[Bakha]

In your scenario, where all characters would (I assume) be ICly literate and familiar with brand names, I might go with #1.

Of course, I prefer #2, though I don't really like it either, because it indicates what can be found in the bag. I'd prefer, "a green and yellow plastic bag" that you could then look inside and see, "a bag contains: fertilizer."

Or maybe your sdescs can handle restringing to indicate contents, which would be fairly easily achievable and pretty cool. It could get clunky in the restringing if people filled the bags with lots of items:
a green and yellow bag filled with the remains of a dandelion which seems to be missing its root, the remains of a tuft of crabgrass, the remains of a hunk of clover.

Anyway, by handling bags and such via container objects instead of whole objects, it allows more flexibility from a player standpoint. That way if they want to empty the bag and fill it back up with their own organic compost or use it as a weed collector as in the above example, thus reusing the bags, they'd be able to do that (hey you might have some real treehuggers in such a mud. Reduce, reuse, recycle.