivation include:

• crumpled

• decussate

• imbricate – overlapping

• contorted or twisted – every petal or sepal is outside its neighbour on one margin, and inside its neighbour on the other margin.

• cochleate – spirally twisted.

• contortiplicate – contorted and also plicate.

• quincuncial – with five parts, where two petals or sepals are outside all others, two are inside all others, and the fifth is outside on one margin and inside on the other.

• induplicate – folded inwards.

• open – petals or sepals do not overlap or even touch each other .

• reduplicate – folded outwards.

• valvate – margins of adjacent petals or sepals touch each other without overlapping.

• vexillary – a special type of aestivation occurring in plants like pea; in this type of aestivation a large petal called standard encloses two smaller petals.

cite-note-11. ↑ citerefhickey-m-king-c-2001Hickey, M.; King, C. (2001). The Cambridge Illustrated Glossary of Botanical Terms. Cambridge: Cambridge University Press.