Great roses begin with good soil. Does your soil have adequate nutrient levels and the proper pH? Find out by taking a soil sample before you plant your roses. Taking a soil sample is as easy as 1-2-3.
Roses require ongoing fertilization to keep them blooming well. All fertilization programs start with a soil test for pH and base fertility. The pH of the soil needs to be between 6.0 and 6.5 for optimal availability of nutrients from the soil. Our soils in the Kansas City area generally have a pH above 7.0. The pH can be lowered with the addition of soil sulfur, ammonium sulfate, or aluminum sulfate.
Our soils generally contain adequate amounts of phosphorus and potassium. Nitrogen is usually needed because rain and irrigation leaches it out of the soil. Roses need 2 to 4 pounds of nitrogen per 1000 square feet of garden every growing season. It should be applied in one pound increments, applied 2-4 times throughout the growing season. Whether using a chemical fertilizer or an organic fertilizer, it should contain a combination of slow release and fast release nitrogen. If you use lawn fertilizer with a formula of around 30-3-3 (30% nitrogen (N), 3 % phosphorus (P), and 3% potassium(K)), two teaspoons of fertilizer spread around the bush and worked into the soil. (Be very sure that the lawn fertilizer doesn’t contain weed killer!) If a balanced formula such as 10-10-10 is used, about 1/8 cup (or 2 tablespoons) of fertilizer is needed for each application. For a fertilizer containing 2 to 5% nitrogen such as manure or alfalfa meal, ¼ cup fertilizer will be needed for each application.
Start fertilizing in April and make the last application no later than the first of August. For large shrub roses, adjust the amounts to no more than twice the portions listed above. Remember that more is not better. Over-fertilized plants attract insect pests and have less resistance to disease.