''Hydrangea macrophylla'' is a species of
flowering plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...
in the
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Hydrangeaceae
Hydrangeaceae is a family of flowering plants in the order Cornales, with a wide distribution in Asia and North America, and locally in southeastern Europe.
Description
The genera are characterised by leaves in opposite pairs (rarely whorled or ...
,
native
Native may refer to:
People
* '' Jus sanguinis'', nationality by blood
* '' Jus soli'', nationality by location of birth
* Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory
** Nat ...
and
endemic
Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
to Japan.
It is a
deciduous
In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...
shrub
A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...
growing to tall by or more broad with large heads of pink or blue flowers in summer and autumn.
It is currently treated as monotypic, with no subspecies or varieties.
Common names include bigleaf hydrangea, and, for particular
cultivar group
A Group (previously cultivar-groupInternational Code of Nomenclature for Cultivated Plants, 4th edition (1969), 5th edition (1980) and 6th edition (1995)) is a formal category in the '' International Code of Nomenclature for Cultivated Plants'' (' ...
s, the names lacecap hydrangea, mophead hydrangea, and hortensia.
It is widely cultivated in many parts of the world in many climates. It is not to be confused with ''
H. aspera'' 'Macrophylla'.
Distribution and habitat
''Hydrangea macrophylla'' is endemic to Japan,
where it occurs in coastal habitats from Honshu southwards.
Natural wild plants, formerly sometimes distinguished as ''H. macrophylla'' var. ''normalis'' E.H.Wilson,
have "lacecap" structure flowerheads, with a few large sterile showy bract-like flowers that act as targets for pollinators, surrounding a central cluster of small fertile flowers. A closely related hydrangea from the mountains of the interior of Japan, ''
Hydrangea serrata'', was treated as a variety of ''H. macrophylla'' by some authors in the past,
but is currently treated as a separate species.
The species is
naturalised
Naturalization (or naturalisation) is the legal act or process by which a non-national of a country acquires the nationality of that country after birth. The definition of naturalization by the International Organization for Migration of the ...
in China, Korea, Siberia, New Zealand and the Americas, and has become an
invasive species
An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
in the
Azores
The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...
and
Madeira
Madeira ( ; ), officially the Autonomous Region of Madeira (), is an autonomous Regions of Portugal, autonomous region of Portugal. It is an archipelago situated in the North Atlantic Ocean, in the region of Macaronesia, just under north of ...
archipelagos.
Description
The term ''macrophylla'' means 'large- or long-leaved'.
The opposite leaves can grow to in length. They are simple, membranous, orbicular to elliptic and acuminate. They are generally serrated.
The natural
inflorescence
In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...
of wild ''Hydrangea macrophylla'' is a
corymb
Corymb is a botanical term for an inflorescence with the flowers growing in such a fashion that the outermost are borne on longer pedicels than the inner, bringing all flowers up to a common level. A corymb has a flattish top with a superficial re ...
, with all flowers placed in a plane. Two distinct types of flowers are found; numerous central, small, fertile
pentamerous ones, and a few peripheral, large,
tetramerous Merosity (from the greek "méros," which means "having parts")) refers to the number of component parts in a distinct whorl of a plant structure. The term is most commonly used in the context of a flower where it refers to the number of sepals in a ...
ones; the latter are usually sterile, and whitish to pale blue or pinkish.
The small flowers have five small greenish sepals and five small petals. Flowering begins in early summer and lasts until early winter. The fruit is a subglobose capsule.
In cultivation as an
ornamental plant
Ornamental plants or ''garden plants'' are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars th ...
, numerous variants have been developed as
cultivar
A cultivar is a kind of Horticulture, cultivated plant that people have selected for desired phenotypic trait, traits and which retains those traits when Plant propagation, propagated. Methods used to propagate cultivars include division, root a ...
s; in most of these (over 500 cultivars), the small central flowers replaced by large, sterile or mostly sterile tetramerous flowers, the inflorescence forming a hemisphere or a whole sphere rather than in a flat plane. These cultivar groups are known as "mophead" or "hortensia" hydrangeas.
