Fertilizing peonies for sturdier stems and better blooms

Peonies are long-lived perennials that produce gorgeous blooms and dark green, deer-resistant foliage. No matter which types of peonies you grow, properly fertilizing peonies has many benefits. In this article, I’ll discuss all the ins and outs of feeding peony plants, including the best products, timing, and techniques to use to get the job done right.

The benefits of fertilizing peonies

Providing the proper balance of nutrients to your peony plants has many benefits. Yes, peonies are tough plants, but without proper nutrition, you could have floppy stems, weak plants, and reduced flower production. Plants that have adequate nutrition, on the other hand, produce thicker, sturdier stems and more flower buds. Their leaves are a dark, lustrous green (instead of a pale, soft green).

Properly fertilizing peonies also results in healthier plants that are more resistant to drought and less prone to fungal diseases like botrytis (gray mold) and powdery mildew. Fertilizing can also help keep the soil’s pH in the proper target range for peonies (6.5 to 7).

Whether you grow common garden peonies (Paeonia lactiflora), woodland peonies (Paeonia japonica), tree peonies (Paeonia suffruticosa) or one of the many other species, hybrids, and cultivars available on the market, the tips on fertilizing peonies found in this article apply.

Start with compost

As is the case for most perennial garden plants, the best source of nutrition for your peonies is the organic matter in the soil around their roots. As the soil microbes process the organic matter, they release a broad array of plant nutrients into the soil for plant use. Add a one-inch-thick layer of compost to your garden beds each season and it will not only add organic matter and improve soil structure, it will also provide nutrients to your peony plants.

Some gardeners even use compost as a mulch to help reduce weeds around perennials and other plants. Do not apply compost (or any other mulch) directly on top of your peony plants or snug up against the young stems. Instead, sprinkle the compost around the new shoots or make a “donut” of compost around the crown of the plant. This helps prevent the crown rot that can settle in when mulch is piled on top of plants.

In addition to compost, you should also feed your plants with a granular fertilizer. Let’s discuss that next.

When is the best time for fertilizing peonies

There are two ideal times for fertilizing peonies with a granular fertilizer.

1. In the early spring, when the new growth of the emerging peony stems is about 12-16 inches (30-40 cm) tall. Feeding peonies at this time supports the current year’s growth, enhances hardiness and resilience, and improves root growth.

   

2. The second time to fertilize peonies is immediately after the flowers fade. Fertilizing at this point in the growing season supports healthy foliage that provides carbohydrates to the roots throughout the rest of the growing season. These carbohydrates encourage the production of “eyes” on the thick peony roots and can result in more blooms the following growing season.

While some gardeners fertilize at both of these times, I find that one feeding per year – at either of these times – is more than adequate, especially if you use a slow-release fertilizer that provides nutrients for a long period of time (more on these in a bit).

For me, fertilizing at the earlier time – when the new shoots are 12-16 inches tall – is easier to do, since the ground is very exposed and it’s easy to see where you’re applying the fertilizer. However, these young shoots are more prone to fertilizer burn than the established stems are later in the season. This is not to say that one time is significantly better than the other (there’s only a few weeks difference between them after all); I’m merely trying to stress that there are pros and cons to both times. Choose which suits you and your garden best.

The best peony fertilizers

While adding compost to garden beds is always a great idea, you should also consider adding a granular peony fertilizer on a yearly basis. Peony fertilizer should contain all three macronutrients (nitrogen, phosphorus, and potassium) in the right balance (see the next section for a discussion of NPK ratios), along with a hearty supply of trace elements and minerals, including calcium and magnesium to help strengthen the stems.

Some gardeners opt to use a bulb fertilizer, but I find that a slow-release granular organic fertilizer does a better job. I like to use a general perennial fertilizer, like Flower-Tone or Jobe’s Organics Annuals & Perennials. Fertilizing peonies with perennial fertilizers such as these or others that are OMRI (Organic Materials Review Institute) certified, is a great organic option if you want to keep synthetic chemical fertilizers out of your garden.

