Perennial

dauerhaft

(continuing without cessation or intermission for several years, or for an undetermined or infinite period — see also perpetual, unceasing)

ganzjährig

(lasting or remaining active throughout the year, or all the time)

mehrjährig

(of a plant: active throughout the year, or having a life cycle of more than two growing seasons)

wiederkehrend

(appearing or recurring again and again — see also recurrent)