Original article by David Graper, former SDSU Extension Horticulture Specialist and Master Gardener Program Coordinator. Reviewed and updated by Kristine Lang, Assistant Professor and SDSU Extension Consumer Horticulture Specialist.
Peonies (Paeonia sp.) are one of the most-common flowers growing in many people’s gardens, and for good reason. There are few plants that are as durable, easy to grow and long-lived as a peony.
Keep reading to learn more about this early-summer blooming plant that thrives in South Dakota!
Types of Peonies
Most gardeners in South Dakota are used to the herbaceous peonies, which originated from the Chinese Peony (Paeonia lactiflora) and the common peony (P. officinalis). There are hundreds of different cultivars available that were developed from these original two species. Some gardeners may have also discovered the woody or “tree peonies.” These were mostly derived from P. suffruticosa. These plants offer the largest flowers and a new range of colors that include yellows and other flower colors. However, tree peonies are generally not as hardy, so will need to be planted in a protected site or mulched over the winter. Unlike the herbaceous types, these plants develop woody stems that should persist and continue to grow from one year to the next, allowing the plant to get larger each year.
Flowers
Peonies are prized for their large, showy and fragrant flowers, which come in a wide variety of colors including white, pink, red, purple, burgundy, peach and multi-colored types. The flower form may be classified as single, Japanese, anemone, semi-double, double or bomb. Peony flowers may range from about three to eight inches wide, depending on the species and cultivar. Flowering time varies from early June to early July.
Site Requirements
Peonies grow best in a site that receives full sun exposure. Some peonies may do okay in partial shade, but might not produce as many blooms as those planted in full sun. The plants prefer a well-drained soil, but they will tolerate clay soils too. Peonies do best when they are watered regularly, especially in the spring when they are growing vigorously and forming blooms. Avoid using high amounts of nitrogen fertilizer, as this can decrease the number of flowers that a peony will produce.
Planting and Dividing
Peonies are available in the spring, usually as potted plants in garden centers or as bare root plants in the fall. September to early-October is considered the best time of year for planting and dividing existing plants. Keep in mind that if you are tackling an old, well-established plant that the tuberous roots can be quite large, two to four inches in diameter and up to 12 inches long. You will need a heavy spade or shovel to dig one up but be careful to not damage the roots. They may be large but tend to be quite brittle.
Try taking out a section, like a piece of pie, from a large plant so that you will have less chance of causing major damage to the original plant. Each division should have several buds or eyes, which will be quite evident in the fall of the year, usually found one to two inches below the soil surface. These buds should be positioned at about the same depth in their new location when planted. The “eyes” on the roots should be no deeper than two inches when covered with soil. Planting the roots too deeply is a common, but avoidable mistake. Cut off the stems about six inches above the soil line to make it easier to handle and to reduce water stress on the division after planting. New foliage will develop next spring from the buds on each division.
Common Issues
Weak Stems
One of the biggest issues with growing peonies is that the flower heads become quite heavy as the flowers develop. Heavy rain and thunderstorms of early summer can soak flower heads, causing the peony stems to collapse from the weight of the flower. This can be prevented by placing some support for the flower stems in place in the spring, just as the new shoots are beginning to grow. The most-effective method is to use a piece of woven wire or even a piece of cattle panel, suspended about a foot above the ground by surrounding stakes. You can also purchase round mesh supports from garden centers and online outlets.
Cost
Some gardeners might be surprised at the cost of a peony plant, especially for some types, like the fern-leaf peony, which can cost $20 to $50 for a single plant. But remember that a peony is an investment in your garden that will pay dividends for many years to come. Peonies are also a fun plant to share among friends and can become a plant that is handed down for generations.
Not Flowering
Over the years you may notice that your peony is producing less blooms than previous seasons. There are several reasons for poor bloom production on peonies, such as:
- Peony roots are buried more than two inches deep.
- The peony clump is old and larger.
- Too much nitrogen has been used.
- The site is too shaded.
- Buds have been damaged by frost, disease or insects.
If your peony planting is new or you’ve recently divided your plants, ensure you give the new plants a few seasons to establish and produce blooms. Pay attention to the depth of the roots, especially after you’ve divided a planting. Peonies should be divided every three to ten years, especially if you notice a reduction in flowering. If you see buds that appear discolored or have holes, you will want to explore if you have a disease or insect that is impacting your blooms.
