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W 304
A Tennessee
Landscape
Contractor’s Guide
to Hydrangeas
Cover Photo Credit Carol Reese
Hydrangea arborescens ‘Annabelle’
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H
Landscape Use
Hydrangea species exhibit a range of foliage, flower and
growth characteristics as well as tolerance to environmental
conditions. They are found in every size and shape from
small trees and shrubs to vines. Some species have striking
fall color. All hydrangeas in cultivation have large,
ornamental flowers. They are virtually pest free and easy to
grow when planted in the proper place. Hydrangeas can be
found throughout the United States from U.S. Department
of Agriculture plant hardiness zone 3 to zone 9. For these
reasons, hydrangeas are versatile plants and can be used in
several areas of the landscape, including a shrub or
perennial border, foundation or mass planting, or as a
climbing vine or specimen plant (Figures 1a, 1b and 1c).
Species Overview
Hydrangea anomala subsp. petiolaris, climbing
hydrangea
Climbing hydrangea is slow to establish but can cover large
areas once it has matured. Climbing hydrangea creates
visual interest with its branch structure (Figure 2a). White
flowers bloom from late June to early July and have a sweet
fragrance (Figure 2b). Fall color is usually nonexistent, but
the peeling bark provides winter interest. Climbing
hydrangea is hardy from zones 4 to 8. While beautiful
specimens occasionally can be found in the upper South,
climbing hydrangea is not very common in Tennessee due
to its slow growth rate in our warmer climate. Consider
Whitney M. Yeary, graduate research assistant
Department of Plant Sciences
Amy Fulcher, assistant professor for sustainable ornamental plant production and landscape management
Department of Plant Sciences
A Tennessee Landscape Contractor’s
Guide to Hydrangeas
Introduction
Hydrangeas are some of the most popular plants in the green industry. As a professional landscape
contractor, you are likely planting or maintaining many types of hydrangeas on your clients’ properties.
This publication is designed to provide basic information on hydrangea selection and care for
Tennessee landscape professionals. For more in-depth information or for guidelines on producing
hydrangeas commercially, please see the IPM for Shrub Production Manual listed in the References
and Resources section.
Figure 1a, Photo Credit Amy Fulcher
Bigleaf hydrangea as a shrub border, defining a patio area.
Figure 1b, Photo Credit Amy Fulcher
Mass planting of oakleaf hydrangea in full sun.
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Japanese climbing hydrangea, Schizophragma
hydrangeoides, as a faster growing alternative. While not a
hydrangea botanically, it resembles climbing hydrangea. It
has an abundance of white flowers, blooms from a young
age, and quickly establishes and fills an area. ‘Moonlight’ is
a popular cultivar with attractive silver foliage.
Figure 1c, Photo Credit Andrew Pulte
Mass planting of hydrangea spp.
Figure 2a, Photo Credit Jason Reeves
Climbing hydrangea covering brick wall.
Hydrangea arborescens, smooth hydrangea
Smooth hydrangea is a native hydrangea that can be grown
in zones 3 to 9. Typically, smooth hydrangeas grow into
symmetrical clumps approximately 4 feet by 4 feet. Flowers
can be extremely large (up to 1 foot across), globular and
bloom en masse in early to mid-June (Figures 3a and 3b).
Bloom time can last two months, and blooms can be so
large that their weight may cause the branches to flop.
Many notable smooth hydrangea selections currently are
available in the trade. ‘Grandiflora’ was the smooth
hydrangea standard for many years, but it has since been
replaced by ‘Annabelle.’ ‘Annabelle’ features somewhat
stronger stems than ‘Grandiflora,’ but they can still be
floppy. A new selection, Incrediball, has bigger flowers than
both ‘Grandiflora’ and ‘Annabelle.’ ‘Ryan Gainey’ is a
popular cultivar notable for strong stems. Invincibelle Spirit
is a new release with pink flowers, a novelty for this species.
Hydrangea macrophylla, bigleaf hydrangea*
Bigleaf hydrangea typically grows 4 to 6 feet tall and wide.
