University of Vermont
Department of Plant and Soil Science
Summer News Article
Dr. Leonard Perry, Horticulture Professor Emeritus
University of Vermont
Easy to grow shrubs, hydrangeas include old-fashioned selections as well as
many more recent ones. Many have attractive bark and shapes, they come
in a range of colors, flowers add color to mid and late summer landscapes,
and they make good cut or dried flowers.
To choose the most appealing hydrangea (said as “hi-Drain-gee-ah”), you
should be aware of the several flower types. What we call "flowers"
are actually clusters of flowers, both fertile and sterile. The showy
large parts are the sterile flowers that attract the pollinators to the less
showy fertile flowers. The amount of each varies with cultivar
Then there are clusters that are long and conical (known as panicles), or
flat to convex (known as corymbs). If this latter type is flat,
they're called "lacecaps". If they resemble large balls, they are
called "hortensias" or a name I like "mopheads".
Hydrangeas prefer a moist but well-drained, and fertile, soil. Plant
in full sun to part shade. They can be used in masses, against an
evergreen background, as a specimen plant, or for fresh and dried
arrangements. Flowers of the panicle hydrangea turn a pink fall color,
then a nice tan that remains through winter, as do flowers of the smooth
Not counting the climbing hydrangea (anomala subsp. petiolaris), a
decidious woody vine hardy to USDA zone 5 (-10 to -20 degrees F average
winter minimum), there are four main shrub species. The smooth
hydrangea (arborescens) grows about 3 to 5 feet high and wide, with
rounded white flower clusters of mainly sterile flowers that begin green,
and are long lasting. Since they bloom on current season's growth,
their flower buds aren't winter killed. Plants are hardy to USDA
zone 4 (-20 to -30 degrees F average winter minimum). For best floral
effect and overall plant shape, cut old stems to the ground in late winter
or early spring. This species adds color to woodland gardens, as well
as old-fashioned gardens. The species is native to mountains of the
'Annabelle' is a common and excellent cultivar of the smooth hydrangea, with
large flower clusters 10 to 14 inches wide. 'Grandiflora' is a
cultivar often called snowhill or hills-of-snow, similar to 'Annabelle' only
with smaller flower clusters. White Dome is a patented new cultivar
similar to 'Annabelle' only more vigorous and upright, the flowers tending
not to droop with rain.
The big-leaf or French hydrangea (macrophylla) is the classic one
most know, has most of the newest cultivars, and tends to be the least hardy
(USDA zones 5 and 6). Depending on cultivar, flowers may be either
mophead or lacecap types. These are the ones known for changing color
with the soil acidity. Acid soils free up aluminum, which is what
causes deep blue to purple colors. Alkaline soils result in shades of
pink. This shrub, native originally to Korea and Japan, tolerates salt
such as along roads and the seacoast. Most cultivars reach about 4
feet high and wide. They seldom need pruning but, if so, prune right
after bloom as these flowers on the previous season's growth.
'Nikko Blue' is one of the older and more common big-leaf cultivars, getting
some of the deepest blue colors on its mopheads in acid soils, and is
hardier than most. Similar is 'All Summer Beauty'. 'Red
Star' gets red to purple-red on its lacecap clusters in alkaline soils, and
has attractive fall color. 'Variegata' is interesting both for its
white, irregular margins on leaves, and its pink or blue fertile flowers in
lacecaps surrounded by white infertile flowers. There are several more
compact big-leaf cultivars having mopheads in shades of pink. These
include 'Pia', Forever Pink', 'Tovelit', and 'Glowing Embers'.
Arguably the most publicized new cultivar in recent years is Endless Summer,
touted as having pink or blue mopheads on old (last year’s) and new wood
(this’ year’s growth) most the summer. Although listed as hardy to
USDA zone 4, in my garden in this zone it dies back in winter, with new
growth each summer, but with a short northern-season never blooms. There are
a few other similar and related mophead ones including Endless Summer
Bloomstruck with reddish purple to reddish flowers, Blushing Bride with
white flowers blushed pink, and the pink lacecap type Twist and Shout.
Then there are the panicle hydrangea (paniculata) cultivars, familiar
to many with their large elongated clusters of sterile white flowers, often
seen around Victorian homes. Depending on cultivar, these can reach 6 to 10
feet tall and wide, or more. Native to eastern China and Japan
originally, these bloom on new wood so should be pruned in late winter or
early spring to keep them more tidy. They tolerate a wide range of
soils if well-drained, tolerate urban pollution, and are hardy to at least
USDA zone 4.
The most common panicle cultivar is 'Grandiflora', usually known by the
initials of the species and cultivar names "P.G." or Pee Gee. This
old-fashioned plant is hardy to USDA zone 3 (-30 degrees F average winter
minimum, or lower), and can reach 20 feet tall and wide making a vase-shaped
specimen if pruned. Or, it can be pruned into a single stem with
flowers on top, known as a "standard" or "tree form". 'Compacta' is a
smaller version, only reaching about 4 or 6 feet high and wide. Other
nice selections of the panicle hydrangea include 'Limelight' with lime green
blooms, 'Pink Diamond' with white flowers turning pink early, 'Tardiva'
blooming late, 'Unique' with larger individual flowers than Pee Gee, and
'White Moth' with flowerheads up to 14 inches across.
The Oak-leaf hydrangea (quercifolia) is one I grew up with in the
south, it being native to woodlands and stream banks of the southeastern
U.S. Where it survives into USDA zone 5, it is handsome for its
irregular spreading growth, peeling brown bark, large oak-shaped deep green
leaves, and reddish fall color. It grows in shade, or full sun in the
north. Since this blooms on old wood (the previous year's growth),
prune right after flowering before next year's buds begin to form. It tends
to grow slower than some of the other hydrangeas.
Although the species is a good plant, there are several cultivars you might
consider of the oak-leaf hydrangea. Snow Queen has larger flower
panicles than the species, is showier, and has more upright stems on plants
about 5 feet high and wide. 'Snowflake' may get slightly larger, and
has large, showy, double flower panicles. Perhaps the largest
cultivar, up to 15 feet tall and wide, with both large florets and clusters,
is 'Alice'. 'Pee Wee' and 'Sike's Dwarf' are compact forms, only
reaching about 3 feet high and wide.
If you want to dry hydrangea blooms, especially the panicle ones such as Pee
Gee, there are a couple methods. Although tempting to pick blooms at
peak, they often dry best when cut if they've dried some on the plant
already. The pink tints, if present, hold when dried and give a
Cut long stems, removing leaves, and put in a vase with or without water.
Keep in a dry room, away from direct sun. Or, you can use the
traditional drying method of cutting stems and removing leaves, then hanging
upside down in bunches in a warm, dry, and dark space with good air
circulation. Flowers should be dry in a couple of weeks.
Return to Perry's Perennial