Q. An established row of peonies is growing along our property line
in full sun. We had beautiful blooms the past couple years, although
the plants have been neglected. This year, the plants look fine and
are full of buds, but the buds are not opening. What is the problem,
and what can we do about it?
the buds look as though they are drying up and dying without
opening, it could be peony botrytis. We had cool, wet weather in May
as the peonies were starting to grow, creating ideal conditions for
this fungal disease also known as gray mold, the most common disease
of herbaceous peonies. The warm spell that followed brought many
peonies into bloom, followed by rains that shattered those delicate
flowers into moldering masses of goo that stuck to the wet plants,
enhancing the development of mold.
Symptoms of Gray Mold Disease
Irregular dark brown leaf spots
are characteristic of this disease. Buds form but often turn dark
brown or black and dry up rather than opening. On buds and petals,
you can see a brownish-gray fuzz. This is the fruiting body of the
fungus and comprises thousands of microscopic spores that are spread
by wind, splashing rain or irrigation water, and on tools or even
your hands when you work on infected plants. The fungus survives on
plant debris and can persist in the soil for many years.
Pink peonies in full bloom
dispose of all the decaying and infected plant parts. Do not compost
it. Thoroughly deadhead them when they finish blooming, and do not
hesitate to remove badly spotted stems to the ground while doing so.
Clean up plant debris around your peonies during the growing season
and again before putting the garden to bed in the fall. Cut
herbaceous peonies (but NEVER tree peonies!) to the ground and
dispose of the cuttings.
cannot keep them dry when it rains, avoid wetting the foliage when
you water. If your peonies are very old and overcrowded, it may be
helpful to divide them. This will improve air circulation inside the
plant, which helps the foliage dry faster after rain. Late summer
(mid-September) is the best time to divide herbaceous peonies. Try
to have four or five "eyes" per division, and avoid planting them
deeper than 1-1/2 to 2 inches. If peonies are planted too deeply,
they will not bloom in future years.
You can also
make fungicide applications to the new growth next spring to protect
it from botrytis, especially if the weather is cool and wet when
young shoots start poking up through the ground. Mancozeb is labeled
to control botrytis on peonies. Organic gardeners can use Serenade
biofungicide (Bacillus subtilis, QST 713 strain). Follow label
directions regarding application rate and intervals between
applications. Both products perform best if used preventatively when
environmental factors are favorable for disease development.
Remember that fungicide applications are not a substitute for good
garden sanitation and maintenance, but they are a partner to them.
a slightly acid soil pH, between 6.0 and 7.0, so it would be wise to
obtain a soil test kit from your local cooperative extension office
so that you can amend your soil back into the preferred range.
Plants grown in accordance with the cultural preferences are less
likely to suffer serious insect or disease problems than those
growing where they do not belong.
It is helpful to
realize that not all peonies bloom at the same time. I was at
Fellows Riverside Garden in Youngstown, Ohio, the first Saturday in
June, and not all of the peonies in its sizable collection were open
Easy to Grow
Lawn snow mold