Tree Peonies: When To Divide Them?

September is the best month to divide or move peonies, and it’s also a good time for other perennials. The main method of propagating tree peonies is by grafting, which is an involved and labor-intensive procedure. However, dividing peonies every three to five years can ensure their health and robustness. The golden period for division is in late September to early October, and the post-bloom phase is crucial.

To divide a tree peony, first have a mature plant that has grown off its graft and set its own roots. Dig up the plant and divide it every three to five years. Each section should have at least three buds and healthy roots to promote regrowth. It’s important not to place the buds in the soil any deeper than 2 inches (5.1 cm).

Dividing peonies is a beginner-friendly task, as they are resilient plants that don’t mind rough handling when being pulled or cut. Follow these steps to divide your peony in late summer or early fall:

1. Cut off all foliage at ground level and dig about 12 inches away from the center.
2. Divide only those growing on their own roots. Tree peonies with only one or two main trunks should not be divided.
3. Collect the ripe seed once the seed pods begin to split in late summer and autumn. Sow the seed 2.5cm (1in) deep in containers.
4. Fall planting occurs from late August until the ground freezes solid for winter. As with all cold-hardy plants, fall is the traditional time to plant and propagate by division. Avoid dividing a shrub with only one or two trunks or stems because they may not tolerate rough handling.

In summary, September is the best month to divide or move peonies, and it’s also a good time for other perennials. The best time to transplant herbaceous peonies is in September, when they’re past their summer growth and entering winter dormancy.