Refers to a person who cultivates plants, often with a nuance of skill or specialization. More specific than a general farmer; implies expertise in growing particular crops.
He is a famous rose grower.
There are many fruit growers in this region.
生産者 is a broader term for any producer, including agricultural products, but 栽培家 specifically highlights the act of growing plants.
Compound of 栽培 (cultivation) and 家 (person, specialist). A straightforward modern formation.