From Wikipedia:

Horticulture is the art and science of the cultivation of plants. The word horticulture is a 17th century English adaptation of the Latin hortus (garden) and cultura (culture). Horticulture is the art of gardening or plant growing, in contrast to agronomy - the cultivation of field crops such as cereals and animal fodder, forestry - cultivation of trees and products related to them, or agriculture - the practice of farming.

Horticulturists work and conduct research in the fields of plant propagation and cultivation, crop production, plant breeding and genetic engineering, plant biochemistry, and plant physiology. The work particularly involves fruits, berries, nuts, vegetables, flowers, trees, shrubs, and turf. Horticulturalists work to improve crop yield, quality, nutritional value, and resistance to insects, diseases, and environmental stresses.