Bananas and their peels do contain high levels of potassium, an essential nutrient that roses—and all garden plants—need for everything from stimulating growth to producing flowers. But burying whole peels can backfire. As soil microorganisms work to break down the peels, they extract significant amounts of nitrogen from the soil, which results in less nitrogen for greening up plants. The best place for banana peels is in a compost pile, where they can break down alongside other nutrient-rich table scraps. To give plants the balanced nutrition they need, top-dress with compost instead.