I knew the meaning of term 'green thumb' from my favorite manga, Les Mille Fleurs by Nami Akimoto. In the last chapter of book 1, Chika is so sad after Shu, her neighbor and also her secret crush moves to football school to pursuit his dream. Then Chika decides to chin up and focus on gardening, her own dream. Her father sees her and says that she has a green thumb, which means she has natural talent of taking care plants. Later on the same day, Asakura (the handsome yet misterious boy that she ended with hehehe) says the same thing about Chika's talent ;)

Les Mille Fleurs is my favorite manga ever! It made me try gardening, knew a lot of flowers and their meanings (my favorite is Lavender!) and learn Francais (yeah, the title means 'A Thousand Flowers'). I  also always wondering if I have the same thumb, the green one. Well, I'm sure these spinach seed and time will tell me ;)