Types of peonies: herbaceous, tree, intersectional
I've grown peonies in my zone 7a Long Island garden for over 15 years. The first peony I planted was a pale pink herbaceous type bought at a big-box store with no cultivar name on the label. It bloomed the following May in large double flowers that nodded to the ground in the first rain and has.
I've grown peonies in my zone 7a Long Island garden for over 15 years. The first peony I planted was a pale pink herbaceous type bought at a big-box store with no cultivar name on the label. It bloomed the following May in large double flowers that nodded to the ground in the first rain and has since grown into a substantial clump that blooms reliably every spring.
The three main peony types — herbaceous, tree, and intersectional — differ in cold hardiness, when they bloom, what happens to their stems in fall, and critically in how deep to plant them. The planting depth rules are different for each type, and confusing them is the most common cause of failure.
Herbaceous peonies (Paeonia lactiflora and hybrids)
Herbaceous peonies die completely to the ground each fall and regrow from fleshy storage roots each spring. They are the most widely available peony type and the most cold-hardy.
Per Penn State Extension, herbaceous peonies are reliably hardy in USDA zones 3–8. They require a cold dormancy period of approximately 300–500 hours below 40°F, which limits their performance in zone 9 and warmer.
Planting depth: Per Penn State Extension, the most critical rule in herbaceous peony culture is planting depth. Eyes (red growth buds on the crown) must be no more than 1–2 inches below the soil surface in zones 4–7. Eyes planted deeper than 2 inches may produce vigorous foliage but will not bloom. This is the most common reason peonies fail to bloom.
Flower forms in herbaceous peonies:
| Form | Description | Examples |
|---|---|---|
| Single | 5 petals; visible stamens | 'Scarlett O'Hara', 'Krinkled White' |
| Japanese | Ring of guard petals; center of narrow petaloids | 'Bowl of Beauty', 'Gay Paree' |
| Anemone | Guard petals plus dense mass of petaloids; no visible stamens | 'Angel Cheeks' |
| Semi-double | Multiple rows of petals; partially visible center | 'Coral Charm', 'Do Tell' |
| Double | Fully filled with petals; no visible center | 'Sarah Bernhardt', 'Festiva Maxima', 'Karl Rosenfield' |
Per Missouri Botanical Garden, double-flowered types are the most popular but tend to flop in rain due to the weight of the flower head. Single and Japanese forms have better stem strength and are more accessible to pollinators.
Bloom season: In zone 6–7, herbaceous peonies bloom May–June. By choosing early-, mid-, and late-season cultivars, the bloom window can be extended over 4–6 weeks.