are workhorses in the garden. They produce sumptuous petals of color
to add beauty to your garden. But they need not be forgotten once
their flowers have died. Hydrangeas can be captured easily in dried
flower arrangements, providing the last gasp of the summer garden.
Pick the blooms on a clear dry day in late summer and hang to dry.
H. macrophylla and H. paniculata 'Grandiflora' are
especially good for drying.
species of hydrangeas can be grown in either full sun or partial
shade. They are resistant to most insects and diseases. They can
be grown in a wide range of soil but prefer a rich, moist soil and
should be planted where watering will not be a problem. Avoid dry
windy sites, as their large, soft leaves lose water quickly, especially
on hot, windy days, causing the foliage to wilt.
are produced on the new growth; therefore, it is important that
hydrangeas be given some care each season to ensure that vigorous
new growth occurs. Irrigate plants weekly to replace moisture loss.
Prune flower stems after they have bloomed.
hydrangeas in early spring with a complete granular fertilizer at
the rate of 2 pounds per one hundred square feet. Apply fertilizer
as broadcast top dressing. During long periods of drought, water
thoroughly each week.
There are many different types of hydrangeas; many require different
methods of pruning. First, one must know the identity of the hydrangea
in the landscape, so the proper pruning procedure can be implemented.
arborescens 'Grandiflora' -- Hills-of-Snow Hydrangea
Prune hills-of-snow hydrangea to the ground line each winter
or early spring because it flowers abundantly on new growth, and
is frequently killed back during winter. If a larger shrub is desired
(3+ feet) and/or it is not killed back over the winter, prune less
severely. Remove certain branches to the ground; cut others back
at varying heights from 1 to 3 feet.
paniculata 'Grandiflora' -- Pee Gee Hydrangea
is the most commonly planted hydrangea because of its massive displays
of large white flowers in mid-to-late summer. They gradually turn
to pink and remain on the plant in a semi-dried condition long after
the leaves have fallen. Pruning involves the removal of dead flowers,
if unattractive, and an annual corrective pruning of vigorous shoots.
Thin and/or cut back the previous season's growth in late winter
or early spring, since flower clusters occur on newly developing
branches. Without regular pruning, this hydrangea can rapidly become
quite overgrown and out of scale in the landscape. It can, however,
be developed into a single or multi-stemmed tree form.
macrophylla -- Hortensia or Florist Hydrangea
This is a commonly grown hydrangea with large globe-shaped flowers.
It is frequently forced by florists and sold as an indoor pot plant
during the spring season. Once moved outdoors, however, color is
dependent upon the pH of the soil in which it is grown: blue if
acid; pink if alkaline. There are also several white-flowered cultivars.
Pruning can be accomplished at two different times. Late summer
is more desirable, since most hortensia types flower only from the
end buds of upright or lateral shoots produced during late summer
and fall of the previous season. Prune as soon as the flowers have
faded and strong shoots are developing from the lower parts of the
stems and crown. Remove at the base some of the weaker shoots that
are both old and new. Always try to keep several stems of old productive
wood, with a sufficient number of stout new stems that will flower
the following season. Early spring pruning (March), although acceptable,
will result in the sacrificing of bloom for that growing season.
this species too late in the fall (after September) is harmful.
New growth, both vegetative and reproductive, will not develop proper
maturity. Hortensia is a good seashore shrub; flowering is more
profuse in an open, sunny location. This, however, increases its
vulnerability to bud killing. Winter protection of the plant should
be initiated in December to preserve buds for next year's flowering.
Tie the shoots together and wrap with burlap. If left unprotected,
delay any spring pruning until the buds swell in order to determine
which wood needs to be removed, and then cut back to below the point
quercifolia --Oakleaf Hydrangea This plant is grown primarily
for its handsome oak leaf-shaped foliage, excellent fall color,
attractive flowers and interesting winter bark. It is ideally suited
to a lightly shaded or protected location, and if grown in an exposed
site, it is subject to some winter dieback. Prune back in early
spring to remove dead wood. Cut back to below the point of injury
and remove old wood to the base.
anomala petiolaris -- Climbing Hydrangea Climbing hydrangea
is a desirable mid-summer flowering woody vine that attaches itself
by aerial roots to brick, masonry or wood. It requires little or
no pruning. If certain shoots have grown out of bounds, reduce their
length in summer. Frequently, concern is expressed about climbing
vines that may be inundating a tree and causing irreparable damage.
