Tidewater Gardening - October 2010


October is Peony Time
K. Marc Teffeau


October is a good time to sow a number of plant species in the landscape. The soil is still relatively warm which will encourage good root growth. Balled and burlapped trees and shrubs, container-grown ornamentals and most perennials can still be planted. October is also a great time to renovate the perennial flower bed, clean up dead and diseased leaves and cut out the dead flower stalks. I would wait until after the first or second hard frost to mulch the perennial bed, however.
The usual recommendation is to plant perennials in the spring, however, with the availability of material in containers, the planting season often extends well into the summer and early fall, with autumn planting continuing until the end of October in our area. Just remember, the earlier perennials are planted, the better the root system will be when the plant enters the winter. Late fall plantings can sometimes result in frost heaving and loss of perennials.
Containerized perennials should be planted at the same depth they were grown in the container. Planting too high results in plants drying out, and too low invites crown rot. Some perennials such as bleeding heart, iris and peony need shallow planting in order to flower properly. Containerized plants should be watered before planting and bare root perennials should be soaked in water for one hour prior to planting in order to re-hydrate the plants.
A perennial that you definitely want to plant in the fall is the peony. Peonies are perennials favorites in the flower garden. Few herbaceous plants can rival them for floral display and foliage. Their exquisite large blossoms, that are often fragrant, make excellent cut flowers and the foliage provides a background for annuals and other perennials. Two types of peonies are generally known in our area landscapes; the Paeonia spp. hybrids (garden peony) and Paeonia suffruticosa (tree peony).
Peonies are long-lived perennial flowers that produce large blooms in the spring. Colors include black, coral, cream, crimson, pink, purple, rose, scarlet, white and yellow. By planting early, mid-season, and late flowering cultivars, you can have peonies flowering for 6 to 8 weeks.
Garden peonies are herbaceous perennials (20 to 36 inches in height) grouped into five types according to flower shape: single, semidouble, double, Japanese and anemone. Support is often required for tall, double hybrid garden peonies.
Tree peonies produce large numbers of flowers on a shrub-like plant. The stems do not die back each year.
The rest of the comments in this article will be about garden peonies. If you would like to see a nice selection of peonies, I would recommend that you check out the Mid-Atlantic Peony Society at http://midatlanticpeony.org/gallery/.
Peonies grow best in cool climates. Some mail order catalogs provide a rating range from 100 to 300 chilling hours per winter for cultivars. In our area, try to select cultivars with a lower chilling requirement.
Garden peonies grow best in full sun, but will tolerate light shade. Peonies require winter cold to flower. To encourage flowering, plant on a northern exposure and do not mulch in the winter. The planting site should have protection from strong winds, but be well aerated to reduce disease problems. Peonies prefer a well-drained soil with a pH of 6.0 to 7.0 Roots will quickly rot in poorly drained soil so you might consider planting them in a raised bed. Try to avoid locations where peonies have been grown before.
The best time to plant garden peonies is in early fall – September and October are ideal. If planted in the spring, they may not bloom for a year or two. Purchase divisions containing 3 to 4 “eyes.” Divisions with only 1 or 2 eyes normally take three to five years to flower.
Be sure the divisions are free from rot when they are planted. Trim away any soft spots with a sharp knife. Dig a hole about 12 to 18 inches deep and 18 inches wide, spacing the holes three to four feet apart. Incorporate a 2- to 4-inch layer of organic matter such as compost, pine bark or well-aged manure. Add ¼ to ½ cup of a balanced commercial fertilizer like 10-10-10, or an organic fertilizer with a similar proportion, per plant in the bottom of the hole. Avoid adding fertilizer to soil that will surround the roots. Many gardeners add a half cup of bone meal or superphosphate at planting. Remember, peonies are more or less permanent plants in the garden and they have deep roots; the only time you can properly prepare the soil is prior to planting.
Fill the hole about half full of amended soil, then place the root division with the eyes facing upward. After the division is in place, work the soil in around the fleshy roots. Be sure the eyes will not be more than 2 inches below the soil surface when backfilling is completed. If planted in September to early/mid October, the clumps should be partially established before severe cold weather occurs.
Mulch peonies each spring with a 2- to 3-inch layer of organic matter to control weeds, conserve moisture and keep the soil cool. In the fall, remove and destroy the old mulch to aid disease control. Leave the plants unmulched during the winter.
Maintain adequate phosphorous levels in the soil for healthy, vigorous root development and growth. In the spring, apply a low analysis nitrogen fertilizer at the rate of 2 to 3 pounds per 100 square feet per plant when the stems are about 2 or 3 inches high. Over-fertilization, especially with nitrogen, will result in weak stems and reduced flowering.
To produce large flowers, a practice known as disbudding is recommended. The terminal bud on each stem tip is left and all side buds are removed. This should be done as soon as the buds are visible. To prevent the large flowers from breaking or bending over during a strong wind or rain, plants should be staked.
Remove flowers as soon as they fade to prevent seed development which can use up needed food reserves. The faded bloom should be removed just below the flower, leaving as much foliage as possible.
Cutting flowers for enjoyment in the home can also reduce flowering in future years. Do not cut more than one-third to one-half of the flowers for arrangements and leave as much foliage on the plant as possible.
In the fall, after a heavy frost, remove and destroy the stems of garden peonies down to 3 inches from the soil surface to eliminate the possibility of the fungal diseases overwintering. Peonies do not respond well to transplanting and reestablish slowly. Divide and replant only after they have become crowded – usually after 10 to 15 years. Each plant requires an area about three feet in diameter.
Peonies may be left undisturbed for many years. A decline in flower production usually indicates overcrowding and the need for division. Carefully lift the clump and wash away the soil to expose the eyes. Using a clean, sharp tool, divide the clump into sections, each with 3 to 5 eyes and good roots. Replant immediately.
Peonies have few pest problems. The most frequently occurring pests in our area are botrytis blight and leaf blotch – both fungal diseases. Especially prevalent during wet springs, botrytis affects leaves, stems and flowers. Spots appear on the leaves, stems soften and decay and flowers either rot or buds blacken and fail to open. Prompt removal of infected material and a thorough fall cleanup are essential for control.
Leaf blotch develops during warm, moist weather. Glossy, dark purple spots form on the upper surfaces of the leaves. Again, removal of infected leaves and good fall cleanup are necessary for control. Avoid overhead irrigation.
The only insect pests of any consequence on peonies are scales. Scales are seen on stalks and leaf bases in late summer and overwinter on the below-ground portion of stalks. The presence of ants on peony blossoms is neither beneficial nor harmful to the plants – they are simply attracted to the sugary liquid secreted by flower buds.
Happy Gardening!!