Inflorescence

A flower is a flower, unless it is a bunch of flowers growing on the same stem, then it’s an inflorescence.

Yarrow

Anatomy of an inflorescence

A singular flower appears at the end of a stem, called a peduncle, nestled in a (normally) green cup, called the receptacle, and surrounded by modified leaves, called sepals. When there are multiple stems or branching stems (rachis), or flowers that occur on a disk, it is an inflorescence. The stalks of individual flowers within an inflorescence are called pedicels. These flowers are called florets, and their leaves are called bracts.

Parts of a flower (USDA)

Types of inflorescences

Inflorescences can be determinate or indeterminate. The oldest flowers of a determinate (cymose) inflorescence are found at the end of the stem, as other flowers bloom in succession, down the stem, with the youngest flowers at the base. Indeterminate inflorescences are just the opposite, with older flowers at the base and younger flowers occurring closer to the tip.

There are six major types of inflorescences:

• raceme - elongated axis with stalked flowers; indeterminate (cherry, radish, currants, some mustards)
• spike - elongated axis with stalkless (sessile) flowers; indeterminate (bottlebrush)
• cyme - broad, flat-topped or slightly domed arrangement, with flower clusters in groups of threes and attached to a disk; determinate (sunflowers)
• corymb - flat-topped or dome-shaped arrangement of unbranched florets; indeterminate (yarrow)
• panicle - a branched raceme; indeterminate (yucca)
• umbel - similar to a corymb, but branches emerge from a single point; indeterminate (carrot, ginseng, dill)

Mustard inflorescence

There are also catkins (mulberry), spadix (cobra plant), and many subdivisions of each category, but this is a good start.

When an inflorescence produces fruit, such as sunflower seeds, it is called an infructescence.

Now you know.