Biennial
WordNet
adjective
(1) Having a life cycle lasting two seasons
"A biennial life cycle"
"Parsnips and carrots are biennial plants often grown as annuals"
(2) Occurring every second year
"They met at biennial conventions"
noun
(3) A plant having a life cycle that normally takes two seasons from germination to death to complete; flowering biennials usually bloom and fruit in the second season