The Peony Fertilizer Guide: Timing and Application Tips

Peonies are a beautiful addition to any garden. These richly symbolic flowers have been enlivening borders and homes for centuries. But, if you want to make the most of their fragrant and colorful blooms, proper fertilization is essential. Read on for all you need to know about fertilizing your peonies.

When Do I Fertilize Peonies? Key Takeaways

Fertilize new plants in spring when new shoots appear and mature plants when flower buds appear. Apply finished compost and bulb fertilizer or a 10-20-20 granular fertilizer. Avoid the crown when applying, or you could damage the plant irreparably. Avoid overfertilizing, especially with nitrogen, as it may inhibit flowering.

Fertilizing and Peony Plant Health

All plants need nutrients to survive – the essential building blocks of any healthy plant. Not only are the nutrients vital, but each nutrient must be provided in the right quantities, or your plants will not flourish and, in extreme cases, may even die.

All peonies may benefit from fertilizing if they show signs of a lack of nutrients. This includes herbaceous peony plants, tree peony, and a peony bush.

Nutrients Explained

Most nutrients are sourced from the soil and organic matter in which the plant grows. Adding appropriate nutrients to your peony soil is critical for plant health, especially for potted peonies where the nutrients in the soil are not replenished naturally.

Plant nutrients are split into primary macronutrients, secondary nutrients, and micronutrients. Don’t be fooled by the names – all groups are essential in plant health.

Macronutrients

The primary macronutrients, so-called because plants require them in the largest quantities, are:

• Nitrogen (N) – promotes leaf growth
• Phosphorus (P) – promotes flowering and fruiting
• Potassium (K) – promotes root growth and aids photosynthesis

The letters N-P-K will be found on most bags of Fertilizer, always in that order. Each nutrient is designated a number, which denotes the percentage of that nutrient found in the bag.

These percentages will guide you to the main focus of the Fertilizer you buy. For example, a 15-30-15 fertilizer will have 15% nitrogen, 30% phosphorous, and 15% potassium, with the remainder comprising secondary or micronutrients and filler materials. This formulation, evident in these values, will be good for general plant health, but mainly flower growth because of the higher phosphorus content.

Secondary Nutrients

Secondary nutrients are still technically classified as macronutrients but are required in smaller quantities than the primary ones. The secondary nutrients are:

• Calcium (Ca)
• Magnesium (Mg)
• Sulfur (S)

Calcium’s primary function is to provide structural support to cell walls. Magnesium benefits photosynthesis, and sulfur is an essential building block of chlorophyll development and protein synthesis.

Micronutrients

There are seven essential micronutrients:

• Boron (B)
• Zinc (Zn)
• Manganese (Mn)
• Iron (Fe)
• Copper (Cu)
• Molybdenum (Mo)
• Chlorine (Cl)

They make up less than 1% of the dry weight of the plant but still play a vital role in health. The easiest way to ensure your soil has sufficient micronutrients is by mixing in organic compost, but specific micronutrient fertilizers are also available if needed.  

Forms of Fertilizer

There are two primary forms of fertilization – organic and inorganic.

Organic fertilizers are made of natural materials such as:

• Deposits of minerals
• Peat moss
• Compost
• Seaweed
• Animal manure

Over the long term, these fertilizers improve soil health and productivity.

Inorganic fertilizers, as the word suggests, are synthetic. They come in 3 different forms:

• Liquid Fertilizer – usually diluted in water and applied while watering your peony plants.
• Powdered Fertilizer – typically sprinkled onto the soil just before watering, but can also be diluted in water.
• Granular Fertiliser -often slow-release products worked into the soil as needed. They allow the nutrients to leach into the soil over a longer period whenever water is applied.

Signs Your Peony Plant is Lacking Nutrients

Identifying nutrient deficiencies in growing Peonies (or any other plant) is difficult because the signs of different deficiencies may look similar. Also, because nutrients work together, a deficiency in one may show the symptoms of a deficiency in another.

But generally, there are some fundamentals to watch out for.

