Hybrid roses, such as floribunda, hybrid tea, and climbing roses, are picking up steam and maybe even flowering already in some parts of the country. In colder areas they’re setting buds and getting ready for June blooms. In either case, these heavy feeders will need some supplemental fertilizer to keep them growing strong. For landscape, species, and heirloom roses, usually some compost and a little organic granular fertilizer in spring is enough to keep them healthy. But hybrid roses, which are bred to bloom, need a bit more pampering.
The first step is to do a soil test in your rose garden to see what nutrients may be lacking. Nitrogen deficiency will result in yellowing leaves. Phosphorus deficiency will result in poor root growth, and potassium deficiency will reduce the overall vigor of the plant. Excessive amounts of any of these fertilizers can also cause problems. In addition to compost, add fertilizers that will bring these “big three” nutrients into line.
In general, a fertilizer with a 3-1-2 ratio of nitrogen, phosphorus, and potassium is best. Apply it every three weeks throughout summer to keep your roses blooming into fall. I like an organic fertilizer because it’s slow release, allowing the fertilizer to be taken up by the plants as needed, and doesn’t result in a strong flush of new growth that aphids would love.
Some gardeners have experimented successfully with home remedies for fertilization as well. Sprinkling 1 to 2 cups of dried coffee grounds around the roses results in shinier leaves and better flowering. Roses love the nitrogen and slightly acidic nature of the coffee grounds. Watering your roses with a solution of 1 tablespoon of epsom salts in 1 gallon of water in spring and early summer helps with overall plant vigor, especially if your rose soils are deficient in magnesium. Even a slurry made of ground-up banana peels will give roses an extra shot of potassium.