Green House wireing methods. Wet Area I'd say yes.
I;ve been told PVC not a good choice?/
Anyone out there can share info?/
Thanks in advance.

Yoop:

Wet area, yes

IF ambient temp is over 50 C, (122f) then PVC is non-compliant.
Support and subject to physical damage? Sch 80 solves the physical damage.

Can the ambient exceed 122f in MI? On a hot sunny day, inside a glass box??

The few (2) that I have in my Twp are:
One at High School, PVC, 32" AFF to 6 GFI outlets. Fans (2), power roof vent (4) and lighting is IMC, per design professionals spec, and that saved me a plan review rejection letter. Temp last week reached 142f before the maintenance guys turned on the fan circuit and vent circuit that they shut off by mistake. Bless them.

The other is at a wholesale garden supply, it's all RGC, been there a long time. A few 120 GFIs were added in PVC, routed on the exterior wall and LBd in.

Hope this may help.

Greenhouses may be in Gregs domain?

Not a lot of greenhouses here. A screen cage might be as close as you get. For those EMT seems to be better than PVC, just because of the expansion and drooping problem. The install is usually bend up the pipe, paint it to match and install it. Cosmetics may not be an issue if this is a commercial greenhouse. The issue might be direct water spray from irrigation.
RMC might be better but the cost will be prohibitive for most customers

I'd use EMT and raintight compression fittings.