Hydrangea

''Hydrangea'', () commonly named the hortensia, is a genus of over 75 species of flowering plants native to Asia and the Americas. By far the greatest species diversity is in eastern Asia, notably China, Korea, and Japan. Most are shrubs tall, but some are small trees, and others lianas reaching up to by climbing up trees. They can be either deciduous or evergreen, though the widely cultivated temperate species are all deciduous.

''Hydrangea'' is derived from Greek and means ‘water vessel’ (from ''húdōr'' "water" + ''ángos'' or ''angeîon'' "vessel"), in reference to the shape of its seed capsules. The earlier name, ''Hortensia'', is a Latinised version of the French given name Hortense, honoring French astronomer and mathematician Nicole-Reine Hortense Lepaute. This claim is disputed in page 88 on citation 10 at Nicole-Reine Hortense Lepaute page, which says: "Larousse considers this an injustice, and remarks that it has led many persons to the erroneous notion that "Hortensia" was one of her names; it was probably only the Latin adjective from "hortus." The flowers of hydrangea act as natural pH indicators, sporting blue flowers when the soil is acidic and pink when the soil is alkaline.

Life cycle

''Hydrangea'' flowers are produced from early spring to late autumn; they grow in flowerheads (corymbs or panicles) most often at the ends of the stems. Typically the flowerheads contain two types of flowers: small non-showy fertile flowers in the center or interior of the flowerhead, and large, sterile showy flowers with large colorful sepals (tepals). These showy flowers are often extended in a ring, or to the exterior of the small flowers. Plants in wild populations typically have few to none of the showy flowers, while cultivated hydrangeas have been bred and selected to have more of the larger type flowers.

There are two flower arrangements in hydrangeas with corymb style inflorescences, which includes the commonly grown "bigleaf hydrangea"—''Hydrangea macrophylla''. Mophead flowers are large round flowerheads resembling pom-poms or, as the name implies, the head of a mop. In contrast, lacecap flowers bear round, flat flowerheads with a center core of subdued, small flowers surrounded by outer rings of larger flowers having showy sepals or tepals. The flowers of some rhododendrons and viburnums can appear, at first glance, similar to those of some hydrangeas.

Hydrangea flowers, when cut, dehydrate easily and wilt very quickly due to the large surface area of the petals. A wilted hydrangea may have its hydration restored by first having its stem immersed in boiling water; as the petals of the hydrangea can also absorb water, the petals may then be immersed, in room-temperature water, to restore the flower's hydration.

Colors and soil acidity

In most species, the flowers are white, but in others (notably ''H. macrophylla''), they can be blue, red, pink, light purple, or dark purple. In these species, floral color change occurs due to the presence of aluminum ions which are available or tied up depending upon the soil pH. For ''H. macrophylla'' and ''H. serrata'' cultivars, the flower color can be determined by the relative acidity of the soil: an acidic soil (pH below 7), will have available aluminum ions and typically produce flowers that are blue to purple, whereas an alkaline soil (pH above 7) will tie up aluminum ions and result in pink or red flowers. This is caused by a color change of the flower pigments in the presence of aluminum ions which can be taken up into hyperaccumulating plants. Lowering the pH of potting soils or mixes usually does not change the flower color to blue, because these soils have no aluminum ions. The ability to blue or pink a hydrangea is also influenced by the cultivar. Some plants are selected for their ability to be blued, while others are bred and selected to be red, pink, or white. The flower color of most other Hydrangea species is not affected by aluminum and cannot be changed or shifted. Hydrangeas are also nicknamed 'Change Rose'.

