Answer: Most commonly available tree peonies are Japanese types (Paeonia suffruticosa), which can't be easily propagated by division, says Scott Reath, owner of Reath's Nursery, growers of more than 300 cultivars of tree peonies in Vulcan, Michigan. Your plant is a yellow flowered tree peony, so it's probably not a Japanese type, but a Paeonia lutea x P. suffruticosa hybrid, which has a large, broad crown with multiple stems and is easier to divide, he explains. Here's what he suggests: In late fall (October in Missouri), carefully clear away the soil from the base of your tree peony by hand and select a healthy stem near the edge of the crown. Using a sharp knife or trowel that's been sterilized in a 10% bleach solution, cleanly cut through the crown, dividing off the stem with some roots attached. Plant the division in fertile soil in a well drained, sunny location two inches deeper than the previous soil level. Fill the soil back around the mother crown to the original level. Mulch the new division to keep the soil warmer and prevent frost heaving. Keep it well watered until the ground freezes. If you division is successful, it will reroot and start growing in spring and flower in two to three years. The mother plant may be set back the first year, but should still flower.
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