Growing peonies from seed can be a rewarding but time-consuming project. Seed propagation is much slower than dividing established plants, which makes division the preferred method of propagation. It typically takes five to seven years for seed-grown peonies to reach flowering size, and the resulting plants will be similar but not identical to the parent plant. Division creates clones of the plant, which ensures each propagule is the same size, color, and form as the original. This is another reason why division is preferred over seed germination. While seed-grown plants require patience, gardeners can be rewarded with unique seedlings that differ from the parent plant and provide years of enjoyment in the landscape.
Understanding Peony Seed Dormancy
Peonies require a double dormancy to fully germinate, a process also referred to as "two-step germination." Many seeds require a dormancy period to initiate root and shoot development. However, peony seeds require specific conditions to produce a radicle, or first root, and a different set of conditions to produce a stem and leaves.
In nature, these two steps may occur in the first fall and winter, or it may take two years, with the first dormancy requirement being met in the growing season following planting, allowing for root growth, and the second dormancy requirement happening in the subsequent winter, allowing for shoots to emerge the following spring. This means depending on the method and timing of seed sowing, peony seeds require one to two years to complete the germination process. Refrigeration and controlled temperatures can shorten this process indoors.
Germination
Fresh seed generally produces the best results. Seeds collected in late summer or early fall before they become black and completely ripe. Plant them as soon as possible to make sure they are not allowed to dry out. Another option is to harvest seeds after they become fully ripe and black. These seeds can be sown indoors over winter or outdoors the following summer.
Outdoor Germination
Outdoor sowing is the simplest method for most home gardeners. Sow seeds in a well-drained nursery bed that receives at least half a day of sunlight and is protected from excessive heat and drying winds. Press seeds into the soil surface to a depth of no more than ½ inch and space them 1 to 2 inches apart. Cover the bed with about 1 inch of wood-based mulch to help maintain even soil moisture.
Fresh seed is best planted immediately after harvest in late summer/early fall. Dry seed should be planted in mid-summer to allow additional time for hydration and dormancy requirements.
For outdoor germination, seeds receive the warm and cold conditions naturally provided by seasonal weather. Some seedlings emerge the first spring after sowing, but others may require an additional year or more. In some cases, seedlings may continue to emerge over a period of up to three years.
Indoor Germination
Indoor germination allows gardeners to control temperature and potentially speed the process, but it requires careful attention to moisture and temperature.
Begin by soaking seeds in water for several days, changing the water regularly. Place the soaked seeds in a sealed plastic bag containing barely moist vermiculite, perlite, or peat moss. Keep the seeds warm, ideally between 70°F and 80°F, for about three months. During this period, inspect the seeds every two weeks and remove any that become soft or moldy.
After the warm treatment, move the seeds to a cool location between 34°F and 50°F for 60 to 90 days. A temperature a little warmer than the typical refrigerator (42°F to 45°F) works particularly well. This cold period overcomes stem and leaf dormancy. Roots begin to grow during this stage, followed by stem and leaf development. Once shoots begin to emerge, pot the seedlings up in a container or outdoor nursery bed in temperatures around 70°F to 75°F.
Caring for Young Seedlings
During their first growing season, peony seedlings often produce only a single leaf. Provide fertile, well-drained soil, consistent moisture, and protection from intense heat and sun. Seedlings grown in containers should be planted in deep pots because of their extensive root systems. Containers can be buried in the garden for a year or two while plants develop before transplanting them to their permanent garden location. Seedlings grown in containers often underperform. The peony seedlings do best when grown in a nursery bed or outdoor garden space and then transplanted from this in-ground location to their permanent garden location once large enough to grow without close care.
Timeline
Peony seedlings grow slowly. Some plants may bloom in their third year, but most flower in the fourth or fifth year, with a few taking even longer. Those germinated indoors may come to blooming size about one year sooner than those sown and germinated outdoors, but that is not always guaranteed.
More Information
- Propagating Herbaceous Peonies from Seed: The American Peony Society
- Transplanting and Dividing Peonies
- Growing Peonies in Iowa
- Growing Garden Peonies (PDF)
- Peony Types and Cultivars for Iowa
- How to Manage Potential Problems Growing Peonies
- Reasons Why Peonies Fail to Bloom
Photo credits: 1: Aaron Steil