Double Knock Out roses usually do not require any fertilizer to thrive, but only nitrogen-based fertilizers should be used in the spring to promote more greenery. Care for a Knock Out bush with helpful information from a sustainable gardener in this free video on roses.
Hi, this is Yolanda Vanveen, and in this segment we're going to talk about how to fertilize your Knock Out Roses. Now Knock Out Roses are in a great addition to your garden. They're disease-resistant; they're a compact bush rose; they bloom summer through fall and they're just such a joy to have in your garden. And the best part is they really don't need you for anything. So my number one point is you really don't need to fertilize roses if they have really good conditions; they have really good composted, earthy potting soil and they have good drainage. Usually the, most roses will do well without fertilizer. Now the best thing you can do if you want to fertilize is to only use nitrogen based fertilizers when they're growing the greens in the spring; so you want to make sure if it has high nitrogen, you only use that in the spring when they're growing the greens. To get beautiful flowers summer through fall, you want the types of fertilizers that are blooming fertilizer. Any type that are rose blooming fertilizer because they're going to be high in phosphates and phosphates is what makes the blooms. And you never want to fertilize through the winter and the fall with nitrogen 'cause that encourages greenery. So when it freezes hard, it will shock your rose and it won't do very well. So naturally, just let it get on a natural cycle. I don't fertilize any of my roses and they seem to do really well without it. So make sure if you do fertilize; nitrogen in the spring but phosphates in the summer.