To study landscape architecture, you need to learn how to draft, how to understand and organize spaces, how to do planting design, how to identify plants, and understand horticulture and history of landscape architecture.
There are two major career paths for you in landscape architecture: practice as a landscape architect or to teach in colleges or universities. The earlier that you decide which path you are going to take, the more likely that you'll be successful at an early age. Some famous and well-respected landscape architects have combined the two paths successfully. They teach at the universities and have their own landscape architectural practice. Even as a college or university professor, people respect you more if you have actual working experience and have some built projects. If you only teach in colleges or universities but have no actual working experience and have no built projects, people will consider you as a "paper" landscape architect and they are not likely to take you seriously, because they'll think you probably do not know how to put an actual project together.
In many states in the U.S., if you want to practice landscape architecture, you need to obtain an architect's license or a landscape architect's license. A landscape architect's license requires a combination of passing scores on the Landscape Architectural Registration Exam and a number of years (usually 8 years) of education and/or qualified working experience, including a minimum number of years (usually two years) of working experience in the U.S. Your working experience needs to be under the supervision of a licensed architect to be counted as qualified working experience for your architect's license. You need to contact your state's landscape architectural licensing board for specific licensing requirements for your state.
If you want to teach in colleges or universities, you probably want to obtain a Master Degree or a Ph.D. It is not very common for people in the landscape architectural field to have a Ph.D. One reason is that there are few Ph.D. programs for landscape architecture. Another reason is that landscape architecture is considered a profession and requires a license. Many people think an architect's or a landscape architect's license is more important than a Ph.D. degree, since you need to have an architect's or a landscape architect's license to practice landscape architecture. You cannot call yourself a landscape architect if you do not have a landscape architect's license, even if you have a Ph.D. in Landscape Architecture. You'll be punished if you violate these rules.
To become a tenure professor, you need to have a certain number of publications and pass the evaluation for the tenure position. Publications are very important for tenure track positions. Some people say for the tenure track positions in the universities and colleges, it is "publish or perish."
American Society of Landscape Architects (ASLA) is the national organizations for the architectural profession. Membership is voluntary. There are different levels of ASLA membership. Only people with a degree in Landscape Architecture or with a landscape architect license can be (full) AIA members. If you are a landscape architectural student, you can join as an Associate ASLA member. Contact ASLA for detail information.
Gang Chen, AIA, LEED AP BD+C, Author of "LEED GA Exam Guide," "Architectural Practice Simplified," "Planting Design Illustrated," and other books on various LEED exams, architecture, and landscape architecture