Partial list of species

*''Hydrangea anomala'' – (climbing hydrangea) Himalaya, southwest China
*'' Hydrangea arborescens'' – (smooth hydrangea) eastern North America
*'' Hydrangea aspera'' – China, Himalaya
*''Hydrangea bretschneideri'' – China
*''Hydrangea chinensis'' – China and Taiwan
*''Hydrangea chungii'' – China
*'' Hydrangea cinerea'' – (ashy hydrangea) eastern United States
*''Hydrangea coenobialis'' – China
*''Hydrangea davidii'' – China
*'' Hydrangea glaucescens'' – China, Myanmar and Vietnam
*''Hydrangea gracilis'' – China
*''Hydrangea heteromalla'' – Himalaya, west and north China
*'' Hydrangea hirta'' – Japan
*''Hydrangea hydrangeoides'' – Ulleungdo, Japan, Kurils
*''Hydrangea hypoglauca'' – China
*''Hydrangea integrifolia'' – China
*'' Hydrangea involucrata'' – Japan, Taiwan
*''Hydrangea jelskii'' – Andes
*''Hydrangea kwangsiensis'' – China
*''Hydrangea kwangtungensis'' – China
*''Hydrangea lingii'' – China
*''Hydrangea linkweiensis'' – China
*'' Hydrangea longifolia'' – China
*''Hydrangea longipes'' – western China
*''Hydrangea macrocarpa'' – China
*'' Hydrangea macrophylla'' – (bigleaf hydrangea) southeast Japan, southern China
*'' Hydrangea mangshanensis'' – China
*'' Hydrangea paniculata'' – (panicled hydrangea) eastern China, Japan, Korea, Sakhalin
*'' Hydrangea peruviana'' – Costa Rica and Panama, Andes
*'' Hydrangea petiolaris'' – (climbing hydrangea) Japan, Korea, Sakhalin
*'' Hydrangea quercifolia'' – (oakleaf hydrangea) southeast United States
*''Hydrangea radiata'' – (silverleaf hydrangea) southeast United States
*'' Hydrangea robusta'' – China, Himalaya
*'' Hydrangea sargentiana'' – western China
*''Hydrangea scandens'' – southern Japan south to the Philippines
*'' Hydrangea serrata'' – Japan, Korea
*''Hydrangea serratifolia'' – Chile, western Argentina
*''Hydrangea strigosa'' – China
*''Hydrangea stylosa'' – China
*'' Hydrangea tarapotensis'' – Andes
*'' Hydrangea xanthoneura'' – China
*''Hydrangea zhewanensis'' – China

Fossil record

''Hydrangea alaskana'' is a fossil species recovered from paleogene strata in Jaw Mountain Alaska.

Four fossil seeds of ''Hydrangea polonica'' have been extracted from borehole samples of the Middle Miocene fresh water deposits in Nowy Sacz Basin, West Carpathians, Poland.

Cultivation and uses

Hydrangeas are popular ornamental plants, grown for their large flowerheads, with '' Hydrangea macrophylla'' being by far the most widely grown. It has over 600 named cultivars, many selected to have only large sterile flowers in the flowerheads. ''Hydrangea macrophylla'', also known as bigleaf hydrangea, can be broken up into two main categories; mophead hydrangea and lacecap hydrangea. Some are best pruned on an annual basis when the new leaf buds begin to appear. If not pruned regularly, the bush will become very 'leggy', growing upwards until the weight of the stems is greater than their strength, at which point the stems will sag down to the ground and possibly break. Other species only flower on 'old wood'. Thus new wood resulting from pruning will not produce flowers until the following season.

The following cultivars and species have gained the Royal Horticultural Society's Award of Garden Merit under the synonym ''Schizophragma'':
* ''S. hydrangeoides'' var. ''concolor'' 'Moonlight'
* ''S. hydrangeoides'' var. ''hydrangeoides'' 'Roseum'
*'' S. integrifolium''

Hydrangea root and rhizome are indicated for treatment of conditions of the urinary tract in the Physicians' Desk Reference for Herbal Medicine and may have diuretic properties. Hydrangeas are moderately toxic if eaten, with all parts of the plant containing cyanogenic glycosides. '' Hydrangea paniculata'' is reportedly sometimes smoked as an intoxicant, despite the danger of illness and/or death due to the cyanide.

The flowers on a hydrangea shrub can change from blue to pink or from pink to blue from one season to the next depending on the acidity level of the soil. Adding organic materials such as coffee grounds, citrus peel or eggshells will increase acidity and turn hydrangea flowers blue, as described in an article on Gardenista.
A popular pink hydrangea called Vanilla Strawberry has been named "Top Plant" by the ''American Nursery and Landscape Association''.

The hybrid "Runaway Bride Snow White", bred by Ushio Sakazaki from Japan, was named Plant of the Year at the 2018 RHS Chelsea Flower Show.

In culture

In Japan, '' ama-cha'', 甘茶, meaning sweet tea, is another herbal tea made from '' Hydrangea serrata'', whose leaves contain a substance that develops a sweet taste ( phyllodulcin). For the fullest taste, fresh leaves are crumpled, steamed, and dried, yielding dark brown tea leaves. Ama-cha is mainly used for ''kan-butsu-e'' (the Buddha bathing ceremony) on April 8 every year—the day thought to be Buddha's birthday in Japan. During the ceremony, Ama-cha is poured over a statue of Buddha and served to people in attendance. A legend has it that on the day Buddha was born, nine dragons poured Amrita over him; ama-cha is substituted for Amrita in Japan.

In Korean tea, '' Hydrangea serrata'' (hangul:산수국 hanja:) is used for an herbal tea called ''sugukcha'' (수국차) or ''isulcha'' (이슬차).

The pink hydrangea has risen in popularity all over the world, especially in Asia. The given meaning of pink hydrangeas is popularly tied to the phrase, "You are the beat of my heart," as described by the celebrated Asian florist Tan Jun Yong, where he was quoted saying, "The light delicate blush of the petals reminds me of a beating heart, while the size could only match the heart of the sender!"

