Inflorescences

Inflorescence refers to the arrangement of flowers on the flowering shoot of a plant. It encompasses the floral axis and the stalks bearing individual flowers (pedicels) or flowers borne directly on the axis. Inflorescences can be indeterminate, continuing to grow as flowers form from the apex, or determinate, in which the first flower develops at the tip and growth ends early. The pattern of an inflorescence influences pollination, resource allocation, and how conspicuously flowers are displayed to pollinators.

The major types include raceme, spike, panicle, umbel, corymb, capitulum (head), and spadix-type inflorescences. In a raceme, flowers are borne on short pedicels along a simple, unbranched axis. A spike has sessile flowers attached directly to the axis. A panicle is a branched, compound raceme with multiple pedicels. An umbel has all pedicels arising from a common point, producing a round-topped cluster. A corymb is similar but with differing pedicel lengths so the outer flowers are at about the same level. The capitulum, or head, groups many small flowers on a flattened or rounded receptacle, as in sunflowers and dandelions. Spadix inflorescences feature a thick, fleshy axis with tiny flowers, often accompanied by a contrasting bract called a spathe, as in calla lilies and peace lilies.

Inflorescence form is often characteristic of plant groups and can reflect pollination strategies, such as mass displays to attract insects or efficient presentation of fertile flowers. Variation among species provides a useful basis for identification and classification within botany.