Peony Terms

If you plant more than one variety of peony, you can have up to seven weeks of bloom time, from late May until early July in the Twin Cities. Areas like Duluth may still have bloom as late as mid-July. Knowing a bit about these long-lived plants makes it easier to decide which ones to grow.

Bloom times, details

  • Very early (weeks 1–2): fernleaf (U036, P467) and other species (U039), plus woody peonies (U041–U047)
  • Early (weeks 2–3): single hybrids (P464, P476, P477a, P480)
  • Mid (weeks 3–4): double hybrids (P472), ­singles from this page
  • Mid-late (weeks 4–5): many semi-doubles and doubles from this page
  • Late (weeks 5–6): Japanese (P468, P479)
  • Very late (weeks 6–7): a few hybrids, plus the Itohs (U037, U038)
  • Hybrids nearly always have only one bud per flower stem while P. lactiflora has from three to 12 side buds.
  • Most hybrids have strong stems that do not require support. 

The late bloomers are sensitive to temperature. If summer heat arrives early, many of the cultivars in weeks 5–7 may open at nearly the same time. If we ease into summer, we have a longer period of bloom.

Bloom types

Peony blossoms come in a range of different forms. Chinese growers list 15 different forms, while the American Peony Society currently uses just six. Here is the APS list.

Single: A single row (or, at most, two rows) of petals surround a central group of fuzzy, yellow, pollen-bearing stamens, with a small ­cluster of carpels in the very middle. 

Japanese: Marked by a large, ­central cluster of stamens that have all been transformed into very slender petals called staminodes. Usually the edges and tips of the staminodes are yellow.

Anemone: A version of the Japanese type, but the staminodes are even more petal-like and are now referred to as petaloids. The petaloids are almost always a ­single color.

Semi-double: Two, three, or more rows of petals with some irregularly shaped petaloids. In some cases the yellow ­stamens are mixed in with the petaloids; in others there is a distinct center of stamens and carpels (the pollen-receiving parts of the flower).

Double: Many layers of ruffled petals. Usually no ­stamens are visible since most have become petals. Sometimes a thin ring of stamens is seen among the petals.

Bomb: Typically, the center segments form a round ball, sitting on top of a lower ring of “guard” petals, which are ­sometimes a different color. (The word “bomb” probably comes from bombe, which is the name of a round, frozen dessert popular after WWI.)

We hope these guidelines help you vary the bloom times and forms of your peonies to bring almost two months of beauty to your garden.


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