How and When to Fertilize Roses for Vibrant, Beautiful Blooms

Roses are one of the most popular flowers in the world—the fragrant, multi-petaled beauties come in a variety of colors and sizes, making them perfect for just about any garden. Despite their popularity, roses have a reputation for being hard to manage; they're heavy feeders, meaning they require a significant amount of nutrients and frequent fertilization.

Fertilizing roses can promote healthy growth, which improves resistance to diseases and enhances the blooms' beauty. Fertilizer also replenishes essential nutrients in the soil—like nitrogen, phosphorus, and potassium—that may be depleted over time. To ensure you're fulfilling this plant's fertilization needs, we spoke to experts who shared their tips for how and when to fertilize roses.

When to Fertilize Roses

Fertilize roses in early spring as they begin to leaf out, waiting until you see about 6 inches of new growth. Continue to fertilize your roses during the growing season, stopping feeding in late summer or early fall when they begin preparing for winter dormancy. "Fertilizing late in the season may encourage unnecessary tender new growth which may get damaged by cold snaps in the fall," says Jimmy Speas, president of the Winston-Salem Rose Society. "This damaged growth may then be susceptible to further damage by pests."

Nutrients That Roses Need

Roses require several key nutrients, including nitrogen, phosphorus, and potassium. Additionally, they require trace elements such as calcium, magnesium, and iron, among others, says Wes Harvell, rosarian at Jackson & Perkins. "Without these nutrients, roses may have stunted growth, pale or discolored leaves, and decreased flowering," he says.

• Nitrogen: Promotes healthy leaf and stem growth, giving roses a lush and green appearance.
• Phosphorous: Supports the root development and flower and seed production of roses.
• Potassium: Potassium enhances disease resistance, which improves flower quality and increases plant hardiness.
• Calcium: Strengthens strong cell walls and chlorophyll production.
• Magnesium: Like calcium, magnesium also strengthens strong cell walls and chlorophyll production.
• Iron: Helps with photosynthesis and overall plant vitality.
  

How to Fertilize Roses

How you fertilize roses depends on the type you are growing and when they were planted. When applying the fertilizer, follow the instructions on the packaging for guidance on how much to use.

Newly Planted Roses

Wait at least six weeks after planting new roses before fertilizing them to allow time for the roots to establish, says Harvell. Sprinkle a balanced fertilizer specially formulated for roses, such as a 10-10-10. around the base of the plant. After applying, water the plants thoroughly to help the nutrients reach the roots.

Established Roses

Fertilize established roses in early spring as new growth begins and again in late spring or early summer after the first flush of blooms, says Harvell. Scatter a balanced fertilizer specially formulated for roses, such as a 10-10-10, evenly around the drip line (the area under the outermost branches) of the rose bush, says Harvell. Water the plant thoroughly after fertilizing.

Container Roses

Fertilize container roses every four to six weeks during the growing season. "Use a water-soluble fertilizer or a slow-release granular fertilizer formulated for container plants," says Harvell. "Dilute the water-soluble fertilizer according to the instructions on the packaging and water the roses with it. If using a granular fertilizer, sprinkle it on the soil surface and lightly scratch it into the top layer of soil." Water the plant thoroughly after fertilizing.

Best Fertilizer for Roses

A balanced fertilizer specially formulated for roses is ideal, but you should have your soil tested before choosing a product. While a 10-10-10 ratio of nitrogen, phosphorus, and potassium (NPK) is recommended, a soil test will let you know if your soil needs more or less of a required nutrient.

Once you know the appropriate NPK ratio needed for your soil, you can choose a rose fertilizer. The two most common types of fertilizer are liquid fertilizer and slow-release granular fertilizer. Liquid fertilizer is often used in the first year as it is less likely to burn new roots, says Speas. This type of fertilizer is typically applied more often than slow-release.

Organic vs. Non-Organic Fertilizer

Both liquid and granular fertilizers come in organic and non-organic formulas. "Organic fertilizer is from naturally derived sources such as manure, fish emulsion, bone meal, or compost," Smith says. "Inorganic fertilizer is man-made from synthetic chemicals."

Although each one contains the necessary nutrients that roses need to bloom, Speas is a fan of organic options. "Organics feed microorganisms that enable the roses to use the nutrients in the soil for food," he says. This, in turn, enhances the bloom color and reduces the risk of root and leaf burn.