My embark has 2 ocean biomes (and 1 land biome, but irrelevant for the question).
I dug out my fort right under the first ocean biome on the same level as the lowest level of the second ocean biome. (first ocean is 1 tile deep, second ocean is 3 tiles deep)
The second ocean biome only exists in a small part of the left bottom corner.
The levels above and below my, dug out, fort (just 1 z-level) are 90-95% aquifer, while my fort level is mostly non-aquifer.
Seemed strange to me to have 1 big non-aquifer layer between aquifer layers, but it's not the question itself.
On my fort level I got a few plants and a mushroom tree growing on the most outer right half. (which might be a coincidence, as I already was using the left half & smoothed most of it)
These plants are still present, although it should be all smoothed out and havent bothered cleaning them up.. Im expecting it is possible to get rid off
On the left bottom side I dug out a tiny part 1 z level lower for my farms and wells.
Muddying/wells weren't a problem by using a simple manual waterpump to desalt the water and a diagonal entry to prevent pressure leaks. (and to keep it thawed during winter)
The strange thing is.. I dug out a bit more later on for my pastures and it doesn't grow any moss (or plants/trees).
The farms/pasture area is 1 z level lower than my fort level and that z-level itself is mostly aquifer (as mentioned above).
The question : Why isn't there any 'wild' growth on my second level?
Every tile, except the farm/pasture tiles themselves, are smoothened to prevent trees blocking off water.
The description on each pasture tile is: "Muddy sandstone Cavern floor" with "A small pile of mud" or something similar.
I got 8 farming plots working at 100% just to the North of the pastures and they should all be under the first ocean biome.
It is worth to mention that my caverns (atleast the first 2 caverns) seems to be randomized a bit badly.
It looks like deep pits with deep passages, but a lot of area's are inaccessible (the ramps are missing or just aren't any)
When I started to build looms (or designate parts of the caverns) my FPS dropped terribly, which I am slowly fixing by opening up each and every cavern area from a central accesspoint.(hopefully that will fix the pathing drag)
There are plants and trees in the caverns (and were already growing in the first level, as mentioned)