Most modern garden varieties of peonies (Paeonia spp.) are hybrids, the result of years of breeding for selection of hardiest or most ornamental plants. The cold winters and rather short but warm summers in Michigan are ideal for growing peonies. Long-lived perennials, peonies appreciate a sunny location and a deep, fertile soil that has good drainage. The ideal planting time is September. Overly wet soils or high humidity leads to fungal problems on leaves, stems or roots. Peonies grow well across all of Michigan, which ranges across U.S. Department of Agriculture Hardiness Zones 3 through 6.
Herbaceous peonies are so-named because their non-woody stems die back every autumn after hard frosts occur. Most modern varieties of herbaceous peonies derived from the species Paeonia lactiflora, although other species from eastern Asia are used in breeding today as well. A wide array of flower colors are available, typically ranging in color from white to pink and red, with shades of red-violet or burgundy possible. Varieties also differ in size of flower, number of petals, fragrance, or precise timing of bloom in spring or early summer across the state. Example variety names of herbaceous types include: Sarah Bernhardt, Angel Cheeks, Mrs. F.D. Roosevelt, Coral Charm, Pink Parfait, Scarlett O’Hara and dozens of others.
Tree peonies are those that grow woody stems that persist over winter, rejuvenating new leafy and flower growth in spring and summer. According to Reath’s Nursery in Vulcan, Mich. both species and hybrid tree peonies exist and grow well in Michigan gardeners. Species Paeonia suffruticosa is usually known as the Chinese or Japanese tree peony and there are many varieties, such as Five Continents, Cardinal Vaughan and Rimpo. Hybrid tree peonies originate by crossing Paeonia suffruticosa with Paeonia lutea or Paeonia delavayi. Thus, the flower color range for tree peonies extends well beyond the pink, white and red range to include yellow, purple and even tones of golden orange.
Among the most cold- tolerant of peonies, fern-leaf peony (Paeonia tenuifolia) is not as widely known or grown as either herbaceous or tree types aforementioned. Excellent even in USDA Zone 3, fern-leaf peony is herbaceous and is attractive from spring to fall since its light green leaves are so frilly with thin, deep lobes. It flowers in mid spring in lower Michigan to late spring in the Upper Peninsula, with deep red flowers with yellow centers. Variety Plena bears blooms with extra flower petals.