Your Complete Guide to Fertilizing Roses: When to Apply and How

Most roses require consistent fertilization during the growing season to stay healthy and keep blooming. However, not all types of roses need the same nutrients in the same amounts at the same time. Newly planted roses have different fertilizer needs than established roses.

Here is a complete guide that will tell you how and when to fertilize roses.

Nutrients That Roses Need

Below are some common nutrients found in rose fertilizer:

• Nitrogen (N): A macronutrient roses need for foliage growth.
• Phosphorus (P): A macronutrient roses require for root growth. Most rose fertilizers have more phosphorus than any other macronutrient.
• Potassium (K): A macronutrient that is crucial for flower formation.
• Micronutrients: In addition to the aforementioned macronutrients, roses also require micronutrients including iron, calcium, and magnesium.

Differences in Fertilizing Roses

When to fertilize roses and how much fertilizer to use depends on the type and age of the rose and blooming pattern. Repeat-blooming roses need more frequent fertilization and tea roses require more nutrients than shrub roses.

To keep track of when you fertilize your roses, it is helpful to keep records using a calendar or a task reminder app.

How and When to Fertilize New Roses

• When planting, amend the soil of the planting hole with rich organic matter. This will create a nutrient-rich environment for your roses.
• Start fertilizing new roses about one month after planting when they show some growth, which indicates they are getting established.
  
• Gently incorporate a high-phosphorus, slow-release fertilizer as recommended by instructions, combined with a handful or so of bone meal to aid root development.
  
• Continue to fertilize every 3 to 4 weeks as the roses are establishing but only with a mild fertilizer such as fish emulsion.
  

How and When to Fertilize Established Roses

• Fertilize when the first leaves start to appear and there is no more danger of severe spring frosts. After that, the fertilization schedule should be based on how long, and often, the rose is blooming, usually around once to twice per month.
• Fertilize after each bloom cycle, gradually reducing the amount of fertilizer by half each time. Stop fertilizing six to eight weeks before the first average frost date to help prevent the plant from producing large amounts of new soft growth late in the summer, which is vulnerable to cold damage in fall and winter.
• Fertilize the roses once they've gone dormant. Adding fertilizer will not harm the plants at this point but will get them ready for the next spring.

How and When to Fertilize Container Roses

• Mix a slow-release granular rose fertilizer into the potting soil when initially planting your roses in containers. Add bone meal to support of healthy root growth.
• Check regularly on the foliage. If it starts to look chlorotic (yellow leaves), this indicates a nutrient deficiency and the plant needs extra fertilization.
  

Organic vs. Inorganic Rose Fertilizer

There are two basic types of rose fertilizers, organic and inorganic. Most organic fertilizers are naturally released into the soil more slowly and over a longer period than inorganic fertilizers. The exception is inorganic controlled-release fertilizers, which release nutrients over several months depending on soil moisture and temperature.

Organic Rose Fertilizers

Aged or composted manure, worked into the soil about 2 to 3 inches deep, is an excellent NPK fertilizer. (Just always ensure the manure is “aged,” i.e. not fresh. Otherwise, the manure will have a high nitrogen content, causing fertilizer burn in the plants.)

Bone meal adds phosphorus to the soil. Mix it deeply into the soil, not only because it does not enter the soil easily with watering but also to prevent wildlife from being attracted by the smell and digging up the soil. Add a heaping tablespoon per rose plant.

Dried blood meal is also a good source of nitrogen. Apply about a tablespoon around each plant. Too much nitrogen burns the roots so don’t apply more than needed.

If you don’t mind the smell, liquid fish fertilizer or fish emulsion, diluted in water according to the product label, is a fast-release organic source of nitrogen.

Other organic fertilizers include:

• Greensand for potassium and micronutrients
• Rock phosphate for phosphorus, calcium, and micronutrients
• Alfalfa meal as a balanced fertilizer
• Seaweed for nitrogen and phosphate
• Coffee grounds sprinkled at the base of the bush for a nitrogen boost
  

Inorganic Rose Fertilizers

There are special rose plant foods tailored to their higher phosphorus needs. These fertilizers have an N-P-K ratio where the second number is the highest, such as 18-24-16. However, you don’t necessarily need to get a special rose fertilizer. You can also use a general complete fertilizer with a high phosphorus ratio, such as 5-10-5, 4-8-4, or 4-12-4. Another option is to use plant food with fertilizer numbers such as 6-12-6, as this would contain 24 percent total nutrients and 76 percent filler material.

For the amount, follow the directions on the label. The rule of thumb for complete fertilizer is half a cup per plant.

Since inorganic fertilizers are more concentrated than organic fertilizers, don’t pile them up on dry soil, which causes burning. Instead, spread the fertilizer thinly and evenly around the plant and lightly rake it into the damp soil. The best time to apply the fertilizer is before it rains or watering. Keep the fertilizer away from the canes and the graft union, and water the plants well after fertilizing.

The rule of thumb for controlled-release fertilizer is about half a cup per plant unless specified otherwise on the label.

Tips for Fertilizing Roses

• Soil pH affects how roses absorb nutrients, so always test the soil's pH before applying fertilizer.
• Keep to a regular fertilizing schedule.
• Water roses deeply before and after fertilizing to prevent root burn or shock. 
  
• Apply foliar sprays to roses in the morning. 
• Avoid fertilizing your plants in extreme heat.