The book from Bonnier Publishing's Big Picture Press's Welcome to the Museum series, is a curated guide to plant life, with artwork from Katie Scott, aiming to give readers the experience of a fascinating exhibition.
Willis, who wrote Kew's 2015-20 Science Strategy said at the launch, at Royal Botanic Gardens Kew: "The big problem in this country is that children are not interested in plants."
She said plant science undergraduate numbers were going "down and down and down" and that young people need to be enthused about flora.
Willis cited Peppa Pig, Winnie the Pooh, Triffids, Little Shop of Horrors and Bill and Ben but said: "Plants don't have big eyes and beautiful fur" to appeal to children, adding: "We need to turn that around and interest children in plants early on."
She said the book's "fantastic drawings" and quirky facts could help capture children's imaginations and make them "the next generation of plant scientists".