Horticulture (Nurseries and Greenhouses) is the science and art of growing (plants) – fruits, vegetables, flowers, and any other cultivar. It also includes plant conservation, landscape restoration, soil management, landscape and garden design, construction, and maintenance, and arboriculture.
In contrast to agriculture, horticulture does not include large-scale crop production or animal husbandry. Horticulturists apply their knowledge, skills, and technologies used to grow intensively produced plants for human food and non-food uses and for personal or social needs. 
Their work involves plant propagation and cultivation with the aim of improving plant growth, yields, quality, nutritional value, and resistance to insects, diseases, and environmental stresses. They work as gardeners, growers, therapists, designers, and technical advisors in the food and non-food sectors of horticulture. Horticulture even refers to the growing of plants in a field or garden.
Source: https://en.wikipedia.org/wiki/Horticulture