Gardening IS an inherited tendency, but it needn't come from parents or grandparents. It can come from total strangers.
My parents loved to garden. I love to garden, too, and I've met the most interesting and amazing people while gardening, including children.
One summer I noticed a disheveled little boy who would ride by my house on a rusty old bike, slow down just a little, and watch me out of the corner of his eye. Eventually, he stopped to watch and we chatted a bit.
Gradually, he began helping me weed and water. He asked me the names of plants and, when I would tell him, he would whisper them under his breath three or four times. By the end of that summer, he knew every plant in my yard by heart. I gave him my used gardening magazines and a few beginner's books in exchange for his help. He was so surprised and treated them as though they were gilt edged.
One day I tried to give him a small potted plant to take home. "No, thanks," he said. "Nothin' grows in our apartment." So I began paying him a little for helping me garden and, as he grew older and could help with bigger tasks, I paid him more.
I encouraged him to take horticulture classes in high school. Later, I found out that those classes were the only reason he stayed in school and didn't drop out. When he was going through those tough high school years, trying to avoid gangs and deal with some serious family problems, he would sometimes seem angry and frustrated when he came by to weed or mow. He didn't always share what was on his mind, but he was always calmer and happier when he left. His teacher and I helped him get into a local agricultural college after high school.
I'd like to end this happily, but I can't. I've not seen this young man for many years. But I like to think that, wherever he is, his thumbs are green, he has dirt under his fingernails, and his heart is at peace with the world and his place in it.