Flowers of certain selections of bigleaf hydrangea change
Figure 2b, Photo Credit Jason Reeves
Climbing hydrangea blooms.
*Bigleaf hydrangea and the closely related H. serrata, mountain
hydrangea, are discussed together in this section and the
“Pests” section.
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color depending on aluminum availability, which is affected
by soil pH. However, some cultivars will bloom white
regardless of aluminum levels. Plants typically bloom in
Tennessee beginning in late May through June. Aging
blooms persist into the fall when they dry but remain
attractive. Bigleaf hydrangea does best in a moist but well-
drained soil, and numerous selections can be grown in
zones 6 to 9. Bigleaf hydrangea cultivars are separated into
two groups: lacecaps (Figure 4a) and hortensias, commonly
called mopheads (Figure 4b). Lacecaps have smaller, less
showy fertile flowers surrounded by large sterile flowers,
while mopheads have essentially all sterile flowers in solid
masses borne in round corymbs. Some of the top
performing mopheads (not including remontant selections)
out of 250 selections evaluated by Plant Introductions Inc. in
Watkinsville, Ga., are ‘All Summer Beauty,’ ‘Ami Pasquier,’
‘Frillibet,’ ‘Générale Vicomtesse de Vibraye,’ ‘Mme. Emile
Mouillère,’ ‘Mousseline’ and ‘Nikko Blue.’ Top performing
lacecap selections are ‘Blue Wave,’ ‘Lanarth White,’
‘Lilacina,’ ‘Veitchii’ and ‘White Wave.’
Figure 3a, Photo Credit Andy Pulte
‘Annabelle,’ smooth hydrangea.
Figure 4b, Photo Credit Amy Fulcher
Blue example of hortensia group, H. macrophylla.
Remontant Hydrangeas
Remontant means that a plant flowers more than
once in a single season. This type of plant is often
referred to as a “repeat bloomer.” Top mophead
remontant selections include ‘Blushing Bride,’ ‘David
Ramsey,’ ‘Decatur Blue,’ Endless Summer (‘Bailmer’),
‘Mini Penny,’ ‘Nantucket Blue,’ ‘Oak Hill’ and ‘Penny
Mac.’ Twist-n-Shout is the only remontant lacecap
type. Some bigleaf hydrangea cultivars are more
strongly remontant than others. The “less remontant”
cultivars will rebloom best if pruned after the first flush
of flowers. Fertilizing remontant hydrangea selections
also helps support repeat blooming.
Figure 4a, Photo Credit Amy Fulcher
Pink example of lacecap group, H. macrophylla.
Figure 3b, Photo Credit Andy Pulte
Dinner plate-sized inflorescence, ‘Annabelle,’
smooth hydrangea.
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Hydrangea paniculata, panicle or hardy hydrangea
Panicle hydrangea is a fast-growing species that can reach
20 feet in height and spread and be trained as a small tree,
but many newer cultivars remain small and compact.
Panicle hydrangea is a tough, adaptable hydrangea that
grows best in zones 4 to 8. Unlike most other hydrangeas, it
can tolerate urban environments and drier soil conditions.
The flowers (panicles) are generally borne on strong, upright
stems; however, several cultivars, such as Little Lime, can
be floppy when in bloom. Flowering occurs from mid-July to
September depending on your location in Tennessee.
Flowers begin white and, depending on the cultivar, can age
to a light green or change to a pinkish-rose color. However,
it is important to note that even selections that claim to have
pink flowers may remain white in Tennessee and farther
south. ‘Grandiflora’ has panicles that can reach 18 inches in
length and 12 inches in width, although typically the flowers
will be only 6-8 inches long. ‘Limelight’ is a large cultivar,
reaching 10 feet in height (Figure 5). Little Lime is the dwarf
version of ‘Limelight,’ growing to just 5 feet tall. Both
‘Limelight’ and Little Lime have abundant flowers that can
age to an attractive pink. ‘Phantom’ is a new cultivar with
strong stems and exceptionally large flowers that open
earlier than ‘Limelight.’ Pinky Winky bears large, white
flowers from mid- to late summer; sepals turn from white to
pink as they age. Then, as new white florets develop at the
tip of the panicle, the flower becomes multicolored. Quick
Fire is a newer selection that blooms earlier than most
panicle hydrangeas, from mid- to late May through late June
in Middle Tennessee. Flowers age to a bright reddish color.
