I have been doing some gardening for several years. I think that the most useful accessory that I have are the LED Grow Lights that I use for the plants that I have indoors. At school, we have all studied how plants can make their own food. When the light coming from the sun hits the plants, there is a chemical within them that can react directly to the light and start a process which will generate the food used up by the plant, so one of the key components here is the light.
If a plant does not get as much as it needs then its growth might be delayed. That is one of the biggest concerns that I have for the plants that I have indoors. That is why I use grow lights on them. Since the new ones that I got were made from LED they can consume lesser energy and can last much longer than older types of growing lights.