Persistence (botany)



Persistence is the retention of plant organs, such as flowers, seeds, or leaves, after their normal function has been completed, in contrast with the shedding of deciduous organs after their purpose has been fulfilled. Absence or presence of persistent plant organs can be a helpful clue in plant identification, and may be one of many types of anatomical details noted in the species descriptions or dichotomous keys of plant identification guides. Many species of woody plants with persistent fruit provide an important food source for birds and other wildlife in winter.

The terms persistent and deciduous are not used in a consistent manner by botanists. Related terms such as long-persistent, generally deciduous, and caducous suggest that some plant parts are more persistent than others. However, these terms lack clear definitions.

Species with persistent parts
There are numerous herbaceous and woody plant species that produce persistent parts such as bud scales, sepals, fronds, fruits, seeds, strobili (cones) or styles. Note that the trait of persistence exhibited by a given species within a genus may not be exhibited by all species within the genus. For example, the Equisetum genus includes some species that have persistent strobili while other species have deciduous strobili.

Common witch-hazel (Hamamelis virginiana) may have a persistent calyx or a persistent fruit (or both at the same time). After flowering in the fall, the sepals (calyx) and pollinated ovary persist during the winter months. After the ovary is fertilized in the spring, it fuses with the calyx to form a greenish fruit, which eventually becomes woody and brown. In the fall, the ripe fruit suddenly splits, explosively dispersing black seeds up to 10 m. The empty capsule persists after the seeds are dispersed.