zweilappige

Zweilappige is a botanical descriptor used in Dutch to indicate that a flower possesses a bilabiate, or two-lipped, corolla. The two lips, usually an upper and a lower lip, are formed by the petals and give the flower a characteristic two-lobed profile. This corolla form is common in many flowering plants, particularly within the mint family and related groups in the order Lamiales.

Morphology: The corolla tube often narrows into two functional lips; the upper lip is frequently hood-like, the lower lip three-lobed, and sometimes the lips are of unequal length. The bilabiate structure can influence pollinator interactions by providing a landing platform or guiding nectar access, and in some species it also contributes to a degree of floral self-compatibility control.

Distribution and occurrence: Zweilappige flowers are widespread across temperate and subtropical regions, with many examples in the Lamiaceae (mint family) such as Salvia, Mentha, Lamium, and Ocimum. Similar bilabiate corollas occur in other families that were historically grouped with or near the Verbenaceae or Plantaginaceae.

Taxonomic use: The term is used as a morphological character in keys and descriptions to aid identification. It describes flower shape rather than indicating a taxonomic grouping, and species may vary in lip size, position, and fusion.

Etymology: The Dutch adjective zweilappige literally denotes 'two-lipped,' reflecting the two distinct petals forming the upper and lower lips.

See also bilabiate flowers, Lamiaceae, Lamiales.