Dr. Leonard Perry, Horticulture Professor Emeritus
University of Vermont
Few perennials can offer what the peony does--beautiful, prolific flowers in early summer and good foliage afterwards. Once established, peonies will flower for many years with minimum care. What's more, they’re extremely hardy and can easily withstand cold northern winters.
The basic types of peonies are herbaceous (Paeonia officinalis), which grow to heights of two to four feet; fern-leaved (Paeonia tenufolia), with finely dissected leaves; and bush or tree (Paeonia suffruticosa),
which may reach four to six feet. The latter produces many flowers on
woody, shrub-like plants. Then there are the hybrids with flower colors
of the tree peonies, yet habit of the herbaceous peonies. These
hybrids, and the tree peonies, often are quite expensive.
Most gardeners seem to have better luck growing the herbaceous forms.
However, don't rule out tree peonies if they are hardy in your area.
When fully mature and in full bloom, they are spectacular.
Peonies are usually planted in the fall from bare roots, although
they may be purchased in the spring or summer as potted plants. They
should be planted in an area that receives at least six to eight hours
of sun per day. When grown in shady areas, they will produce good
foliage but few if any flowers.
The prime prerequisite for good growth and flowering, as with most
perennials, is a well-drained soil. You may need to add organic matter,
such as coarse sphagnum peat moss, rotted manure, or similar material to
the soil before planting. Dig it in deeply.
When planting, set the tuber (thickened root) of the herbaceous peony
so the buds will be between one and two inches below the surface of the
soil. Don't plant them any deeper because this will produce lots of
foliage but few, if any, flowers. The buds or “eyes” on the tubers are
bright red, and about one-quarter to one-half inch long. Generally,
herbaceous peonies from bare roots will flower the second year after
Tree peonies are grown from seeds or grafts, though most home
gardeners have greater success with grafted plants (in which the desired
variety has been attached to a different, often more vigorous,
understock plant). It will take at least three years for a grafted tree
peony to flower. When planting the tree peony tubers, dig a hole deep
enough to cover the graft with four or five inches of soil. To locate
the graft, feel the plant to find the ridging on the stem and the
different texture of the bark. By planting deep, the grafted section
will establish its own roots in the soil.
After planting any peony, water thoroughly. Mulch with two to three
inches of straw, shredded bark, or wood chips kept away from stems.
This prevents too much moisture and rots, and prevents the buds of
herbaceous types from being too deep.
Next spring, once the plants start to grow and shoots reach three to
four inches high, apply a complete, dry fertilizer such as 5-10-10 or
6-10-4 at three to four pounds per 100 square feet of bed area. Or use
an organic fertilizer such as 5-3-4, with about one-half cup evenly
spread around the plant. Water the fertilizer into the soil immediately
after application. You also can use high analysis soluble fertilizers,
applying them at the rate given on the container. Only one application
of fertilizer is generally needed per year to maintain good plant growth
Peonies tolerate low fertility, but bloom better with more. Too
much, however, and you may end up with all leaves and few flowers.
Yearly additions of compost around plants may be all that is needed in
fertile soils, and in any soils is beneficial.
If you have an older cultivar (cultivated variety) of peony, you may
need to put a peony cage or similar frame around plants in early summer
to lessen toppling later. Newer cultivars have been bred to be more
upright, sturdy, and seldom need staking.
Keep in mind peonies grow quickly and large early in the season,
based on the stored food in the tubers from the previous year. The
critical time for this food storage is early to mid summer, so if
conditions are dry, make sure plants get plenty of water at this time.
This will result in better blooms the following year. When watering, it
is best to not water next to the stems, but rather in a circumference
around the plant canopy.
Providing good air circulation, removing old or diseased flowers, and
removing leaves in the fall will help prevent leaf diseases and gray
mold on flowers. Ants on flowers do no harm, and are temporary, so
should be ignored and left alone. These are merely after nectar on some
flowers, and possibly other attractants. They may even help open tight
double buds on some.
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