Tulasi(Basil plant) is considered a medicinal herb and works as an ailment for many physical and mental concerns. According to mythology, it is believed that if a leaf of Tulasi plant along with water of the Holy Ganga River is given to any person at the time of death, they will surely get salvation (Moksha). Tulasi being such a sacred herbal plant is never offered to Lord Ganesha. Any guesses as to why?
Some of them might be aware of this story and some might not be. So let’s take some time off to read this love story. Tulasi is now a plant; back then it was Goddess Vrinda. She, the daughter of Dharmaraja, was a very attractive maiden. One fine day, Lord Ganesha was deeply engaged in meditation. Tulasi was walking along the banks of River Ganga where Lord Ganesha was meditating. Ganesha had a unique charm and felt all the more attractive because of the halo due to meditation. Tulasi just fell in love with Lord Ganesha and told him the same. She told him that she was also doing prayers everyday to find her a very nice man and wanted to get married to Lord Ganesha. Ganesha was then a bachelor because he was in mediation and wanted to search for things in himself before getting into any kind of relationship. So Ganesha rejected her proposal and also told her that. After his meditation, he would get married to someone like his mother, Goddess Parvati.
Dejected by this, Tulasi felt heart-broken and took it as an insult. She then cursed Ganesha that he would get married against his wish. Lord Ganesha got infuriated and cursed her back in return that she will get married to a demon. After this curse, Tulasi regretted the entire conversation and asked for forgiveness. Lord Ganesha was pleased with her being sorry but could not take back his word. He instead blessed her that she would become a very supreme medicinal plant and will be used for all kinds of worships except mine. After this, Lord Ganesha left in peace.
This is the story which we might be aware of. This is why Tulasi leaves are not offered for Lord Ganesha.