Peonies without sufficient nutrients won’t perform as well and are unlikely to display their trademark peony bloom. If you notice a sudden change in your peony flowering season, lack of nutrients may be the cause.

They are also more susceptible to pest and disease damage when they aren’t in good health. While pests and diseases can attack at any time, regular fertilizing prevents them from settling and taking over your beds.

While lack of fertilizers is an issue, overfertilizing is also a concern.

Overfertilized garden peonies often develop poorly and produce few blooms. Excessive soft leaf growth and a tendency toward disease could also be signs of too much nitrogen. Always follow the instructions on your chosen Fertilizer exactly to avoid overfertilizing.

When and How Often Should You Fertilize a Peony Plant?

There are three Peony plants – herbaceous peonies, Itoh or intersectional, and tree. All types benefit from regular fertilization in early and late spring, summer, and fall – depending on your chosen product.

Fertilize newly planted Peonies at the beginning of spring when the new shoots are about 3 inches high.

If the Peonies in your garden are well established, consider waiting until the flower buds are starting to show before you fertilize them. Fertilizing well-established peonies at this time will better promote flower growth.

After the initial application of fertilizer, apply fertilizer lightly after flowering and again in late August. The plants gather energy before dying back in the fall (for more, see our guide to cutting back peonies) to allow them to pop up again the following spring, so good health at this time is just as crucial as pre-flowering. 

The Best Fertilizer for Peony Plants

The first step to ensuring that you have healthy peonies is to plant them in nutrient-rich soil. This will give them the best start and limit your fertilizers’ reliance on optimal blooming.

As you divide and replant peonies, enrich the soil with compost to boost them. You can also scatter bone meal around the newly divided and replanted peonies to encourage strong root development (note that peony roots can freeze in cold temperatures).

When fertilizing, use a general bulb fertilizer or NPK 10-20-20 fertilizer. An NPK 5-10-10 (lower concentration fertilizer) is great for top-ups when your plants are already performing well.

There are a few commercial products available close to these ratios that are also great for use on other plants:

• Lilly Miller Bulb & Bloom Food
• J R Peters Jacks Classic No.4 Blossom Booster Fertilizer

(Editors Note: Petal Republic participates in partnership programs with Amazon and other merchants to help connect readers with relevant products and services we may recommend).

Keep weeds to a minimum to avoid competition around the roots and maintain the right nutrient levels.

How to Apply Fertilizer

The application will depend on your chosen product. Some fertilizers are spread around the plants and gently dug into the soil, while others are diluted in water and applied to the soil with your regular watering schedule.

Remember that fertilizers come in different concentrations and need to be diluted or added following the instructions exactly. Overfertilizing will burn the roots and leaves and can stunt growth. It’s always better to apply too little than too much.

Always avoid applying the product directly to the crown when composting or fertilizing. Feed the soil around the plants instead, right where the foliage stops.

Key Considerations

Overfertilizing

As mentioned before, too much of a good thing is as much a problem as too little.

Stick to the guidelines on the packaging of the Fertilizer you have bought. Apart from these general guidelines, only apply a particular fertilizer if your plants lack a particular nutrient. This will prevent any imbalances or problems with salt build-ups in the soil.

Using the Incorrect Fertilizer

Avoid using fertilizers high in nitrogen during the peony growing season. These promote excessive soft growth that is vulnerable to disease. Too much nitrogen will also discourage flowering by directing the plant’s energy toward foliage growth.

Fertilizing Peony Plants FAQs:

Wrapping Up

These easy-to-grow plants can become stars in your garden with some basic care, but only if properly placed and fertilized. They are one of the most glamorous of perennial flowers, and the vast array of colors is a welcome addition to any garden. With the right approach, you could have 100-year-old peonies in your garden (if, of course, you last that long).

Further Reading:

For more, see our in-depth peony plant guides to:

• How to Cut Peony Flowers for a Vase or Bouquet
• Peony Light Requirements
• How to Divide Peony Plants
• The best companion plants for peonies in your garden.
• Can Peonies Grow in California?
• Can Peonies Grow in Florida?

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