Thursday, May 30, 2013

Selecting, Planting and Caring for Peonies

We offer both herbaceous and woody (or tree) forms of peonies. The most familiar garden peonies are the herbaceous types, with showy and colorful flowers in May to June, depending upon the variety. Each blooms for a week or more. They are cut down to the ground each fall and rise again in the spring.

Tree peonies maintain woody stems which bear large leaves that drop in the fall, and their flowers are enormous: often up to ten inches across! These blossoms open and fade all too quickly, especially when grown in afternoon sun (although they need at least ½ day of sun to bloom well.) Thanks to the late breeder Mr. Itoh, there are also many “Itoh” or “intersectional” hybrids now available, which have both an herbaceous and a woody parent. These are some of the finest peonies available, with herbaceous foliage resembling that of their woody parent. Enhanced vigor and a longer bloom period, including varieties with yellow flowers, distinguish them from other peonies.

Peonies in The Mixed Border's garden

Flowers are typically classified as Single, which have showy petals surrounding functional carpels and golden-yellow stamens (reproductive parts); Japanese, with large outer petals and clusters of enlarged anthers sometimes edged in yellow; Semi-double, in which inner petals have formed within the ring of outer petals, and still contain functional reproductive parts; and Doubles, whose stamens and carpels have been transformed into a dense display of petaloids surrounded by the outer petals. With the large number of varieties in cultivation, there is often some overlap of these various forms, but I have tried to keep it simple. The Singles and the Japanese forms will tend to remain upright in flower, while the heavier Doubles may flop under their own weight. Support of these types may be recommended to keep the flowers off the ground; a subtle corset of bamboo canes and garden twine is usually enough. Peonies usually require a couple years to get established after planting to display their full floral qualities. Flower color can be affected by strong sun (fading of deeper colors) or cool weather (white varieties can develop pink tones.)

Most (but not all) peonies are fragrant, with the pink or white doubles usually your best bet for a scent that is typically rose-like. Red peonies, though pretty in the garden, don’t always make the best cut flowers, as their aroma isn’t always desirable. Some tree peonies are mildly lemon-scented.

Peony 'Krinkled White'

How to plant peonies:
As long as the planting site is well-chosen and well-prepared, Peonies will live for many decades with little care. Hybrid peonies perform best with at least a half day of full sun, and excepting tree peonies, more is better. If given the choice, some afternoon shade can help to reduce blooms fading in color or “going by” too quickly.

Well-drained soil is important, as areas which remain wet for periods of time may cause their thick and fleshy roots to rot. Because they are so long-lived, they deserve and need a planting hole that is deep and wide, and contains a good amount of organic matter such as compost. Dig a hole at least the size of a 5-gallon bucket and remove the soil, discarding any sand or gravel and reserving the topsoil or loam. To that, add an equal amount of compost (avoid all but extremely well-aged manure) and a handful of lime and organic fertilizer. Fill the hole with this mixture, such that the plant’s soil surface will be at (or slightly above) the soil level outside the hole. Take care not to place soil on top of the roots, either now or at some future time, as their flower buds will not form if planted too deeply. Mulch very lightly with good compost or a thin layer of shredded bark, and water well.

Do not allow the plant to dry out until well-established (usually within one year.) Peonies are drought-tolerant, but may go dormant early and flower poorly (if at all) the next year if not kept reasonably moist throughout the growing season. Fertilize each spring or fall with organic fertilizer.

Peony 'Sorbet'

Peony problems:
My peony doesn’t flower. Why? Peonies planted too deeply may not flower, nor will those grown in poor soil or shade. Keep the foliage vigorous and healthy.

Some of the leaves and flower stems have wilted and turned brown. Botrytis is a blight disease of peonies that happens most often when the foliage remains moist, sometimes due to rainy weather, or because of overhead irrigation (typically from lawn sprinklers.) Clip off the diseased parts, cleaning your clippers with rubbing alcohol between cuts. Throw the diseased stems in the trash. If needed, an appropriate fungicide may be applied as a preventative (but they rarely are curative.)