Orchid Inflorescence

Orchids flower in various ways. Even within the same genus, different species have different ways to arrange flowers in inflorescences, which are indeterminate and sometimes reduced to a single flower, terminal or axillary.

Most orchids have inflorescences with two or more flowers, which usually arise from a more or less floral axis comprising an elongated stem and a piece called a peduncle bearing flowers, called rachis.

In most species the flowers are arranged in an erect and elongated cluster, with the flowers arranged in a loose spiral around the spine (for example, Cymbidium). In these, clusters of individual flowers are linked to the floral axis through a short stem called a pedicel.

It may be that the flowers are articulated with the rachis directly without the pedicel, and in that case, the inflorescence is called a spike, as shown in the genres Neuwiedia and Perystilus.

A group of orchids belonging to the genus Bulbophyllum, flowering quite spectacularly, present the rachis so contracted that all the flowers seem to leave the same point as in an umbel. Finally, some other orchids (Oncidium, Renanthera) have branched inflorescences that are named panicules.