Several variables...

Free ozone blown though the greenhouse at high concentration will burn the plants.
Almost instantly - I've done this before, came back into the greenhouse and all the plants were literally brown and shrivelled after just 15 minutes.

Generally what is done is that the ozonator is used on the inlet of the air circulation/filtration system and/or on the inlet to the exhaust fan {this also kills the moss and alga on the outside of the building}.

When ozonating the the water to the plants this increases the fertilizer utilization and kills the scum and 'pests' that may develop. Also, makes it a little easier to use organic fertilizer in an indoor situation. The other benefit of this is that it can also increase the germination succes and seedling growth - particularly of obstinate tree varieties... Tweet