Peony

About Peony

Peonies are long-lived perennials with huge, often fragrant late-spring flowers; a happy clump can bloom for 50 years or more. There are three kinds: herbaceous peonies die to the ground each winter, tree peonies are woody shrubs that keep their stems, and Itoh (intersectional) peonies are crosses of the two that have tree-peony-style flowers but die back like herbaceous ones. The ants you see on the buds are just sipping nectar from glands on the bud covers; they do no harm and are not needed for the flowers to open.

Hardy in zones 3-8 and best in 5-7; in warm zones 8-9 some cultivars get too little winter chill, so NC State suggests low-chill types there.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Plant bare-root divisions in early fall (September-October), with 3-5 eyes each. Set herbaceous and Itoh peonies so the pinkish eye buds sit only 1-2 inches below the soil (Clemson says no more than 1 inch in the South); buried deeper, they often won't bloom. Grafted tree peonies go deeper, with the graft 4-6 inches down (Penn State; NC State). New plants may skip blooming the first year and fill out by the third or fourth year (Iowa State).

Soil

Deep, fertile, well-drained soil near neutral; peonies will not stand wet ground (Penn State, Clemson).

Follow a soil test; aim for pH 6.5-7.0 and dig a hole 12-18 inches deep, mixing compost or aged manure into heavy clay (Clemson).

Feeding

• spring, when new stems are 2-3 inches tall: low-nitrogen fertilizer such as 5-10-10 or 5-10-5. Scatter about 2-3 lb per 100 sq ft around (not on) the crowns and water it in (Clemson; NC State). Established clumps only need this every few years (Illinois).

Too much nitrogen and eyes planted more than 2 inches deep are top reasons peonies don't bloom (Clemson; Illinois).

Harvest

Blooms from late spring into early summer (early May in central Illinois); each plant flowers for about two weeks. For vases, cut buds that show color and feel soft like a marshmallow; swish them in water to rinse off ants. Cut no more than a third to half of the flowers, and leave as much foliage as you can on the plant, or next year's bloom suffers (NC State).

Varieties (27)

Pests to watch for

Japanese beetle, Scale insects, Four-lined plant bug

Diseases and problems

Botrytis blight, Leaf blotch, Powdery mildew, Phytophthora blight, Black walnut toxicity

In the kitchen

Keeping it: Buds cut at the marshmallow stage can be wrapped dry and laid flat in the fridge for a few weeks, then recut and put in water to open. In a vase, cut peonies last about as long as roses.

Safety: NC State flags peonies as a problem for pets; we found no research-based guidance on human safety. Don't eat any part.

Pets: Toxic to dogs, cats and horses (ASPCA): paeonol in the plant can cause vomiting, diarrhea and depression.