Anyone can enjoy a great landscape, but few can create one. Good Landscape Designers need to know all about drafting, architecture, geology, and, of course, horticulture. Of these, horticulture is what lacks most among the majority of even the best Landscape Designers.
It is uber-important to know the personalities of the plants that go into the landscape in order to know how they will behave after the landscape is installed. Many of the best Landscape Designers actually got a degree in horticulture and got into Landscape Design, instead of getting their degree in Landscape Design and just trying to learn about horticulture as they went along.
There is no messing around in Landscape Design. (Only those who install the landscape get to be messy.) Unlike many of the other horticultural industries that are overrun with insufficiently educated people who would have been just as happy with assembly line jobs, Landscape Design actually expects at least some degree of relevant formal education, and hopefully, experience.