My mother was an avid gardener, and I still remember vividly our back yard as it was when I was a kid — full of lemon lilies, beds of various wildflowers, roses (shrub, not tea), a long line of peonies, and three tree peonies. According to the elderly next-door neighbors, those peonies had been planted right after the first World War; today, they’re over 80 (and still blooming, my brother reports).
Herbaceous peonies are shrubby plants that die down to the ground in winter, whereas tree peonies have branches covered with bark that remain in the garden all year long.
Besides boasting beautiful flowers, the plants themselves are attractive, with glossy green compound leaves set on reddish stems. The genus was named for the Greek physician Paeon, who first used the plants for medicinal purposes. For centuries, the roots were prescribed to treat epilepsy and spasms; today, however, their only use is in the garden. And those ants usually seen patrolling the stems of peonies are interested only in the sweet sap; they don’t damage the plants in any way.
The fall is the best time to plant peonies of either kind, but spring will do just fine. These are plants for which the old axiom of a $5 plant in a $10 hole seems particularly apt: The hole should be big enough to accommodate the plant without crowding the roots. The soil should be rich with added humus (and, if excessively acid, add a cup of lime — well mixed — per plant). Keep manure and added fertilizers away from direct contact with the roots. Plant with the “eyes,” or growing points, to the top, about 1 inch below the soil surface. If you live in a colder climate, it’s a good idea to cover a newly planted tree peony with a large bushel basket for the first winter.
Paeonia suffruticosa, the Japanese tree peony, is originally from China but like many things in the plant world, it was refined by the Japanese. It’s actually a bush, usually reaching a height of 5 feet with a 6-foot spread. The glorious flowers are between 6 and 8 inches across.
Tree peonies are expensive, so shop around for the best price. The tree peony is grafted onto the roots of a regular (or herbaceous) peony, with the graft junction (or joining) about 6 inches below ground level (so the graft will develop its own root system).
Often a newly planted tree peony will produce two kinds of leaves: The deeply cut leaves belong to the tree peony, while the other leaves are shoots from the herbaceous roots and should be cut off at ground level.
I can’t remember seeing a tree peony that did not have exceptional blossoms, but among the more beautiful are ‘Age of Gold’ (with large, double, golden-yellow blossoms); ‘Gauguin’ (with yellow petals inked with rose-red lines); and ‘Marchioness’ (a soft yellow suffused with shades of apricot, all surrounding yellow stamens).