There has never been a proven case of damage occurring from climbing
color of the pink and blue varieties is determined by the degree
of soil acidity. Pink varieties develop color best in the greenhouse
at a soil pH of 6.5 to 7.0., while the best blue color occurs at
pH 5.0 to 5.5.
hydrangea flower is small and insignificant but is surrounded by
showy bracts. The anthocyanin pigment will be pink or blue, depending
upon the incorporation of either iron or aluminum in its molecules.
Insufficient aluminum is absorbed by the plant at a pH of 6.5 to
7.0 so iron is used.
the pH drops to 5.0 to 5.5, aluminum becomes more soluble, is absorbed
by the plant and becomes part of the anthocyanin molecule resulting
in blue coloration.
hydrangeas contain no pigment in their sepals (although some may
develop as the blossom ages). They may be grown as either pink or
blue, the only indication being given by the small petals. Common
white varieties are Sister Therese and Regula. Rose Supreme, Merritt's
Supreme and Merveille are examples of varieties which can be blue
or pink depending on soil conditions.
maintain pink coloration, enough limestone should be incorporated
in the soil at the time of planting to keep the pH at the above
aluminum necessary for blue color will become soluble in nearly
any soil at a pH of 5.0 to 5.5. Depressing the pH with aluminum
sulfate will also supply soluble aluminum. Since soluble phosphates
precipitate aluminum, a fertilizer containing low phosphorous or
none at all should be used (13-0-20 and 15-0-15 are examples).
these methods of changing the flower color can be used, it's not
a wise idea to do it indefinately. You risk severely altering the
soil pH thereby making it difficult for the plant to utilize nutrients.
Always get the soil tested before altering it. Refer to
GreenShare Factsheet on soil testing for more information. If
you really like different colors in your hydrangeas then get many
you obtain a potted hydrangea for Easter or Mother's Day in full
bloom, keep the soil moist at all times as this plant has a high
water requirement and tends to dry rapidly in the home. It should
also receive direct light.
the flowers fade, they may be removed and the plant treated as a
house plant. When danger of frost is past, it can be planted in
a sheltered location in the garden. Shelter is necessary because
the hardiness of this plant is questionable in our northern gardens.
This plant forms flower buds in the fall like forsythia and dogwood.
It is these buds which freeze out or are destroyed in colder climates.
Many times the plant will survive and produce green leaves, but
no flowers. Planting in a sheltered location plus covering the plant
with burlap will offer some protection. If you wish to improve the
probability of flower bud survival, you may wish to try this.
danger of frost is past, plant in a sheltered place in the garden.
On the 4th of July, prune to 3 to 5 inches from the ground. The
plant will produce short branches terminating in a dormant flower
bud. Before the temperature falls to 25 degrees F, place a screen
around the plant. Fill this with an insulating material such as
coarse peat moss, vermiculite or bark. More material may be added
if it settles during the winter. Remove this protection when the
crocuses flower but protect on cold nights. If you are lucky, the
flower buds will survive. In any event, you should have a pretty
If you are successful in over-wintering these varieties, fertilize
with your usual garden fertilizer (such as 5-10-10). If you desire
blue flowers, have your soil tested as a low pH is needed. 'Nikko
Blue' is a common true blue variety. To lower the pH, apply aluminum
sulfate or sulfur. Avoid over acidification and "playing" with the
soil chemistry and plants. For pink flowers, limestone may be necessary
to raise the pH since soils are naturally acidic in Southern New
England. Always choose varieties for the colors you like.
you are not successful in over wintering greenhouse varieties, hardy
hydrangeas are available. Some are: Hills of Snow Hydrangea (H.
arborescens Grandiflora, similar to the greenhouse varieties),
Pee Gee Hydrangea (H. paniculata Grandiflora) or Climbing
Hydrangea (H. anomala petiolaris).
by Rosanne Sherry, URI Master Gardener Coordinator, 7-98
Based on fact sheets from Cornell-Suffolk Co. Long Island New York
Cooperative Extension, Connecticut Cooperative Extension and Virginia