Hydrangea quercifolia, oakleaf hydrangea
A native of the southeastern United States, oakleaf
hydrangea grows well in zones 5 to 8. Oakleaf hydrangea
can grow at least 6 feet tall, and typically is at least as wide
as tall. Flowers start white and often change to pink
(depending on the cultivar and weather) and then brown as
they age (Figure 6). Oakleaf hydrangea blooms from late
May through July. Fall color is exquisite, especially when
compared to other hydrangea types, with a mixture of red,
orangish-brown and maroon colored leaves (Figure 7).
However, like most plants, fall color can vary from year to
year. Oakleaf hydrangea has attractive exfoliating bark
(Figure 8), which contributes to visual interest throughout
the year. Plants perform best when the roots are kept cool
and moist but not wet. Popular cultivars of oakleaf
hydrangea include ‘Snowflake,’ which has 12- to 15-inch-
long, draping panicles made of stacked sepals (Figure 9)
that create a unique double-flowered appearance. ‘Alice’ is
a large, vigorous cultivar (12 feet tall by 12 feet wide) with
10- to 14-inch-long panicles that age to a rose color. ‘Snow
Queen’ has larger, upright and more abundant panicles than
the straight species in such that they blanket the shrub with
Figure 5, Photo Credit Amy Fulcher
‘Limelight’ panicle hydrangea in bloom.
Figure 6, Photo Credit Amy Fulcher
Oakleaf hydrangea in bloom in woodland garden.
Figure 7, Photo Credit Amy Fulcher
Range of fall color within one oakleaf hydrangea plant.
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blooms. ‘Munchkin’ and ‘Ruby Slippers’ are compact
oakleaf hydrangeas, approximately 3.5 feet tall and 5 feet
wide, making them ideal for small landscapes. They
produce many flowers held above their foliage that open
white but turn pink with age. ‘Ruby Slippers’ has flowers
that are larger than ‘Munchkin’ and turn deeper pink in
color. ‘Little Honey’ is another small hydrangea (4 feet tall by
4 feet wide) from which golden foliage emerges, changing
to chartreuse by midsummer and becoming a rich scarlet
color in the fall if it receives adequate sun exposure
(Figure 10).
Pruning and How It Affects
Blooming
Hydrangeas generally require little pruning. When they do
need to be pruned, it is usually to reduce or reshape plant
size, remove unsightly or dead stems, or rejuvenate older
plants. To decide when to prune — as with all flowering
Figure 8, Photo Credit Amy Fulcher
Exfoliating bark, oakleaf hydrangea.
Figure 9, Photo Credit Amy Fulcher
‘Snowflake’ oakleaf hydrangea has a novel double flowered
appearance.
Figure 10, Photo Credit Jason Reeves
‘Little Honey’ oakleaf hydrangea.
shrubs — first determine if the plant blooms on last year’s
growth or the current season’s growth. Smooth
hydrangea, which blooms on the current year’s growth,
should be pruned back by early March so the plants have
plenty of time to grow stems and form flower buds. For
bigleaf hydrangea, once plants are mature prune a few
(no more than one-third) of the older branches to the base
of the plant in early spring. This pruning will rejuvenate the
plant without a large loss of flowers. If major pruning (size
reduction or shaping) is needed, it is best to prune after
blooms fade but no later than the end of July. Pruning isn’t
necessary for panicle hydrangea. However, cutting the
plants back hard, to approximately two buds, can create a
more tidy appearance and increase the size and number of
blooms. Blooms will form on the new stems, so this pruning
can be done once plants go dormant through early March.
