apetalous

Apetalous is a botanical term used to describe flowers that lack petals. The word derives from the Greek a- meaning not, and petalon meaning petal. In apetalous flowers the perianth is reduced or absent; if present, the calyx may be the sole envelope around the reproductive structures. The term is used to describe both complete absence of petals and extreme reduction where only vestigial structures remain.

Apetalous flowers are common in lineages with wind pollination and in many grasses, where the flowers are typically inconspicuous and lack petal coloration or shape. Some trees and shrubs also bear apetalous flowers in their catkins or unisexual inflorescences, such as willows (Salix) and birches (Betula), where pollen dispersal relies on wind rather than insects. In other cases, apetalous flowers may occur only in particular flower types within a species, such as male or female flowers in dioecious plants.

Ecology and evolution: the absence or reduction of petals reduces energy spent on petal production and can align with wind-pollination strategies or other non-visually attracting pollination modes. The apetalous condition illustrates floral diversity and adaptation across plant groups. In botanical descriptions, apetalous is often contrasted with eupetalous, meaning fully petaled.