After peonies and irises have bloomed, a tuber grows on the ends of the stalks. Can I plant those and expect to have a new plant? I know all the instructions of peonies say to dig up the plant and separate. My peonies are not big enough to do that yet but want to propagate in another area of the yard. Also, if it is not advisable to plant those tubers, should I be cutting back those stalks? Also, my irises have created what look like 3" tubers after they finished blooming. Can I plant those like a root to start a new plant? If not, did I wait too long to cut back the stem?
Peonies and Irises
Certified GKH Gardening Expert
Peonies are usually propagated by grafting or root division. Many peonies are infertile and do not produce seeds. Irises occasionally produce seed pods but these, too, will take some time to propagate by this method and, therefore, division of the rhizomes is recommended. If you would like to try your hand at starting the seeds anyway, it's at lest worth a shot.
Collect the seeds as soon as the pods begin to open. Place them in a sealed plastic bag with barely moist vermiculite or soil-less germination mix. Place the sealed bags in a warm area and ensure they remain moist (but not wet). Leave them there until roots appear, which can take anywhere from a few weeks to several months. Once roots appear and are about an inch long, move the bag to a cool location, such as a refrigerator, for about 10-12 weeks, after which pot them up in a soilless germination mix. Note: seeds can also be sown directly in the ground provided the conditions for dormancy and growth are present. However, it will usually take until the second spring before any shoots appear.
Peonies can be cut back to the ground in fall. As for the iris, do not cut back the foliage. Instead, allow this to die back naturally as the plants need this in order to produce enough energy for making next year's blooms.