Unlike other hydrangeas, panicle hydrangeas can be trained
to a tree form. This training should begin at an early age in
the nursery and will often require a stake. To maintain the
tree form, remove branches that develop from the trunk
several times throughout the year. Oakleaf hydrangea
should be allowed to grow in its natural form and pruned as
little as possible. Oakleaf hydrangea flowers are produced
on old wood. If pruning is necessary, finish by the end of
July so there is time for next year’s flower buds to form.
Climbing hydrangea rarely requires pruning; stray
branches can be removed as needed.
Be aware that severely pruning an established, healthy
hydrangea that has become overgrown will only temporarily
solve the problem. It likely will be just as large within a
couple of growing seasons. To avoid this issue, it is
important to know the mature size of the hydrangea desired
and to select the appropriate cultivar for the location.
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Care of Hydrangeas
Hydrangeas can be grown in relatively poor soil; however,
they grow best in fertile soil with a high percentage of
organic matter. Soil should be moist but well drained. Use
mulch to help retain soil moisture. Location is also very
important, as too much shade will decrease flowering and
too much sun will cause plants to wilt. The exception is the
panicle hydrangea, which needs at least six hours of sun to
flower. For best results, plant hydrangeas where they
receive morning sun and afternoon shade or dappled shade
throughout the day. Fertilize and adjust pH based on the
results of a soil test. Too much nitrogen can lead to
excessive foliage at the expense of flower production. When
planting hydrangeas, dig the hole at least twice as wide as
the size of the plant container but no deeper. Plant “at
grade” so the plant is not deeper nor shallower than when in
the container. Mulch and water thoroughly at planting.
Watering
Hydrangea roughly translates to “water lover” in Greek
(“hydra” meaning “water” and “angeon” meaning “vessel”).
Once planted, hydrangeas should be watered consistently
throughout their first year. Even after establishment, most
hydrangeas need at least 1 inch of water per week either by
rainfall or by irrigation. More water may be needed in a
sunny or windy location. Proper location and ample
mulching reduce the amount of irrigation that is needed.
Although hydrangeas are “water loving,” overwatering can
be a problem, causing root issues and stunting growth. It is
important to note that a bigleaf hydrangea — even one that
is irrigated — can wilt midday in the summer, especially
when it is windy and dry. This wilting often indicates that the
plant can’t take up water as fast as it is being lost from the
leaves to the environment, not that the soil is too dry. Be
careful not to overwater in this situation.
Why Hydrangeas Don’t Bloom
If a hydrangea is not blooming, it could be due to too much
nitrogen, too much shade, pruning at the wrong time
(removing the wood containing the flower buds), or winter
injury to flower buds. Too much nitrogen stimulates
excessive vegetative growth at the expense of flower
development. Heavy shade reduces flower production.
Hydrangeas bloom best with three to four hours of morning
sun (See the “Care of Hydrangeas” section). Bigleaf and
oakleaf hydrangeas form flower buds in late summer and
fall, so pruning during winter or spring and severe winter
temperatures can prevent flowering (See “Pruning and How
it Affects Blooming”). Homeowners sometimes plant florist
bigleaf hydrangeas received as gifts in the landscape. These
bigleaf cultivars do not have winter hardy flower buds and
aren’t suited for landscape use in Tennessee.
Hydrangeas for Cut Flowers
For clients who are interested in cut flowers, planting
hydrangeas can offer months of floral display. Almost any
hydrangea can be used as a cut flower. However, the best
cut flower hydrangeas are those that have few or no fertile
flowers as fertile flowers tend to shed. The average cut
flower has a vase life of about seven days, but some panicle
hydrangea selections and ‘Annabelle’ smooth hydrangea
have a vase life of 18 and 10 days, respectively, when no
preservative is used. Vase life of these hydrangeas can be
extended up to 25 days if a preservative is used. In the fall,
hydrangea flowers dry nicely if left on the plant and can be
used in dry flower arrangements.
