The absorbed energy is converted to heat energy. The scenario you mention with the LED is very close to the blackbody problem known as the ultraviolet catastrophe.. There is a Wikipedia article about it here. What happens in the situation you described is that the light proof box gets hotter.
Diagnosing rust on geraniums can be a challenge for growers. Rust begins with yellow spots on the underside of the leaves and can rapidly progress with brown fungal spores called pustules in the center of each spot. The pustules are raised up off the leaf surface and feel rough to the touch.
water early in the day to allow leaves and flowers to dry before nightfall. Geraniums like to be well fed, so you should fertilize them with an all purpose 10-10-10 liquid plant food. every 2-3 weeks when they actively growing. Remove the flowers promptly as they fade, or the bloom production will decline.ater early in the day to allow leaves and flowers to dry before nightfall. Geraniums like to be well fed, so you should fertilize them with an all purpose 10-10-10 liquid plant food. every 2-3 weeks when they actively growing. Remove the flowers promptly as they fade, or the bloom production will decline.