University of Vermont Extension
Summer (early) News
Department of Plant and Soil Science
Leonard Perry, Extension Professor
University of Vermont
Peonies are a favorite herbaceous perennial, being
long-lived, easy to grow, an heirloom plant, and coming in many colors
pink and white in early summer. Here
are a few questions I've received on peonies, and answers that should
have great plants.
"My peonies get tall and flop
over. What can I do to prevent
this?" Many older cultivars
(cultivated varieties) are prone to this, while many new cultivars have
to have stronger stems and to be more stocky.
So it could be just your particular selections. Too little light
also may cause them to grow
taller (and with less blooms). If the
plants are quite old (maybe 15 to 30 years or more), they may need
Some try to stake floppy plants, but
this can be tricky. If you put a cage or
"peony ring" around plants before they get too tall, plants may then
flop onto the top wire and then break there.
The trick is to get tall enough cages or rings to hold plants upright
near the tops.
"When is the best time to
divide peonies, and how often should they be divided?" Peonies can live
lifetime given sun and well-drained soil, and may never need
dividing. If they get too floppy, large, or have few
blooms, dividing may help. It is best to divide plants in the fall
begin to die back, perhaps October. Make
sure to have at least three plump buds or "eyes" at the base on each
division in order for plants to establish well the following year.
"I need to move peonies in
summer, before fall, due to construction.
Is this possible?" Yes it
often is, just make sure if moving
peonies in summer to minimize damage to tops and stems,
get as much roots as possible, keep well-watered when replanting, and
light cloth or fabric over to shade from intense sun. If you can
wait until fall though to move
plants it is much easier with greater chance of success.
"I have ants on my
flowers. Is this bad?" No, the ants are merely after the
secreted by the flower bud scales, or if on leaves perhaps the
aphids. So there is no need to control
them. They myth that ants are needed to
open flower buds is just that.
"My peonies have stopped
flowering. What is wrong?" Did they get too much
mulch? Peonies should be planted at the surface,
with buds no more than two inches deep.
Otherwise they may not bloom. If
mulching heavily around plants, keep the mulch away from the base.
If the buds turn brown and shrivel,
they may have gray mold or botrytis disease.
This often appears in cool and damp weather, and also may cause stems
turn black. Keep plants weeded, with
good air circulation, and water early so plants dry before night.
Sprays are available for this disease. Cool weather also may
blooming later. Another possible cause
for small, unopened buds is the tiny thrips insect.
"My peonies have holes in
leaves, notched edges on others. What is
eating them?" More than likely
slugs are the culprit. These prefer
moist conditions to retreat to during day, such as mulch. Keeping
plants free of mulch, with good air
circulation, may help. There are many
slug control products, just make sure if using poison baits these don't
non-target animals such as pets. Some
use saucers of beer, which attracts slugs.
Others just use boards under plants, or rolls of newspaper. Slugs
crawl under or in these, then can be
"When should I cut back
peonies?" Wait until late fall, or
even early spring, to cut brown or dead stems back. You can cut
them back once foliage has mostly
turned brown in fall. Cut back close to
the ground, as new growth will come from the base next spring.
"Will peonies produce seeds?
" Yes, but this is not an easy way
to start them as they may arise from cross pollination, so not produce
type of plants; their seeds need special germination
requirements; and they are slow to germinate and grow,
taking several years to produce a blooming plant.
"Can peonies be grown in
containers?" Container gardening is
quite popular, even including perennials.
Just make sure if growing peonies in containers that that are large
enough to hold the large root systems as plants grow over the years,
that wont fall over with such large plants resembling
mini-shrubs. Keep in mind peonies are quite hardy in the
ground, yet containers that are above ground and exposed during winter
cold. To prevent peonies, and other
perennials in containers, from such cold roots in winter, bring
a cool, unheated space such as a garage from late fall through later
"What is the best way to
control weeds in peonies?" Good
ground preparation prior to planting, and keeping up with weeds, is the
control. If grass weeds get established
in peonies, there may be herbicides selective for the grass that wont
peonies. Check your local garden store,
and be sure to read the labels.
Otherwise, if peonies become too
weedy, you may need to dig up roots in fall.
Weed the area before replanting, or replant elsewhere into clean
soil. Be aware if using non-selective
herbicides around peonies, such as those with glyphosate or even the
acetic acid (vinegar) based ones, that these can injure or kill peonies
they do weeds.