Tree peonies are usually propagated by grafting while herbaceous and Itoh peonies are usually propagated by root division. New peonies come from seed.
Peonies do not come true from seed (the only exception being large populations of species peonies that are isolated from other peonies) so each seedling is something new.
If you wish to multiply one of your prized herbaceous peonies your only real option is to divide it, or graft it if it is a tree peony.
If you are looking to create new varieties of peonies you will need to germinate seeds to find out what has been created.
The techniques below are the ones I use on my own peonies.
Crown division is the technique most used to propagate herbaceous and Itoh peonies. It should be done only in the early fall. The technique is as follows:
- In late August, early September cut down foliage of peony to be divided.
- If ground is very dry, water the plant the day before dividing.
- Dig plant up with a strong spade, taking as much of the root system as possible and being careful not to damage the crown.
- Wash soil from roots with a strong jet of water.
- Leave cleaned root system in the shade for several hours to soften it (this makes it less brittle and gives you more precision when cutting).
- Examine the plant carefully and plan your cuts.
- Each division must have at least one visible crown bud to grow. It is best however to have at least 3 buds per division.
- With a clean, strong knife and working on a rough work bench, make your first cut through the top of the crown being careful to cut down toward the work bench and away from yourself.
- If the plant has long tuberous roots it may make the process easier if the roots are trimmed back to between 6-8 inches from the crown.
- Continue to divide the plant until you have the desired number of divisions.
The new divisions can be stored in peat moss filled bags for several days as long as they are not subject to large swings in temperature.
The new divisions should be planted out in a suitable location, ensuring that the crown buds are no more than 2 inches below ground. See page on How to Grow for detailed planting instructions.
Many desirable peonies are infertile meaning that they do not produce pollen or seeds. Many of the large double peonies fit this class. However if these large flower buds are removed the peony will often produce small single flowers which can often produce pollen and seeds.
Growing new plants from seeds is the only way a peony breeder can develop new varieties and it’s also an interesting challenge.
The popular cultivars of yesterday and today do not come true from seed.
Germinating peony seeds (herbaceous or tree) is a must for anyone interested in breeding peonies. It can also be a rather interesting exercise because of the double dormancy of peony seed.
- Collect the seeds as soon as the pods begin to open (The harder the outer shell, the longer the first dormancy period).
- Place them in a sealed plastic bag with some barely moist vermiculite or soil-less germination mix.
- Place the sealed bags in a warm area of the house (not in the sun) and check them every week to see if the root has emerged and ensure they are still moist (but not wet!).
- Leave them in the warmth until the roots appear. This can take anywhere from a few weeks to several months.
- Once the roots appear and are about 2.5 cm or 1 inch in length, move the bag to a cool location. The temperature should be around 40 degrees F. (I put them in an old refrigerator in my basement.)
- Leave them in the cold for about 10-12 weeks.
- Check them regularly to see if the shoot has appeared.
- If it has, remove them immediately and pot them up in a soil less germination mix.
- Otherwise, after 12 weeks remove the partially germinated seeds and pot them as above.
- Depending on the time of year, you may have to grow them under lights for a few months before being able to transfer outside.
- Keep them under strong grow lights and keep them moist but not soggy. Over watering will kill the seedlings.
- Transfer them outside slowly as you would any other tender seedling They should however be outside in a seed bed by late summer.
Be prepared to wait several years, perhaps 5 or more, before seeing any flowers The first flowers are not always indicative of a plant’s potential. It may well be 7 years before a mature, stable flower is obtained.
Seeds can also be sown directly in the ground where natural temperature cycles provide the conditions for dormancy and growth. When sown directly it is possible to wait until the second spring before the shoot appears. This is brought about by a mature seed with a hard seed coat not having enough time in the fall to overcome the first dormancy and send out a root.
The seed hence sits in the soil until the following spring, which brings the warm moist conditions required to break the first dormancy. As the summer draws to a close a root will be produced. The seed over winters again to overcome the second dormancy before producing a shoot the following spring.
This is by far the most used method today to propagate tree peonies. It is not particularly difficult but takes a bit of practice to get right. Essentially a small sections of tree peony branch is grafted onto a section of herbaceous peony root. The herbaceous root serves as a nurse root until the tree peony produces its own root system.
The Canadian Peony Society offers a video that describes in detail the techniques used to graft tree peonies.