Controlled Germination Of Peony Seeds Indoors by Don Hollingsworth
American Peony Society Bulletin No. 214. June, 1975. (pp 27-30).
A peony seed germinates in response to the same sequence of environmental conditions whether it is out of doors where nature has full sway, or is kept indoors in contrived conditions. In either case the minimum requirements of a particular seed must be met or it will fail. Each peony seed has its own individual variations, among which may be its inherent germination timing. This may present an advantage in nature by increasing the probability that at least some of the seedlings are ready to grow at the best time in the spring. For the same reason however, others may not be sufficiently ready and are then lost.
The germination pattern of most peony species conforms to the same general sequence so that most viable seeds can be successfully germinated indoors through the use of one general procedure. Enough is now known about what must be done that an informed and attentive handler may proceed with a great deal of confidence.
Several specific benefits make indoor germination an attractive choice:
- A larger percentage of seedlings can be brought into growth the spring following harvest, perhaps all viable seeds in most instances.
- A greater percentage of surviving plants can be developed from some seed lots.
- In hybrid crosses which use PAEONIA LACTIFLORA as seed parent there are numerous varieties to choose among. Some varieties will produce better germinating seeds from a particular pollinator than do others. The early germination process permits the hybridist to observe these results and plan appropriate adjustments prior to the next pollinating season.
- Every peony grower may gain the satisfaction of knowing first hand how the germination process operates and become able to use this knowledge from which to provide instruction to others who may be intrigued with the possibility of creating new varieties.
As with any technique, practice sharpens the skill of the operator. Peony growers who have not already learned the process will probably enjoy a trial experience with it. The necessary materials are easily acquired. I use polyethylene plastic sandwich bags or small freezer bags, the paper-covered wire ties that come with the bags, and tags which are home cut from salvaged food packages. Lately, I have purchased Twist-Tags, a one-piece combination tie and tag. I now use horticultural grade vermiculite (Terra-Lite), exclusively, for keeping the seeds moist in the bags. In addition, I have access to a salvaged household refrigerator that still refrigerates, which is a great help, making it possible to simulate the winter period any time of the year.
Collect each pod of seeds when the dark color of the maturing seed coats has developed, but preferably before the natural moisture has dried from them. In Missouri, this stage will be reached during mid-July to September, depending on the species involved. Drought will hasten ripening; humid weather will retard it.
2. Cleaning and watersoak period:
Put the seeds to soak immediately in tap water and wash them clean. I usually allow them to soak for several days, especially if they had become dry, but the water should be changed daily so that it does not become foul. Remove any “mushy” or rotting seeds as their condition becomes evident.
3. Packaging to retain moisture:
Any time after the seeds have become fully plump and are no longer taking up water, they should be transferred to a plastic bag containing a small amount of moistened sterile medium, such as horticultural grade vermiculite. Avoid prepared potting mixes that contain added fertilizer nutrients. It may be desirable to disinfect seeds before bagging by dipping them for several minutes in a solution made of one part Chlorox in nine parts water.
Tightly close the seed bag to preserve moisture, using a paper-covered wire closure that is durably made so that it will survive repeated openings. Attach a tag on which may be written the identification of the seed lot and inspection notes as germination progresses.
4. Incubation period:
Place the bags of moist seeds in a warm area, preferably not less than 75 degrees Fahrenheit. Holding the seeds moist at this temperature will permit the necessary internal changes to go forward, yet permit the control of the date at which root development gets underway. If held in the 60’s (degrees F.), the internal changes will still go forward but many seeds will initiate root growth at random times, confronting the handler with the necessity of repeated transfers of the rooted seeds to the cold period. Place a thermometer with the seed bags and read it regularly to be sure that the chosen area remains warm enough. I find the garage to be satisfactory during hot weather. Later, when outside temperatures are cooler, I move the bags to a shelf above the hot water heater. Allow the moist seeds to incubate as much as four months if time permits. When seeds fail to root at the next step it is probably due to the insufficient warm incubation.
Every two or three weeks during the incubation period, open the bags and inspect the seeds. Some seeds will be dead and will eventually rot, whereupon they should be promptly removed. If mold appears on the coats of seemingly sound seeds, this may also signal that they are dead. Also, it may be that either the mold or I eventually destroyed their ability to germinate, for I’ve tried washing them carefully and treating them with Captan, but cannot specifically recall germination from any seeds that had become moldy.
5. Rooting period:
Not later than four or five months ahead of the local time for spring planting, move the bagged seeds to a cooler temperature, ranging from 50 to 60 degrees. In Missouri, this should be no later than mid-November. After one week of the lower temperature, some seeds should be found swelled with growth at the hilum (the scar left by separation from the pod) and may have a tiny white root protruding. Some seeds will respond faster than others, and this perhaps is a sign of inherently greater vigor.
6. Repackaging rooted seeds:
Leave the rooted seeds in the bag with their slower mates for up to another month. However, when rooted seeds have been inspected and are being repackaged, I prefer to place them so that there is three inches or more of medium under them in the bag so that the root has space to grow straight down. While experience does not show this to be necessary for the plant, it cuts down on root tangling and permits easier separation of the small plants when next handled.
7. Cold period:
Most of the seeds which have become ready to root during the foregoing sequence will do so within a month after the first roots have appeared. It is now necessary to give the rooted seedlings a period of temperatures around 40 °F which will overcome winter dormancy and release the ability to grow the above-ground portion of the plant, just as is necessary for mature peonies. A household electric refrigerator, cave, cold corner of the garage or possibly a covered window well may provide the desired temperature. Again, keep a thermometer with the seedling bags so that you know what the temperature is.
When the winter dormancy has been diminished for a particular seedling, it will signal its readiness by commencing the extension of its plumule or leaf, comparable to the late winter stretching of peony buds underground. A few seedlings will show this readiness within eight weeks after root growth started, in which case colder temperature down to near freezing may be given to hold them back. Others may take much longer, some requiring twelve weeks or more. If planted in warm soil before this readiness has developed, a seedling is likely to fail. While the soil remains cold, however, the reduction of dormancy can go forward and the seedling may eventually develop. Very slow seedlings may sometimes be brought into planthood by leaving them in a refrigerator until the plumule shows, after which they can be brought out and planted to grow.
8. Planting out:
Germinated seedlings produced by the foregoing method are properly thought of as transplants. When they are ready to grow they may be transferred to pots, greenhouse flats, cold frame or open ground in a well-lighted area. The soil should be free of grubs or other root-feeding soil insects and the area protected from animals by wire mesh or other guard. Squirrels will dig the seeds and pets may break off the shoots. In the Missouri climate some shading from intense sunlight is necessary to avoid sun-burning of the leaves in late June. A shade made of ordinary fly screen has served well for this purpose.
9. Seeds remaining ungerminated:
Seeds that did not root during Step Five, above, may be returned to warm incubation and held for another attempt at rooting in early fall. Unless you are curious to see first hands whether germination takes place, these will be about as well provided for outdoors in a protected site where they are to grow as you can do for them indoors.