Ahh, the tree peony, elegant queen of the garden. Tree peonies create giant blooms in an array of soft or shocking colors, making them the centerpiece of color-themed cottage gardens or the foundation element in more formal French-style gardens. Once you introduce these beauties to your perennial beds, you'll wonder why you waited so long to bring them home.
Keep in mind that shrub peonies are long-lived plants and with a little care produce blooms for a century or more. Depending on the zone where you live, a mature tree peony could set 100 flowers in a season! It only takes 5 to 10 years to reach maturity, so these stately shrubs quickly take their royal places.
Tree peonies are perennial shrubs and need different care than regular garden peonies. Don't ignore other peony advice, but do try these tips and tricks for best success.
Transplanting Tree Peonies
Buy your new shrubs from a reputable greenhouse. You may get them bare root but it's better if they've been growing on in a greenhouse pot. It's easy to bury bare root plants too deeply, but when transplanting from a greenhouse pot you already know where the soil line should be.
Tree peonies make an excellent flowering hedge and thrive along fences, but allow 3 feet between each transplant for good air circulation. Mature tree peonies can reach 4 to 5 feet in height and width. Crowding the plants invites diseases and pests, but tree peonies don't mind co-mingling branches with neighbors.
Amend the soil with compost or well rotted manure. Whatever amount of soil you take out for the hole, add 1/3 that volume in amendments and mix thoroughly. If your soil is heavy, add sand to lighten. Some plant experts recommend peat moss for increasing the friability of soil, but tree peonies like a neutral pH so peat moss may not work for you.
Once they're established, tree peonies don't like to be disturbed. If you need to move them for some reason, do so in the spring before they break dormancy and preserve as many roots as possible.
Sun, Food and Water Requirements for Tree Peonies
Six hours of sun per day is sufficient (partly shaded). Protect from hard afternoon sun. Shrub peonies bloom best when the weather is cooler so watch out for reflected heat from buildings or fences.
Do not fertilize right away—wait four weeks, then add balanced fertilizer to the soil around the plant. Water adequately for the first two years; tree peonies are drought tolerant once established.
Ongoing Care for Tree Pronies
Deadhead spent peony blossoms to keep the plant clean, but it will not rebloom. Tree peonies are shrubby and do not die back in the fall. Please don't cut them. Protect with burlap sacks or some other kind of shelter if you live in a snowy place. Mulch around the base of the plant over winter with straw or fallen leaves and cover with canvas or burlap for extra protection. Remove winter mulch completely in the spring. Sprinkle a little garden lime around the plants in the fall (1/8 inch or less, only around the plants; “sugar coat”).
The following varieties should be available at Beier's Greenhouse this season, but they tend to sell out quickly. Call ahead if there's a particular variety you absolutely must have.
Hanakisoi Pink “Floral Rivalry” Tree Peony
Double ruffled flowers with dark pink centers and light pink edges. Blooms on mature Hanakisoi peonies can be 10 inches in diameter. Blooms late spring to early summer for 2 to 3 weeks; flowers last longer in cool weather. Gray green oblong leaves and red tinted stems.
Companion plants for Floral Rivalry peonies: scabiosa butterfly blue (pincushion flower); corydalis lutea (yellow); Siberian Iris in blue shades; geraniums; cerastium tomentosum (snow in summer).
Shimadaijin Purple Tree Peony
Glowing semidouble blossoms in reddish purple. Flowers are 6-10 inches across.
Companion plants for Shimadaijin Purple tree peony: Daylilies; most varieties of white-blooming perennials.