Few plants bestow upon a garden understated sophistication and regal splendor as surely as do tree peonies. This is my first blog-post on Port Washington Patch about what I have learned during 20 years as a professional garden designer, horticulturist, and plantsman.
As distinguished from herbaceous peonies, which are cut to the ground in early autumn, tree peonies are woody plants, shrubs really, that leave a visible framework through winter -- and do not need staking. Nor do they require any annual pruning. Easily reaching a height and width of five feet (in 12 years), they should be more or less left alone, although I do like to remove their leaves to the trash as they fall (or before they do), because they can be susceptible to a fungus. They prefer dappled shade or full-sun in the morning with some afternoon shade. Peony flowers last less than a week and too much sun wilts them into dehiscence. As with any planting, relieve compaction to a generous diameter and depth, and amend with compost, especially where the soil has been disturbed by construction.
Tree peonies were first cultivated and prized in imperial China (moutan), but I have always grown the Japanese cultivars because they are less extravagantly enormous and heavy: their stems can support their weight. In any case though, if the flowers absorb rain they will droop badly -- or the dozens of petals will fall to the ground. However, a tree peony in leaf is a handsome element in a mixed border.
They are expensive. Now is good time to source and order them. Often one sees them labeled merely "red" or "pink." I avoid these and search instead for named cultivars. In recent years there have emerged numerous new American-bred cultivars. Unless you find a tree peony in a garden center, in which case it will be in a 2- or 3-gal pot and it will have one or more flower buds, when you mail-order it will not likely flower the first year. However, I can attest that tree peonies in my gardens always are in flower at the end of the first week of May, with lilac, wistaria, Spiraea x vanhouttei, columbines, and forget-me-nots -- which, most years, coincides with Mother's Day! And they are very, very long-lived plants.