Wiktionary
n. An expert on the identification and cultivation of plants
WordNet
n. an expert in the science of cultivating plants (fruit or flowers or vegetables or ornamental plants) [syn: horticulturist]
Wikipedia
A plantsman is an enthusiastic and knowledgeable gardener (amateur or professional), nurseryman or nurserywoman. "Plantsman" can refer to a male or female person, though the terms plantswoman, or even plantsperson, are sometimes used.
The word is sometimes said to be synonymous with " horticulturist", but that indicates a professional involvement, whereas "plantsman" reflects an attitude to (and perhaps even an obsession with) plants. A horticulturist may be a plantsman, but a plantsman is not necessarily a horticulturist.
Usage examples of "plantsman".
The gardens had their own plantsmen, a young couple from Potomac who apparently made a very nice living tending gardens around town.