Flower Aestivation
Aestivation refers to the way
petals and sepals are arranged and
folded in the expanding flower bud.
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Flower Aestivation
Major types of Aestivation
Imbricate
Vexillary
Open
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Quincuncial
Cochlear
Valvate
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Convolute
Carinal
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Flower Aestivation
Valvate
Valvate aestivation is when petal or sepal margins touch each other, but
do not overlap.
Calotropis
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Flower Aestivation
Valvate
Valvate aestivation in
Hibiscus sepals.
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Valvate aestivation in lilac
(Syringa) petals.
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Flower Aestivation
Open
In open aestivation, the petal or sepal margins do not touch or overlap.
Alliaria
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Flower Aestivation
Imbricate
Imbricate aestivation is when petal or sepal margins overlap in the
unfolding bud. Individual petals may have margins that completely overlap
adjacent petals (external), have no overlapping margins (internal) or have
one external and one internal petal margin (alternating).
Cochlear imbricate aestivation has 1 external, 1 internal and 3 alternating petals.
External
Alternating
External
Internal
Internal
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Alternating
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Flower Aestivation
Imbricate
Quincuncial is a specialized five petal imbricate aestivation with two external
petals (1 & 2), two internal petals (4 & 5), and one alternate petal (3).
External
1
Alternating
Internal
5
4
3
Internal
External
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2
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Flower Aestivation
Imbricate
Convolute imbricate aestivation is where each petal overlaps the adjacent petal.
It is also termed twisted or contorted.
All petals overlap in an
alternating pattern.
Datura
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Flower Aestivation
Imbricate
When a convolute, imbricate aestivation forms a twisted spiral it may
be called a contort aestivation.
Phlox
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Plumeria
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Flower Aestivation
Imbricate
A special form of convolute, imbricate aestivation where the petals are
twisted in a spiral that opens like a fan is called contortiplicate.
Plicate means folded like a fan.
Hibiscus
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Flower Aestivation
Vexillary
Vexillary is the type of aestivation found in the papilionaceous flower form
seen in some legumes. The back petal called the banner or standard (4) is the
largest and is exterior and overlaps the two lateral petals called wings (1, 2),
which in turn cover the two folded front petals collectively called the keel.
Banner
Banner
Wing
Wing
Wing
Yellowwood (Cladrastis)
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Keel
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Keel
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Wisteria
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Flower Aestivation
Carinal
Carinal aestivation is found in non-papilionoid legumes such as redbud (Cercis)
and is similar to vexillary aestivation. In carinal flowers, the banner petal (4) is
the smallest petal, and is now inside the two larger lateral wing petals (1, 2).
The two folded front petals are the keel.
Banner
Wing
Wing
Wing
Keel
Wing
Banner
Keel
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Flower Aestivation
Vexillary vs. Carinal
A comparison of vexillary vs. carinal aestivation.
Large exterior banner
Vexillary
Banner
Wing
Inner
wings
Exterior
wings
Wing
Wing
Keel
Wings inside banner
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Small interior banner
Carinal
Banner
Wing
Keel
Wings exterior to the banner
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