The lotus is associated with purity, and spiritual enlightenment. The Ganesha idol sitting on a lotus is symbolic of His divine purity and wisdom. Lord Ganapati is known as the destroyer of all obstacles (Vighna- vinashaka). The lotus grows in muddy waters but rises above it untainted and beautiful. It portrays the idea that we humans can rise above all challenges and difficulties in life but maintain inner purity and grace, the way Ganesha does. The lotus flower shows balance and harmony. When Lord Ganesha is seated on a lotus, it means that he governs the balances material and spiritual aspects of life. The lotus fully blooms in the morning and closes at night, meaning the cycle of renewal. This aspect of the lotus can be connected to Ganesha's ability to help his devotees overcome obstacles and start afresh.
Buy the clay Ganesha idol seated on a lotus from GiriUK