Pests
Hydrangeas tend to be problem-free in the landscape, but
they are not immune to insects and diseases. The most
common disease problem is powdery mildew (Figure 11),
which can be severe when 1) environmental conditions are
conducive to infection and 2) a susceptible selection is
used. In addition, bigleaf and oakleaf hydrangeas can get
bacterial and fungal-borne leaf spots.
Keeping the leaves dry and the humidity low within the plant
canopy can help reduce the occurrence of both powdery
mildew and leaf spots. Good air circulation and sunlight
penetration into the canopy will help keep leaves dry and
reduce humidity in the canopy. Begin managing diseases at
the time of design and installation by planting in a location
with a desirable amount of sunlight, spacing plants an
appropriate distance apart, and accounting for the mature
size of the plant. In addition, careful pruning can increase air
circulation and light penetration.
Figure 11, Photo Credit Alan Windham
Powdery mildew, a disease of hydrangeas.
In some cases, fungicides may be necessary to prevent
extreme plant stunting and disfiguring of leaves from
powdery mildew. They also can be used to prevent infection
or stop the spread of leaf spots. However, taking no action
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is a viable option as the spots, while unattractive, do not
generally threaten plant health.
In addition to powdery mildew and leaf spots, hydrangeas
are susceptible to several ring spot viruses and other
viruses, but they are not common. Root rot also can be a
concern. If plants are properly sited in well-drained soils and
are not over-irrigated or subjected to excessive runoff, root
rots often can be prevented. Oakleaf hydrangea is the least
water-loving hydrangea. Take extra care to ensure that this
species will not be too wet.
Arthropod pests of hydrangea include aphids, Japanese
beetles, leaf tiers, spider mites and rose chafers, but insect
and mite pests are rarely serious. Hydrangeas can be
sensitive to herbicides; so, use herbicides carefully, if at all,
around hydrangeas. Always read the product label before
applying a pesticide!
Using resistant selections is a great way to reduce pest
problems and minimize or even eliminate the need for
pesticides. It is also a key component of Integrated Pest
Management, or IPM. Selecting for pest resistance is a
major objective of hydrangea breeding and evaluation
programs. Some of the more disease-resistant bigleaf
hydrangea selections include ‘Amagi Amacha,’ ‘Lilacina,’
‘Lady in Red,’ ‘Shirofuji,’ ‘Veitchii’ and ‘White Wave.’
‘Veitchii’ is resistant to both powdery mildew and bacterial
leaf spot. Follow the University of Tennessee Institute of
Agriculture’s current research to identify disease-
resistant selections.
How to Adjust Bigleaf Hydrangea
Flower Color
Bigleaf hydrangea selections have pink, blue or white
flowers. For those that can be pink or blue, how pink
or blue they will be is controlled both by the genetic
capability of the selection and by aluminum availability
in the soil. The more aluminum a bigleaf hydrangea
takes up from the soil, the bluer the flower color will
turn, deepening until it reaches its maximum genetic
color potential (Figure 12a). Likewise, less aluminum
means pinker flowers to the extent that the genetics
of that selection allow (Figure 12b).
The availability of aluminum for uptake by plants is
affected by 1) the amount of aluminum present in the
soil, 2) the soil pH, which controls how accessible alu-
minum present in the soil is, and 3) phosphorus lev-
els. In soils with a high pH, most of the aluminum
present in the soil is not available to plants. However,
at a pH of 4.5-5.5, aluminum that is present is readily
available. Therefore, a high soil pH will create pink
flowers despite the amount of aluminum present in
the soil. Too much phosphorus can make aluminum
unavailable to plants. Conduct a soil test to determine
pH, aluminum and phosphorus levels prior to planting
and approximately every two years thereafter during
landscape maintenance. Apply sulfur or aluminum
sulfate according to soil test recommendations. To
lower pH, incorporate sulfur several months before
flowering occurs, but take care that the pH does not
fall below 4.0 as it can be damaging to roots. Applica-
tions made after planting should be raked into the
soil. As hydrangeas have become more popular, spe-
cialty hydrangea fertilizers have been developed in-
cluding those that are low in phosphorus.
