If you've ever looked up tips and tricks for growing beautiful roses, you've probably seen advice to use kitchen leftovers like coffee grounds and banana peels as fertilizer. The answer depends on two things: what type of nutrients your roses require, and what nutrients your soil is missing. So, how do coffee grounds and banana peels actually stack up against these needs? Coffee grounds don't provide a significant amount of nutrients, but they do provide a little bit of the basics. Banana peels, on the other hand, have lower ratios of nitrogen and phosphorus, but they are potassium bombs.