Have you ever successfully grown a plant or had a flower bloom and you got happy out of nowhere well that's the happy chemical serotonin. Serotonin is a chemical in the brain which helps you regulate anxiety, happiness, and mood. low levels of Serotonin can cause depression, well high doses of Serotonin can cause excitement and joy. Growing plants can boost serotonin levels because you feel proud of something you Nurtured and grew. if you have an outside guarding the Sun and digging in the soil can increase serotonin levels and also exercise of being outside gardening Can boost serotonin levels. Having a pop of Green in your home or just a feeling of something alive other than yourself can make you happy. Also having house plants can make you feel more connected with Mother Earth.