Plants that flower once in their lifetime are known as
monoecious
dioecious
polycarpic
monocarpic

Monocarpic

Explanation:

A monocarpic plant can live years before flowering. Flowering does not by itself result in the death of the plant, but the production of fruits and seeds causes changes in it that will lead to death. These changes are induced by hormones that divert resources from the roots and leaves to the production of fruits and seeds.    

An example of this type of plants is Agave. This plant once it produces its fruit dies.

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