Well, how is growing in soil with bacteria, fungi, nematodes, protozoa and micro-arhtopods 'dirty'? So any produce grown outdoors is dirty? Setting aside that plenty of people grow orgnanically indoors, of course..
I think growing with those things is dirty because they are in dirt. I don't mean anything bad by "dirty" -- I just mean "involving dirt". The produce itself is not dirty - just the method by which it was grown. I grow in organic soil and live on an organic farm, so I do truly understand organics and soil life. I am also a Master Gardener in my state, which I think is a decent background in horticulture from which my POV comes.
When I talk about plants growing on rocks, I don't mean lichens necessarily, but they are in the short list of pioneer flora. I am talking about the concept of "primary succession" or "soil formation"
At the beginning, there was no soil. All that is present at the beginning of primary succession is mineral material; sand, volcanic ash, lava, bare rock, etc. Soil contains organic material (living bacteria, fungi, plant roots, animals, etc. and the dead and decomposing parts of these creatures). In primary succession the initial organic matter is added to the mineral substrate by the pioneer plants. Pioneer plants become established on the bare mineral substrate from spores, seeds, or other propagules that are blown, washed, or caried in by animals.
There are lots of pioneer plants out there that can pop out of bare mineral substrates like lava.
Other examples of non-soil substrates and their companion plants:
Barren rock- blue-green bacteria (cyanobacteria), lichen
Barren sand- lyme grass, sea couch grass, marram grass
Salt Water- green algae, marine eel grass, pickleweed
Fresh water- algae, mosses, freshwater eel grass
These things came around before soil and helped crack it up into smaller particles in which the bacteria and fungi eventually grew.
I have a great appreciation for organics and a great appreciation for hydroponics.
I wish people would chill on their personal agendas and look at how these systems are similar.
tommy