Inflorescence is a term to describe the arrangement of flowers, or florets, on the stem of a plant. Single inflorescences involve all the flowers on the plant gathering in a single pattern, whereas compound inflorescences involve complex patterns formed by multiple single patterns of flowers. Inflorescences are divided into two primary categories: racemose, or indefinite, and cymose, or definite.
In corymb inflorescences, the florets are arranged along one main floral peduncle. The stems are of different lengths so that the florets all end at the same level. Corymbs are sometimes referred to as "flat-top racemes."
The florets on umbels all arise from the same point on the peduncle. When multiple umbels gather together, it is called a compound umbel. The secondary umbels in compound umbels arise from the tip of the primary umbel.
Cymes have one main stem that ends in a flower. In biparous cymes, two lateral stems develop just below the flower. In uniparous cymes, a single stem develops. This growth pattern repeats at each flower.
The florets on spike inflorescences are attached directly to the peduncle. Spikes have no stems or branches. Spikelets, which are small spikes, include some sedges and grasses. Spikes have both male (stamen) and female (pistils) florets. Catkins, a similar plant to spikes, differ in that they have only male or female florets. Spadix inflorescences are thick and fleshy spikes surrounded by a funnel-shaped leaf.
In racemes, the florets are attached along a peduncle, and the stems are similar in length. Older florets occur toward the bottom of the plant, with new florets developing toward the top. A panicle is formed when several racemes gather together.
Capitulum / Head
In capitulum (head) inflorescences, the florets do not occur on stems, but instead gather on a platform-shaped peduncle. Sunflowers are an example of capitulum inflorescences.