Water-soluble fertilizer options, such as liquid kelp or a general all-purpose liquid fertilizer, are another possible choice. These products are mixed with irrigation water and applied to the plants on a more frequent basis. But liquid fertilizers need to be applied more frequently as they are available for only a short period of time. I find them to be more useful for annual plants than for perennials like peonies. The best fertilizer for peonies is a slower-release granular fertilizer that feeds for weeks, instead of for days.

What NPK ratio is optimum for peonies?

Now that you know a granular product is best for fertilizing peonies, it’s time to look at the best NPK ratio for the job. If you’ve read our article on Fertilizer Numbers and what they mean, you already know that nitrogen (N) is responsible for generating green, leafy growth; phosphorous (P) helps promote healthy flowers and root production; and potassium (K) helps with overall plant vigor. So, what does all this mean when it comes to fertilizing peonies?

The ideal NPK ratios for peony fertilizers contain slightly less N than P and K. We want the fertilizer to support good root and bloom growth, not necessary a lot of foliage. If you apply too much nitrogen to your peony plants, you can end up with thin, floppy stems and few blooms. Look for fertilizers with NPK ratios of 3-4-5, 3-5-5, 2-5-4, or something similar. Low numbers are good because they typically signify organic sources of fertilizers that release their nutrients slowly over time. High numbers can sometimes burn foliage, especially tender emerging peony shoots.

How much to apply when fertilizing peonies

While it does somewhat depend on the brand of fertilizer, in general, herbaceous peonies should receive around ¼ cup of granular organic peony fertilizer per year. Tree peonies can be fed up to ½ cup. If the plant is under 2 years old, 2 tablespoons will suffice.

If you’re ever questioning how much fertilizer to add to peony plants, always err on the side of less. Applying too much can result in fertilizer burn on the stems or roots, excessive top growth at the expense of flowers, and is also a waste of time and money.

How to apply fertilizer to the plants

Slow release fertilizers are applied by sprinkling them in a circle around the crown of the plant. Keep the granules 3 to 4 inches away from the base of the peony stems to prevent foliage or stem burn. Loosely distribute the granules across the soil surface, then scratch them in to a depth of 1 to 2 inches using a cultivator or trowel.

Watch this video to see how I fertilize my peony plants:

Is bone meal a good food for peonies?

If you’re looking for a type of fertilizer that can add a boost of nutrition at the end of the growing season, bone meal does the job. Bone meal is a source of phosphorous which, as mentioned earlier, helps promote strong roots and flowers. Bone meal takes a few weeks to a few months to release its phosphorus (it needs to be processed by soil microbes first), so feeding in the fall means that by the time spring arrives, the added phosphorus is available for plant use. However, many soils already have plenty of phosphorous present and adding more phosphorous can even be harmful. Before adding bone meal to your peony plants, I encourage you to take a soil test to see how much phosphorous is already present in your soil.

Should you add fertilizer when planting peony plants?

That being said, bone meal is a great choice to add to new peony plants at planting time to encourage strong root development in the first few years of growth. There is little risk of it burning the new roots when it is mixed into the soil at planting time. ¼ cup per plant is all you’ll need.

What not to do when fertilizing peonies

A few additional thoughts to keep in mind when fertilizing peonies:

• Too much nitrogen is not good. Select your peony fertilizer carefully. Avoid fertilizers with a high amount of nitrogen.
• Moisture is needed for the nutrients in organic fertilizers to become available to your peonies. Be sure to water after application and then keep the plant watered during times of drought.
• Avoid using manure on peonies. It is generally too high in nitrogen and can cause thin stems and fewer blooms.
• Deadhead the spent flowers (or harvest the blooms and enjoy them indoors before they fade). Removing the dead blooms prevents the plant from setting seed which requires a lot of energy. Most gardeners would rather encourage their plants to put energy toward growing bigger and better roots for more blooms next season.

Peony power

Peonies are a beautiful addition to just about any garden. They are beloved by gardeners the world over, and for good reason. They are low care, lovely, and with a little TLC, they can live for generations.

For more on caring for the perennials in your garden, please visit the following articles:

• When to cut back iris plants
• When to trim hostas
• Fertilizing azaleas
• Caring for hydrangeas in the fall
• When to cut back peonies

Pin this article to your Garden Care board for future reference.