1) Biological process 2) Biology terminology 3) Organic process 
In botany, perennation is ability of organisms, particularly plants, to survive from one germinating season to another, especially under unfavourable conditions such as drought or winter. It typically involves development of a perennating organ, which stores enough nutrients to sustain the organism during the unfavourable season, and develops into...
Survival of a plant for a number of years. ... To live over from season to season. ... (09 Oct 1997) ... 
[n] - the process of living through a number of years (as a perennial plant)
noun the process of living through a number of years (as a perennial plant)