Copying Gia's title after finding these forums and reading through her post with interest since I have been having similar thoughts.
I have been in the landscape industry for 25 years. I worked for a landscaper right out of high school for a few summers while attending college. That landscaper was also my college professor. I am a couple classes short of a 4 year degree in Horticulture.
After college I worked for a large wholesale nursery/commercial landscape/garden center for 16 years first as a salesman progressing to sales manager and then making the switch to Container Nursery Production Manager.
I left that company while they were experiencing some financial difficulty and have been working the past 7 years as the right hand man for a Lawn/Snow/Landscape contractor that takes care of a lot of town home associations. I oversee much of the landscaping side of the business as well as doing the lawn fertilization and pesticide applications.
So I have significant hands on plant material experience/knowledge. I have come to realize that my body wont be able to keep up with type of work that I am doing now for the long term.
I have always had an interest in the design aspect doing small projects here and there over the years and I am good with computers.
Located in Minnesota, and I would probably have to go to school part-time while continuing to work.
Well, no easy answers. I only lurked on the last example of this question as the other posts were not only in depth from personal experience but because I don't actively want to discourage anyone. On the other hand (as I've written in private to others) some food for thought:
I honestly don't see enough vigor in the economy yet to sweep in everyone who is on the sidelines in LA, which I think is because most starting and mid career independent LAs have to compete for work vs. an elite realm of people with "connections," or else market themselves vigorously. Overall, to get a chance to do anything really exciting or challenging, you have to get a seat in a large multi-disciplinary firm. Then again, there was a contributor here that had "made it" quite handsomely in a few years of a solo career. Every generality has exceptions.
I don't know what I'd tell the British lady to do instead but she's may be overly optimistic to think that LA somehow is desperate enough for new workers that she can breeze in from a side maneuver like a masters degree. If the software has gotten too expensive or overwhelming in the field where she has experience, I think she would be better off looking into helping design firms improve websites with animation in their online portfolios, etc. At least she's ahead on that even if it would take some adjustments. Your question is a little different with the horticultural and construction experience already in place.
So this is a main point that you probably have run into anyway....there is a characteristic of landscape architecture & construction unlike painting on a canvas when the inspiration hits, or playing in a band who makes music for whoever will listen. It's more like making movies in that you must have both a CLIENT and RESOURCES to support your work becoming reality vs. mental exercise...and sometimes even if you think the first is tied down, you face later client loss of passion to follow through. Then to top if off, there can be just plain withering of funds or other priorities take over and sideline the project.
If you think you have the stamina to face all of that, well go for it. The big surprise losses happen in a lot of other kinds of fields also....whole buildings that never go up when land deals fall through, bakeries and bookshops and malls that close from traffic re-routing, locally produced textiles that get walloped by cheap imports, etc. Even Maya Lin designs have failed or never left the drawing stage. And what you say is true about the body limits (why my husband left horticulture for getting CNC machinist training), so there is that as well. I'm sure other members will offer other insights.
Thanks for the thoughtful reply.
I guess my attraction to LA is that it is something that I can do into my senior years that also utilizes the experience of my career up to this point.
So even if it takes a little time to get there, it will be something that I am passionate enough about to continue for many years, and I will be better off than I am at the point that my body can't take the rigors of the landscape construction end of things.
So, I just typed a response and realize it might be a harsh dose of reality. Don't let it dissuade you, but take it under advisement for what it's worth...
With your experience and background, why not finish that horticulture degree and be a horticultural consultant to landscape architects and urban designers? There are many LA's and entire design studios that haven't the slightest clue about appropriate planting, maintenance, or seasonality (which is, contrary to popular belief, perfectly acceptable). Have you considered teaching horticulture at a university or community college? You could probably do that with a degree backing you. Without a degree, there many find work as horticultural/landscape quality inspectors on larger construction sites representing the client, designer, or contractor. You could enter those fields at a valuable level quickly and likely find professional satisfaction without the back pains.
One thing you said "I would probably have to go to school part-time while continuing to work" will present the greatest challenge. That might work the first year or two, but if you are admitted to a quality program, you can pretty much forget about working years 3-4+. Being a student of landscape architecture is essentially like having two full time jobs in the last few years of school. Few who do not treat it that way ever succeed in the profession. A few of the guys I went to school with who had families and jobs had the passion and skill, but lacked the time. It showed in their projects and resulted in less than stellar entry into the profession. None of them remain involved in "design" and either handle technical issues within firms or have left the profession entirely because they couldn't find satisfaction.
I say all of this as someone who has worked for firms of varying sizes (me, two, five, 300+, and 900+ staff). I have gone from CAD monkey, to landscape architect, to business owner, government employee, and as chief of a landscape department. I also graduated after turning 30 and know the juggling routine that involved. If your "interest in design" is actually a passion and you have completed piles of designs for all kinds of problems (landscape or otherwise) over the years because of that passion, I think this will be a natural progression. If it is just a notion in your head, you might want to take some art classes at a community college and attend some design lectures at the local university and see if you want to continue. It's a commitment that requires continual effort long after you leave the university. Hope this was helpful.