minimal or no deadheading. With
older plants, deadheading greatly
increases the length of the bloom
period. Deadheading also prevents
seeding. Don’t be too much of a
neatnik, however; leave some heads
for the gold finches, who feed on them
heavily in August but will frequent the
plants as soon as seed is available.
Some seeding can create a nice effect
in the garden, as plants come fairly
true to seed. Since heliopsis can be
short-lived, seeding may also be the
only guarantee of longevity in the
garden.
In certain years the entire plant
may need to be cut down after flower-
ing, around mid-September, if it has
gotten tatty from sooty mold (remains
of heavy aphid populations) or mildew
or just wear from a long summer.
Otherwise you can leave the plants up
for further bird feeding. Selective
cutting back of the worst stems or
deadleafing of the worst leaves can
also help keep the appearance
presentable.
Plants respond well to cutting back
before flowering to reduce the mature
height and delay the bloom period.
Three-foot-tall plants cut back by half
in early June matured to 3 1/2 ft.,
compared to the 5-ft. unpruned plants,
and they started blooming 1 1/2–2 weeks
later and consequently flowered that
much longer. Pruning in this way can
be used to reduce the height of some
individuals and create a nice layering
effect for a planting, or to have
different plants in different parts of
the garden flowering at slightly
different times. It provides flowers for
arrangements over a longer period as
well. Heliopsis probably could be
pruned back even more for shorter
plants, or pruned slightly later,
perhaps in mid- to late June, for an
even greater delay.
other maintenance Fairly
low-maintenance perennial once
established. First-year plants some-
times struggle to take hold. Prefers
moist, organic soil but tolerates short
periods of drought. Plants grown in
rich conditions may need division
every 2–3 years in the spring or fall to
increase longevity; otherwise plants
can usually go 5 years before division
is needed. Red aphids usually attack
the plants starting in May. They don’t
do much harm, unless a plant is badly
infected, in which case the unsightly
sooty mold that follows can literally
cover the plant. Wash heavy aphid
populations off with a strong spray of
water. Beneficial soldier beetles may
help control pest infestations.Heliopsis helianthoides ‘Summer
Sun’. Plants in the front were
pruned by half in early June.
They matured to 31/2 ft., rather
than the typical 5 ft., and started
flowering about 2 weeks later
than unpruned plants.