I'm a Registered Landscape Architect. Papercutter is totally correct ... depending on some variations from state to state. To get licensed in most states you'll need a degree from an accredited landscape architecture school ( http://www.asla.org/FullListofAccreditedPrograms.aspx
)and usually two years of full time work under the direct supervision of a licensed LA in order to take the license exam ( https://www.clarb.org/Candidates/Pag...moverview.aspx
The degree is much more broad based than planting design. Most 4 year degrees only have two semesters of planting design class, but it is worked into projects that you'd do in three years of design studio classes. It is very diverse from planting design, to site planning, to road and parking design, to large campus planning, to urban planning, and a lot of environmental issues. You'll have to take psychology, sociology, soils, geology. biology. botany, some surveying, grading and drainage, and several art classes as well as normal college English and Math.
Landscape Architecture itself is a very broad field, but most people in it tend to specialize in certain niches where some combination of some of this is applied all the time and other portions maybe not at all.
It is a big commitment of time, effort, and money that may or may not be worth it depending on what it is that you want to do with that education. The apprentice time is also a big time commitment and really hard to get in this economy. Some employers don't pay much when they know you need the apprentice time. Some go further to dump people after a couple of years and replace them with new interns who need the experience more than a bigger paycheck.
I'm a guy who was a landscaper before I got my degree at 35. I wanted to do residential design and that is what I do now. Along the way I have worked in civil engineering offices doing far more commercial and residential civil site plans, subdivisions, and restoration plans than landscape plans for them. The big benefit to me was that I have a much broader depth of knowledge than just doing planting plans which gives me a big advantage on more complicated residential sites than most landscape designers. However, most landscape designs are not that complicated and many experienced self taught landscape designers are equally capable of the job.
The big question for you is what exactly do you see yourself wanting to be doing ten years from now? The next question is how can you gain the necessary experience to make yourself sought after to do that work? Opportunity is sometimes a matter of pure luck and sometimes a matter of a lot of effort and some luck. For me, having the degree opened opportunities for me that I did not have before, but in a different direction than I expected (civil engineering office). That helped me get my LA license which opened other doors. All of those opportunities gave me the ability to gain a lot of experience, network with lots of professionals, and give me am understanding of how everything works and what I could do to be successful on my own. Now other people bring their clients to me. That would not have happened quite the same way if I just took a few adult ed classes on landscape design.
I was a good planting designer before I went to school. I'd go so far to say that I did not gain a lot in planting design while getting my degree because I probably had more experience in actually doing it than the people teaching it. Many people are talented at things like planting design, but the problem is that people who are willing to pay for it don't do so unless they have:
1. complete confidence in you based on your reputation,
2. your ability to communicate your knowledge before you are hired,
3. and a portfolio of built work.
The problem is that all three of those are like the chicken and the egg. How can you get any opportunities without having these three things and how can you get these three things without the opportunities that they open?
You either have to get a little lucky to work somewhere where you can start to do design work or go through all the process of getting a degree and working for others that are doing something similar to what you want to do in order to learn not only how to design, but how the business works, where the work comes from, and how the people you work for get their work.
Designing is the easy part.