I work as a landscape foreman
I can speak to this since I have a horticultural background.
1. I'm assuming those college guys are the ones doing most of the heavy lifting and such. There will be a point when lifting will no longer be possible.
2. For the most part, you'll be fine for awhile, albeit a bit more tired than usual. You probably won't have the stamina you had before, for sure. But later, you'll probably have more problems with your back, feet, pulled muscles, etc. Then you'll have to reduce your physical tasks.
3. If you can, time it for a delivery during the "down season" (here that's Nov-Feb) when there's usually not as much work anyway. That way, you will feel less guilty about being out of commission, and won't feel like you're missing as much.
4. If you're nauseated, at least you'll be outside. I always felt way better when I was outside, it actually seemed to help with the nausea...something about the fresh air, I guess.
Some things you can expect:
1. You'll get tired/out of breath a lot faster than before. You'll have to take more breaks than you're used to. You'll have to learn new limits, which isn't easy when you're used to working hard.
2. You'll need to alternate between sitting and standing a lot to stay in the game longer. I found the best combo was a bit of both. Sitting all the time was bad. Standing all the time was bad. It was good to mix it up.
3. You won't be able to lift bags of topsoil, steer manure, 20 gallon pots with plants, etc once you're past a certain point (without putting yourself at risk for injury).
4. Wearing a back brace in the third trimester really helps A LOT! I strongly recommend it.
5. In the third trimester, you'll need to pee constantly. You'll have to plan for that.
6. Riding around in vehicles gets pretty uncomfortable after a certain point, especially things like work trucks.
7. Finding work clothes that still fit in the third trimester will be challenging. The shirts should be fine (just get a bigger size-go a bit baggy), but you'll need maternity pants, and it can be hard to find ones that are heavy duty enough to be work clothes. Uniform catalogs often have things that work. Don't know what you normally wear, but I'm guessing your best bet will be maternity jeans.
8. Don't know if you do anything on ladders like tree work, but if you do, that will be out because your balance gets bad after awhile and it gets scary to be up on a ladder when pregnant.
9. You'll have to be very careful about hydration. Moreso than usual.
10. Sometimes you get pregnancy brain and forget/space out a lot. That sucks in a work situation. Your brain may let you down, and that can be frustrating at times.
11. You will NOT want to be around any of the commonly used chemicals in landscaping/ag. Don't know if your company uses chemicals, but most do, and if so, you'll need to stay away from them! Someone else will have to do this part of the job.
12. Crouching will be out after about the second trimester because you'll have a hard time getting back up. So if you're installing anything like irrigation pipes, borders, etc, that can be tricky.
Don't know if that helps, but for what it's worth, landscaping is probably more compatible with pregnancy than you might think...as long as you aren't doing a ton of lifting, you should be able to do a lot of the other things you are already doing. Being outdoors always made me feel better when I was pregnant, and I actually felt better being active than I did on my days off sitting around the house.
What will be harder, ultimately, is the time AFTER the baby is born. But that's another adventure...
Has anyone else worked a similar, physically-demanding job through part of their pregnancy? Any insight would be appreciated!