Phlox paniculata
garden phlox
polemoniaceae
Large flower clusters in white, pink, red,
purple, or orange; dull green leaves
2–5 ft. high; 2–3 ft. wide
Full sun
Blooms July–September
Zones 4–8
pruning Deadheading prolongs
bloom on plants and prevents reseed-
ing. Seedlings are not desirable,
because they are not true to type and
often take over the more desirable
parent plant. Thinning phlox by a
third or to 4–6 stems is often recom-
mended to reduce the incidence of
powdery mildew, but this is not always
effective and in some years plants get
mildew whether thinned or not. The
gardener needs to decide whether it’s
worth the effort. Plants badly infected
with powdery mildew should be cut to
the ground, making sure to keep them
moist and fertilized for regrowth. Do
not compost clippings. All this being
said, selecting mildew-resistant
cultivars in the first place is really the
best way to avoid the extra mainte-
nance; see the listing of cultivars.
Plants can be pinched or cut back
and shaped to produce shorter plants
and to delay flowering. ‘Flamingo’ can
be cut back by half in early to mid-June,
or 6 in. or more can be cut off when the
plants are in tight bud. Flowering
normally will be delayed by 2 weeks
with pruning, but it can be delayed by
as much as 4 weeks. If plants are cut
back earlier, say in mid-May, flowering
may not be as greatly delayed. Pruning
can be used to produce flowers later in
the season on a few plants or on a few
stems of an individual plant. Flower
size is also reduced with pruning
before flowering, which is nice for
smaller cut arrangements. Stressed
plants or plants in need of division
may have weaker than normal flower
production if pruned.
Be sure to prune down phlox for the
winter if they are affected with mildew.
Clean up and destroy all debris around
the plants to reduce the chances of
infection the following spring.
other maintenance Garden
phlox plants are heavy feeders. They
prefer moist, rich, high-organic soil.
Avoid wet conditions. Give plants
space, good air circulation, and regular
irrigation to help reduce incidence of
mildew. Frequent division, every 3
years, in the spring helps keep plants
vigorous; the double-fork method can
be used. Discard the deteriorated
center of divided plants and leave at
least 3–4 shoots per division. Some
cultivars may require staking.
related plantS The cultivars
listed below are less prone to mildew.
The occurrence of disease may vary
depending on the cultural and
growing conditions for the season or
on the weather, but at least the
chances are better if these more
resistant forms are selected over other
more susceptible cultivars. Some
resistant forms of Phlox paniculata
include: ‘David’, ‘David’s Lavender’,
‘Delta Snow’, ‘Jeana’, ‘Laura’, ‘Lichtspel’
(light show), ‘Natascha’, ‘Peppermint
Twist’, Pink Flame (‘Bartwelve’),
‘Robert Poore’, ‘Shortwood’, and ‘Speed
Limit 45’.Phlox paniculata ‘Flamingo’.
Shorter, fuller, later flowering
results from cutting plants back
by half in mid-June.