These large flowers have colours ranging from pale pink to red, fuchsia, purple, to blue. A much smaller cultivar group (over 20 cultivars), known as "lacecap" hydrangeas, retain the natural form of flat flowerheads with small flowers surrounded by a halo of large sterile flowers, but varying from the wild plants in more intense colours.
Some cultivars (possibly many, and particularly those selected for greater cold tolerance) derive from
hybrids between ''Hydrangea macrophylla'' and ''
Hydrangea serrata'', the hill hydrangea of the mountains of Japan.
Colour and soil acidity
The flowers of ''Hydrangea macrophylla'' cultivars can be blue, red, pink, light purple, or dark purple. The colour is affected by
soil pH
Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the neg ...
. An acidic soil (pH below 7) will usually produce a flower colour closer to blue, whereas an alkaline soil (pH above 7) will produce flowers of a pink, or even a red colour. This is caused by a colour change of the
flower pigment
A biological pigment, also known simply as a pigment or biochrome, is a substance produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments. Many biol ...
s in the presence of
aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
ions which can be taken up into
hyperaccumulating plants. Scientists do not understand why this happens, whether it is due to predation or to attract pollinators.
Chemistry
Phyllodulcin,
hydrangenol, and their 8-O-glucosides, and
thunberginols A and
F can be found in ''H. macrophylla''.
Thunberginol B, the dihydroisocoumarins
thunberginol C,
D and
E, the dihydroisocoumarin glycosides
thunberginol G 3'-O-glucoside and (−)-
hydrangenol 4'-O-glucoside and four
kaempferol
Kaempferol (3,4′,5,7-tetrahydroxyflavone) is a natural flavonol, a type of flavonoid, found in a variety of plants and plant-derived foods including kale, beans, tea, spinach, and broccoli. It is also found in propolis extracts. Kaempferol i ...
and
quercetin
Quercetin is a plant flavonol from the flavonoid group of polyphenols. It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and kale are common foods containing appreciable amounts of it. It has a bitter flavor ...
oligoglycosides can be found in ''Hydrangeae Dulcis Folium'', the processed leaves of ''H. macrophylla'' var. ''thunbergii''. The leaves also contain the stilbenoid
hydrangeic acid.
The various colours, such as red, mauve, purple, violet and blue, in ''H. macrophylla'' are developed from one simple anthocyanin, delphinidin 3-glucoside (
myrtillin), which forms complexes with metal ions called
metalloanthocyanins.
Lunularic acid,
lunularin,
3,4′-dihydroxystilbene and a glycoside of lunularic acid have been found in the roots of ''H. macrophylla''.
Hydrangine is another name for the coumarin umbelliferone, and may be responsible for the possible toxicity of the plant.
Uses
Amacha is a Japanese beverage made from fermented leaves of ''Hydrangea macrophylla'' var. ''thunbergii''.
''Hydrangeae Dulcis Folium'' is a drug made from the fermented and dried leaves of ''H. macrophylla var. thunbergii'' with possible antiallergic and antimicrobial properties. It also has a hepatoprotective activity by suppression of D-galactosamine-induced liver injury in vitro and in vivo.
''Hydrangea macrophylla'' is included in the
Tasmania
Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...
n Fire Service's list of low
flammability
A combustible material is a material that can burn (i.e., sustain a flame) in air under certain conditions. A material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort a ...
plants, indicating that it is suitable for growing within a building protection zone.
Leaf extracts of ''Hydrangea macrophylla'' are being investigated as a possible source of new chemical compounds with antimalarial activity.
Hydrangeic acid from the leaves is being investigated as a possible anti-diabetic drug as it significantly lowered blood glucose, triglyceride, and free fatty acid levels in laboratory animals.
Cultivars
The two main groups of ''H. macrophylla'' cultivars are called "lacecap" and "mophead".
Some popular hydrangea
cultivars
A cultivar is a kind of cultivated plant that people have selected for desired traits and which retains those traits when propagated. Methods used to propagate cultivars include division, root and stem cuttings, offsets, grafting, tissue cult ...
(those marked have gained the
Royal Horticultural Society
The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity.
The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr ...
's
Award of Garden Merit
The Award of Garden Merit (AGM) is a long-established award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions.
It includes the full range of cultivated p ...
) include:
*'All Summer Beauty'; cold-hardy,