Figure 12a, Photo Credit Amy Fulcher
A lower pH (4.5-5.5) will cause blue flowers on bigleaf hydrangea.
Figure 12b, Photo Credit Amy Fulcher
A higher pH will cause pink flowers on bigleaf hydrangea.
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Acknowledgements:
The authors gratefully acknowledge the practical experience, observations and willingness to share by
Mark Halcomb, Andy Pulte, Sandra Reed, Carol Reese, Jason Reeves and Alan Windham, all of whom
made this publication possible. Their invaluable expertise and photographs greatly improved this
publication. The authors also would like to express their gratitude to Sue Hamilton, Carol Reese, Jason
Reeves and Tom Samples for their careful review, which greatly enhanced the quality and utility of
this publication.
References and Resources
Damm, C. and M. Miller. 2003. Hydrangeas in the landscape. Extension Factsheet HYG-1063-03.
http://ohioline.osu.edu/hyg-fact/1000/pdf/1063.pdf.
Dirr, M.A. 2004. Hydrangeas for American gardens. Timber Press, Portland, OR.
Dirr, M. 2009. Manual of woody landscape plants: their identification, ornamental characteristics,
culture, propagation and uses. Stipes Pub., Champaign, IL.
Dirr, M.A., 2012. Hydrangeas: Breeding, selection, and marketing. Plant Introductions, Inc. Watkinsville,
GA. http://www.plantintroductions.com/hydrangeasbreedingselectionandmarketing.html.
Dunwell, W., D. Wolfe, and J. Johnson. 2001a. Hydrangeas for cut flowers: Two years of bloom data
observations. University of Kentucky Nursery and Landscape research report. PR450. Lexington,
KY. http://www.ca.uky.edu/agc/pubs/pr/pr450/PR450.PDF.
Halcomb, M., S. Reed, and A. Fulcher. 2013. Hydrangeas. UT-UK IPM for shrub production manual.
A Fulcher, ed. Knoxville, TN. http://plantsciences.utk.edu/tnsustainablenurserycrops.htm.
Leeson, T., R.E. McNeil, J.S. Snyder, S. Bale, and W.C. Dunwell. 2008. Post-harvest vaselife evaluation
on two cultivars of Hydrangea paniculata. 2007 UK Nursery and Landscape Program research
report. PR 554. Lexington, KY. http://www.ca.uky.edu/agc/pubs/pr/pr554/pr554.pdf.
Leeson, T., R.E. McNeil, J.S. Snyder, S. Bale, and W.C. Dunwell. 2008. Post-harvest vaselife evaluation
on Hydrangea arborescens ‘Annabelle’. 2007 UK Nursery and Landscape Program research report.
PR 554. Lexington, KY. http://www.ca.uky.edu/agc/pubs/pr/pr554/pr554.pdf.
Reese, C. and J. Reeves. No date. Hydrangeas pruning fertilizing! UT Extension Handout.
USDA. 2010. 2009 Census of horticulture specialties. Washington, DC.
http://www.agcensus.usda.gov/Publications/2007/Online_Highlights/Census_of_Horticulture_
Specialties/.
Windham, M.T., S.M. Reed, M.T. Mmbaga, A.S. Windham, Y. Li, and T.A. Rinehart. Evaluation of
powdery mildew resistance in Hydrangea macrophylla. 2011. Journal of Environmental Horticulture.
29(2):60-64. http://www.hriresearch.org/index.cfm?page=Content&categoryID=174.
Associations
American Hydrangea Society http://www.americanhydrangeasociety.org
Mid-South Hydrangea Society http://www.midsouthhydrangeasociety.com
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Programs in agriculture and natural resources, 4-H youth development, family and consumer sciences, and resource development. University of Tennessee Institute
of Agriculture, U.S. Department of Agriculture and county governments cooperating. UT Extension provides equal opportunities in programs and employment.
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