It sounds like a good idea. Id only use it while its the hottest part of the day , and make sure the plant dries before dark. If you play with the distance you might not have to get the plant wet at all. As the water drops evap they absorb energy (heat) so Make sure the drops evap before hitting you plant and you will still get the cooling effect. The wind also has to be blowing the right way if there is any, to make sure the cooled air blows across your plant..