Aestivation = Arrangement of floral parts in bud before opening
| Type | Description | Overlap Pattern | Family/Example |
|---|---|---|---|
| Valvate | Petals/sepals touch at margins, NO overlap | Edge-to-edge | Calotropis corolla, Solanum calyx |
| Twisted (Contorted) | Each petal overlaps the NEXT on ONE side (spiral) | One margin overlaps, other is overlapped | Malvaceae (Hibiscus), Convolvulaceae |
| Imbricate | Irregular overlapping — some overlap others, some are overlapped, no pattern | Irregular | Cassia (Caesalpinioideae), Rosa |
| Vexillary (descending imbricate) | Standard largest/outermost, then wings, then keel innermost — strict butterfly pattern | Specific arrangement | Fabaceae (Papilionaceae) ONLY |
How to Distinguish Imbricate from Vexillary:
- Imbricate = general irregular overlapping
- Vexillary = SPECIFIC ORDER: Standard always outermost and largest; keel always innermost and smallest. The order is fixed: Standard > Wings > Keel (from outside to inside)