Landscape Architects & Designers plan and design your landscape. They will discuss your vision for your space and help you to create the artwork that becomes your landscaping. They will help you choose plants and materials. In contemporary practice, landscape design bridges between landscape architecture and garden design.
Landscape Contractors install your landscape features, including the softscapes, like soil and vegetation, and hardscapes, like fences, water elements, stones, and walkways.
Landscape Managers focus on improving and maintaining your existing landscape. If you don’t want to take on regular maintenance yourself, you may want to hire a landscape manager. Landscape managers will work with you year round and also provide snow and ice removal.
Horticulturists, sometimes called horticulturalists, are the plant experts. A horticulturist goes one step beyond and knows the science behind different plants, flowers, and greenery. If your plants aren’t growing, your leaves are being eaten by pests, or you live in a particular climate for vegetation, you may want to work with a horticulturist.
Arborists. By definition, an arborist is an individual trained in the art and science of planting, caring for, and maintaining individual trees. They know about fertilization and nutritional needs, as well as bracing, and support for newly planted trees and garden plants.
Reference: http://www.expertise.com/, https://en.wikipedia.org, www.study.org