Herbaceous peonies (Paeonia spp.) grow well across all of the Northeast — generally the region and states to the north and east of Philadelphia. Here, in U.S. Department of Agriculture hardiness zones 3 through 7, peonies bloom in either May or June. Peonies are long-lived plants that form a dense clump of stems and downward-growing fleshy roots (tubers). Often gardeners don’t need to transplant peonies less than once every ten to 15 years. Reduced vigor, overcrowded plants, or relocating peonies to a sunnier garden spot are reasons to consider transplanting them, but never when they’re preparing to or during bloom.
Things You’ll Need
- Hand pruners
- Sprinkling can
- Wait to dig up and transplant peonies until the fall. Cornell Cooperative Extension (New York) suggests waiting until early September before considering the task while Dr. Leonard Perry from the University of Vermont suggests waiting until the first fall frost nips back the peony foliage before transplanting, perhaps October. Overall, the time frame from Labor Day to Halloween seems to be a good guideline. Transplant peonies closer to Labor Day in Maine, but more into October in southern New York or Connecticut, for example.
- Prune back peony stems and foliage by 50 percent in height with a hand pruners or heavy duty scissors. Place the cutting debris in the compost pile to decompose. This reduces the water-absorbing burden on the roots as well as gives you a much better view of the area you dig to lift the peony plant.
- Slice the garden shovel blade into the soil about 6 inches way from the stems in the peony clump. Drive the blade 10 to 12 inches. Rock the blade back and forth slightly to loosen the soil, but do not lift up until the soil is cut all around the peony clump — you don’t want to snap any main vertical tubers in the center of the clump when digging.
- Lift the clump of peony stems and roots from the hole, trying to retain as much soil around the tubers as possible. Place the root ball into a wheelbarrow to move the plant to the new planting site that receives a minimum of 8 hours of direct sunlight. The area should be uncluttered with other plants, at least 3 feet wide to house the planting hole.
- Dig a hole at least twice as wide as the peony’s clump of roots and tubers and equally as deep. Since peonies resent root disturbance and go into transplant shock, you want to improve the planting site now since it will be years before you’ll transplant it again. Add 2 to 4 inches of rich compost to the pile of soil outside the hole and blend it in well.
- Place the peony clump into the hole, holding it upright with one hand and then glancing down to note if the root ball is at the same planting depth as previously grew. Look at the transition area between the stem bases and the tubers. You will see a pinkish knob at the top of the vertical tubers: this is an "eye." The eye is the growing point from where the peony root sprouts next year’s stem in spring. The eyes of all tubers must be planted no deeper and no shallower than 1 to 2 inches from the soil surface.
- Backfill the planting hole with the compost-amended soil, tamping the soil gently as the hole fills. Pay close attention to the depth of the tubers’ eyes. They must not be any deeper than 2 inches; too deeply planting peonies results in no production of flowers later on.
- Water the newly transplanted peony with a sprinkling can. Add enough water to soak the soil to a depth of 6 to 12 inches. Monitor the planting area over the fall, ensuring the soil is always evenly moist but never soggy. Once the soil freezes in late fall or early winter, watering is no longer necessary.
Tips & Warnings
Spring digging and planting as the new reddish growth is just emerging is the second best time to transplant if fall isn’t an option. If construction or other untimely emergency warrant moving and transplanting of peonies, keep the roots evenly moist if planting is from late spring to late summer. Cut off flowers if present so the roots focus energy on growing and sustaining leaves to re-establish.
If the peony root ball is too large and you wish to divide it and get multiple clumps to plant, slice into the root ball with the shovel blade or a long knife. You want at least three to five healthy tubers that have at least three to five eyes per clump to transplant.
Don’t expect a spectacular flowering display the next or second year after transplanting the peony. Some flowers are produced, but up to three years of undisturbed growth gets this perennial back to its former blooming glory.