Feeding: Peonies are heavy feeders. D’Aoust recommends top-dressing them each fall with a five-centimetre layer of homemade compost or well-rotted cattle manure. If you prepare your soil well, peonies planted in sandy soil won’t need to be fed until their second autumn. (According to D’Aoust, peonies grown in clay soil never need fertilizer.) Apply in a circle about two centimetres from the crown. Caution: Don’t dump material directly on the crown of the plant—you could injure the slender leaf stems.
Bone meal has been touted as a peony fertilizer, but modern steamed bone meal is virtually devoid of nutrients. If you prefer to feed with commercial granular fertilizer, a balanced formula such as 10-10-10 is recommended. Avoid lawn fertilizer, which is too high in nitrogen (the first number, representing nitrogen, should never be higher than the next two, phosphorus and potassium). Apply about 60 mL (1⁄4 cup) around each plant (away from the crown) in late fall and at flowering time.
Watering: Peonies like well-drained soil—standing water or “wet feet” is fatal to them—and they’re reasonably drought-resistant. However, clumps newly planted in sandy soil benefit from weekly watering during their first summer if rainfall is not adequate. Subsequently, water plants whenever there’s a dry spring, and give them a deep watering every couple of weeks or at least once a month in hot, dry summers. According to D’Aoust, peonies planted in clay rarely need watering if top-dressed with five centimetres of mulch.
Staking: Early-summer thunderstorms are notorious for pelting blowsy, double-flowered peonies into the soil. To prevent this, install sturdy hoops or homemade supports of bamboo sticks and twine in early spring when leaves begin to emerge. Don’t leave the job too late, as peonies leap with astonishing speed from tiny, reddish shoots to knee-height. (Avoid tomato cages, as they taper toward the plant crown and can damage roots when pushed into the ground.)
Fall cleanup: Cut down and remove peony foliage after a killing frost (old foliage can harbour pathogens, such as botrytis, that thrive in cold, wet weather). Discard diseased leaves; don’t compost them. If you live in a cold climate—average minimum temperatures below –28°C—with unreliable snow cover, add a layer of winter mulch such as leaves or evergreen boughs. Remove mulch in early spring before new growth emerges.
Division: A peony clump will grow happily in the same garden spot for many years. However, if you want more plants or you notice the plant is producing fewer and smaller flowers because of increasing shade or overcrowding, division is the answer; the time to do this is early to mid-autumn. If you have to move established clumps, divide them before replanting, as huge clumps don’t re-establish well.
To divide a peony, carefully dig out the entire clump and wash away soil, exposing the roots and eyes. With a clean, sharp spade or knife, separate clump into sections, making sure each section has good root mass and three to five eyes. Replant divisions as soon as possible.
Top photo: 'Adolphe Rousseau' (week 5) by Tracy Cox.