''Hydrangea quercifolia'' was declared the official state wildflower of Alabama in 1999.State Botanical SymbolsBy Alan McPherson, p.3

Hydrangeas were used by the Cherokee Indians. A mild diuretic and cathartic, it was considered a valuable remedy for removal of stone and gravel in the bladder.

Bee-friendliness

Hydrangea variants vary in bee-friendliness and their ability to feed pollinators. In general, common hydrangeas are not bee-friendly because their flowers are sterile, e.g. ''Hydrangea macrophylla hortensis'' (''mophead'') and ''H. paniculata'' (''limelight'').
Those that give food for bees and pollinators are:
* ''Hydrangea anomala petiolaris''
* ''Hydrangea arborescens'': Smooth hydrangeas are versatile and spectacular, and can be used in a variety of landscape settings, including foundation plantings, perennial gardens, hedges, cut flower gardens, naturalising, pollinator, and wildlife gardens.
* ''Hydrangea aspera'':
* ''Hydrangea mycrophylla'': Bigleaf hydrangeas are classic choices for flower gardens, cottage gardens, and seaside plantings. They can also be used for low hedges or edging, and they offer a splash of colour to foundation plantings.
* ''Hydrangea paniculata'' (''grandiflora''): Panicle hydrangeas are the most sun-tolerant and wilt-resistant of the hydrangeas. It's perfect for Specimen plantings, mixed borders, and mass plantings. It can be used as a hedge or a screen. Excellent for both fresh and dried cut flowers.
* ''Hydrangea quercifolia'': Oakleaf hydrangea blooms on old growth. It thrives in damp, well-drained environments. In colder climates, winter protection may be required. Shrub with a deciduous appearance. Apply a slow-release fertiliser formulated for trees and shrubs in the early spring.

Gallery

File:Hortensiapink.JPG, '' Hydrangea macrophylla''
File:Hydrangea close up.jpg, Hydrangea flowers close up.
File:Pink Hydrangea Flowers.jpg, Flowers
File:Hydrangea-heads-pale.png, ''Hydrangea macrophylla'', flowers.
File:Blue Hydrangea.jpg, ''Hydrangea macrophylla'', flowers
File:Hydrangea redoute.JPG, ''Hydrangea sp'' painted by the botanical artist Redouté.
File:Hydrangea quericifolia2.jpg, ''Hydrangea quercifolia''
File:Hydrangea leaves.jpg, ''Hydrangea macrophylla'', leaves
File:Wild hydrangea var annabelle.jpg, Wild Hydrangea v. Annabelle
''Hydrangea arborescens''
File:Hydrangea arborescens.jpg, Wild Hydrangea v. Annabelle
''Hydrangea arborescens''
File:Hydrangea arborescens annabelle.JPG, 8" Annabelle Hydrangea Bloom. ''Hydrangea arborescens''.
File:Hydrangea-aspera-zoo-cgn-07074-mutante.jpg, ''Hydrangea aspera ssp. sargentiana''
File:BlueHydrangea.JPG
File:Hydrangea paniculata IMG 6629.JPG, '' Hydrangea paniculata''
File:Hydranchia.JPG, Hydrangea flowers from Kerala, India
File:Hydrangeas corner.JPG, Hydrangeas in front of the Office de Tourisme Building in Chartres, France.
File:Hydrangea-08-10-08.JPG, Hydrangea flowers at the " Cerro El Avila" National Park, Venezuela.
File:Hydrangeea.jpg, Hydrangea flowers, Srinagar, Kashmir, India.
File:Hydrangea flowers in the rain.jpg, Hydrangea flowers
File:Petrópolis - Cidade das Hortências e do Russo - Nevoeiro.jpg, Hydrangea flowers in Petrópolis, Brazil.
File:Lagonegro3.jpg, Hydrangeas near the Black Lake of Gramado, southern Brazil.
File:Hydrangea-flower.jpg, Purple hydrangea flowers
File:Hydrangea arborescens leaf.jpg, Hydrangea arborescens leaf
File:Hydrangea summer garden.jpg
File:Hydrangea flower white.jpg
File:Hydrangea flower summer garden.jpg
File:Wilted hydrangea.jpg
File:Hydrangea flower 3.jpg, flower of hydrangea
File:Hydrangea flower 5.jpg, flower of hydrangea

Diseases

References

External links

erowid.orgFlora of Nepal: ''Hydrangea'' species listHydrangea – selecting shrubsHydrangea species and hybridsPropagating HydrangeasRed Listing of Threatened HydrangeasHydrangea all FAQs

{{Taxonbar, from=Q155997

Hydrangea
Cornales genera
Christmas plants
Asterid genera