Aestivation (botany)

Aestivation or estivation refers to 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.

The terms used to describe aestivation are the same as those used to describe leaf vernation. Classes of aestivation include:

Lilac (Syringa vulgaris), valvate aestivation

Phlox (Phlox paniculata), contorted aestivation

Vinca minor, contorted aestivation

Ipomoea, contortiplicate aestivation

The corolla of Merremia tuberosa was contortiplicate in the bud

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