What can you do with a degree in horticulture ?   Let's see.

You just built a new house.  Looks barren with only soil around it.  You call a Landscape Designer to draw a landscape plan for your residence.   In turn, the plan is given to a Landscape Contractor to install the design.  The plants are bought from a Garden Center.  The Garden Center got the plants from a Wholesale Plant Nursery .  A Plant Propagator started the plants from cuttings, and a Chemical Technician treated them for disease and the Irrigation Technician kept them watered.   All the flowers are purchased from a local Greenhouse Grower who specializes in annuals and perennials.

At the same time, the Wholesale Plant Nursery owner was entertaining clients at a golf course, cared for by a Golf Course Superintendent, and later took them the local Botanical Gardens and Plantation, cared for by the Grounds Superintendent , and that evening they went to a Riverdogs baseball game, cared for by the Athletic Field Superintendent.  Meanwhile, the owner's secretary made sure the Florist had the flower arrangement arrive on time to give to the clients.  On the way, the florist noticed an Arborist climbing a tree to prune out dead limbs. 

Finally, the Landscape Contractor arrives with the plants and installs the landscaping.   He subcontracts the irrigation system to an Irrigation Contractor.   After that, a Landscape Maintenance company cares for your landscape by mowing, fertilizing, and pruning.