Though a few species peonies may be found through specialists’ catalogs and seed exchanges, most garden peonies are hybrids. The basic types are herbaceous and tree peonies, both descended from Chinese species. A new third category, the intersectional hybrids, combines the best traits of herbaceous and tree types. All peonies are extremely long-lived plants of significant size; they provide choice cut flowers and are a mainstay of big perennial borders.
Plant peonies in fall, either as bare-root plants or from nursery containers. Ideally, the planting site for peonies should be deeply dug at least several days before planting. Work in plenty of compost, especially in heavy soil, and incorporate a high-phosphorus fertilizer; then allow the soil to settle before planting.
Peonies of all types can be grown in large (18—24-in.) containers. Replant every third autumn in the same or a slightly larger pot, replacing most of the soil when you do.Paeonia hybrid
An emerging category, the intersectional hybrids combine the best traits of herbaceous (P. lactiflora) and tree (P. suffruticosa) types. They tend to bloom longer than herbaceous or tree peonies because they're sterile, and they come in a wider color range than either parent.
Peonies are extremely long-lived plants of significant size (2 to 4 ft. high and wide); they provide choice cut flowers and are a mainstay of big perennial borders. They demand more than ordinary care in site preparation—but in return for the effort, they can produce flowers of outstanding beauty for a lifetime. Intersectional hybrids leave woody stems standing when they die back after first frost, but since these stems rarely resprout, they’re best cut to the ground; as new growth emerges in spring, spray with copper fungicide. Usually grown on their own roots (compact rhizomes with thick, tuberous roots and several growth buds called eyes).
Clumps grow 2—4 ft. tall and wide (or wider). Handsome leaves are divided and glossy. Large single or double flowers appear in May.
Flower colors range from pure white through cream to pink and red; some of the reds are very deep, with chocolate brown overtones. Depending on variety, blossoms range from 2 in. to as much as 10 in. across; many have a perfume similar to that of old-fashioned roses, though in some varieties the scent is either unimpressive or absent. In form, they fall into three basic categories: single or semidouble, with one or two rows of petals; Japanese, with a single row of petals and a large central mass of narrow petal-like segments called staminodes; and double, with full flowers composed of many petals. In hot-summer climates, choose early varieties such as singles, semidoubles, and Japanese varieties, whose blooms come on before the season heats up. Japanese sorts in particular do well in the warmest zones.
Herbaceous peonies, largely descendants of the perennial P. lactiflora, die to the ground in late fall.
Plant herbaceous peony roots with eyes 2 in. deep in cold climates, 1 in. deep in warmer regions (planting too deeply prevents flowering). Herbaceous peonies do best in pots that are wider than they are deep. In autumn, cut herbaceous peonies to the ground; as new growth emerges in spring, spray with copper fungicide.
Tree (actually shrub) peonies produce flowers on permanent woody branches and are chiefly descendants of P. suffruticosa, a 6-ft. shrub. Tree peonies usually start out as grafts on herbaceous peony roots, but in the long run they do best on their own roots. When shopping for tree peonies, look for plants that have already started to form their own substantial root systems.
Set tree peonies with the graft line 6–8 in. below soil surface (the aim is to get the shrubby top graft to root on its own). In cold-winter areas, plant at least 6 weeks before the ground usually freezes; mulch only after the ground has frozen. Plants are unlikely to bloom the first spring after planting, but they should bloom every year after that. with handsomely divided blue-green to bronzy green leaves. Single to double flowers, typically very large (to 10–12 in. across), appear in spring.
These peonies seldom show their full potential until they have spent several years in the garden, but the spectacular results are worth the wait. Catalogs offer named varieties of Japanese origin in white and shades of pink, red, and purple. These are generally semidouble and display their flowers well. Some of the older European hybrids in pink and yellow are fully double,with flowers so heavy they hang their heads. More recent and more expensive hybrids come in yellow, copper, and a coral that approaches orange; all result from crosses of P. suffruticosa with P. delavayi and P. d. lutea. These bear semidouble blooms that face outward and upward.
Tree peonies require much less winter chill than herbaceous peonies. The large flowers are fragile and should be sheltered from strong winds. Snip off blooms when they fade.
After leaf drop in fall, prune to remove dead wood and to control the height of mature plants; do this by removing about half the current season’s growth on the tallest branches that have bloomed, always making your cuts just above an outward-facing side branch.
In coldest climates, protect from winter sun and wind with a burlap curtain.
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