If I were doing such a setup, I'd say yes, put the outflow from the print washer into the garden. But before placing a print into the washer, do a quick dunk into a pre-rinse tray filled with water. It will take most of the chemicals from the surface of the print and the washer will deal with just trace amount. At that point all the chemicals - beneficial or harmful - will be diluted sufficiently to not affect the plants one way or the other. However, it's just my barely educated opinion, please take it as such.