Whether you choose the temporary indoor light or garage, and then when you finally move the forest outdoors, it would be best to keep the roots covered.
Not Trident….but I have started Poplar trees indoors under standard fluorescent shop lights, supplemented with natural sunlight and heat from a patio door, during the last weeks of the winter cold. The lights were only during natural daylight hours due to my cloudy days at the end of the winter weeks. Lights were turned off at night. When Spring temperatures leveled in earnest, and a frost was no longer possible, I moved the trees outside. Even though evenings were chilly the tree did well. Trees seem to naturally handle cold spells. The cold spells in the Spring were upper 30s to low 40s. I needed to move them back indoors twice due to frost possibilities. Not a huge work effort really. In the end the trees adapted to my full summer sun quickly.
