From Longman Dictionary of Contemporary Englishhave green fingershave green fingersBritish English, have a green thumb American EnglishGOOD AT to be good at making plants grow → green
Examples from the Corpus
have green fingers• The flower show season is upon us, and whether you have a green thumb or not, you should take a look at your garden.• You really do have green fingers.• He had green fingers, my grandfather. He could grow anything.• Tonight these dames were going to have greener fingers than Percy Thrower. 