When should you hire a Landscape Architect?

SOMETIMES YOU MUST HIRE ONE,
because their participation on a design team for a public or semi-public project is mandated by a town or city.
For most projects, however, there is one good answer. “When the services of a landscape architect will ensure demonstrably better results.” Of course, that's probably true for any project!
A landscape architect should be included when surface water might collect. Or when slopes are present. Or when a client wants new vegetation or specimen plantings. Or where anything will be built into the ground (like retaining walls, outdoor steps, cabanas, pergolas, arbors, fences, etc.).
A related question
to “When should you hire a landscape architect?” is almost equally important. “When should a landscape architect start on your project?”
Landscape architects are trained to see the big picture. They are educated to understand not just an entire property and its unique or special characteristics, but the cultural and physical context in which a property sits. What considerations lie behind decisions for your property? Does privacy enter in? Views to certain vistas as you enter or pass through a property? Does it make sense to locate a new dwelling near the front, middle, rear, or side of a property? What might the future uses include (such as a wedding, reunion, special events, or maybe a need for an in-law apartment)?

Detail of a Use Diagram for the Bristol Community College Master Plan in my office c. 2009
This sort of planning suggests the landscape architect should be brought in before anyone else. Their first task might be to establish a Master Plan for a property. Even if it’s sketchy at first and without building dimensions or solid decisions like that, a master plan can help tremendously to avoid lost opportunities. Or worse, you'll likely avoid rebuilding or moving an improvement to accommodate some overlooked necessity.
If nothing else, the landscape architect will first provide a global view of a project and its context.
A good landscape architect will work closely with other professionals. Like a building architect and surveyor and civil engineer. But working first with someone trained to see the whole picture is important for a project of any size.
In the past hundred years,
professions like engineering, building architects, landscape architects, and others have become specialized. These days, you would never hire a building architect or a structural or civil engineer to design an attractive retaining wall. One that reflects the natural terrain and adheres to a particular format or aesthetic for the site design. That’s not their bailiwick. Nor would you hire a garden designer or landscaper to design anything technical on an important project.

Mulberry Plantation, Loutrel Winslow Briggs, Moncks Corner, SC c. 1915 Photo Charles Birnbaum 2008
Who relies on landscape architects? Smart homeowners, building architects, property managers, institutions, commercial developers, and municipal and state agencies do. Most hire landscape architects without question for the specialized skills to increase property values and to reduce the risk of problems now and later.