How Far Apart Do You Plant Peonies?

About Peonies

• Originally from China and Japan, peonies grow from U.S. Department of Agriculture plant hardiness zone 2 through 8 wherever they find enough well-drained, fertile soil and sunshine. Peonies need at least 100 to 300 hours of chilling -- periods where soil temperature registers between freezing and 40 degrees Fahrenheit -- so they do not flower well in areas where sunshine keeps soil warm all winter. Garden peonies are typically herbaceous (Peonia lactifolia or Peonia hybrids). Tree peonies (Paeonia suffruticosa) are less hardy than shrubs, growing from USDA zone 3 to zone 8. Planting of new or divided peonies should be done in fall to ensure spring bloom.

Planting Herbaceous Peonies

• Peony bushes grow from tubers, putting up buds in late winter or early spring; young peonies have as few as a dozen stems, but mature shrubs might measure 3 to 4 feet across. Peonies require well-drained soil, so a 2-foot wide by 2-foot deep hole provides enough room for root growth. The bottom 10 to 12 inches of soil, amended with well-rotted compost, leaf mold or other amendments based on a soil test, provides a fertile, loamy bed for roots. Holes should be dug 3 to 4 feet between centers to allow room for plants to mature. Set the plants in the holes with roots spread and sitting with their buds no more than 1 to 2 inches below the soil surface.

Planting Tree Peonies

• Tree peonies are grafted onto rootstock and grow from 3 to 5 feet tall -- with a crown about 3 feet across. They do not transplant well, so choose their locations with care. The same size hole provides a quick start for roots, but the taller plant needs deeper roots. Set the union of the rootstock and tree’s trunk -- called the graft -- 5 or 6 inches below the soil level. Plant tree peonies at least 4 to 5 feet apart so they receive enough sunlight.

Other Considerations

• Spacing peonies depends on their mature size. Shrubs in an east-west line need wider spacing than those in a north-south line; tree peonies need more space because of their height. Remember that your peony may reside in the same location for 10 or more years before it needs division. To encourage root development, add a cup of bone meal to the bottom of the planting hole. Alternately, add 1/2 cup of superphosphate to each bushel -- 8 dry gallons -- of soil. Regardless of whether fertilizer is added or not, water the peonies in.