A panicle is a cluster of flowers which grows on the end of a branch or shoot. Panicles are a type of flower cluster known as a raceme. Racemes are very common in the natural world, coming in a variety of shapes and sizes. Panicles are perhaps most commonly found on grasses such as rice, oats, and rye. It is helpful to know how to identify a panicle and distinguish between it and other racemes for the purpose of flower identification, since many identification keys assume that people are familiar with the terminology used to describe different kinds of flowers.
Racemes in general are indeterminate inflorescences, which is a fancy way of saying that they are clusters of flowers which are arranged along a stem in a plant which will keep growing until it is prevented from doing so by frost or other events, in contrast with a plant which reaches a certain stage of growth and stops. In the case of a panicle, the growth is made up of a number of small branching stemlets, each of which carries one or more flowers. The panicle is classically loose and open, with each flower having the potential to develop into a fruit or seed if it is fertilized.
Depending on how the flowers of a panicle are arranged, they may bloom from the bottom to the top of the cluster, or from the center to the sides. People can judge how long a panicle has been on the tree by looking to see how many flowers are open. Many panicles will also continue to bloom for several days after they are removed from the parent plant, as long as they are put in water. This trait makes them popular as cut flowers.
In addition to the grasses, other plants which produce panicles include lilacs, yucca, baby's breath, catalpa, hydrangeas, and elders, among others. Some plants produce inflorescences similar to panicles, such as the corymb, a type of raceme in which the stems of lower flowers are longer than those of upper flowers, creating a cluster of flowers with a flat top. Other types of racemes include bracts, spikes, umbels, and catkins.
Panicles are common among plants grown as ornamentals for their flowers. These loose growths of flowers can be very attractive when the plant comes into bloom, and the gradual unfurling of the buds extends the blooming period, ensuring that the plant will stay in bloom for several weeks.