Hydrangea

Hydrangea macrophylla
Scientific classification
Kingdom:	Plantae
Unranked:	Angiosperms
Unranked:	Eudicots
Unranked:	Asterids
Order:	Cornales
Family:	Hydrangeaceae
Genus:	Hydrangea L.
Species
See text

Hydrangea (; common names Hydrangea and Hortensia) is a genus of about 70 to 75 species of flowering plants native to southern and eastern Asia (China, Japan, Korea, the Himalayas, and Indonesia) and North and South America. By far the greatest species diversity is in eastern Asia, notably China, Japan, and Korea. Most are shrubs 1 to 3 meters tall, but some are small trees, and others lianas reaching up to 30 metres by climbing up trees. They can be either deciduous or evergreen, though the widely cultivated temperate species are all deciduous.

Having been introduced to the Azores Islands of Portugal, they are now very common there, particularly on Faial Island, which is known as the "blue island" due to the vast number of hydrangeas present on the island, and on Flores Island.

Species in the related genus Schizophragma, also in Hydrangeaceae, are also often known as hydrangeas. Schizophragma hydrangeoides and Hydrangea petiolaris are both commonly known as climbing hydrangeas.

There are two flower arrangements in hydrangeas. 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, fertile flowers surrounded by outer rings of showy, sterile flowers.

Life cycle

Hydrangea flowers are produced from early spring to late autumn; they grow in flowerheads (corymbs or panicles) at the ends of the stems. In many species, the flowerheads contain two types of flowers, small fertile flowers in the middle of the flowerhead, and large, sterile bract-like flowers in a ring around the edge of each flowerhead. Other species have all the flowers sterile and of the same size.

Colours and acidity

In most species the flowers are white, but in some species (notably H. macrophylla), can be blue, red, pink, light purple, or dark purple. In these species the exact colour often mirrors the pH of the soil; acidic soils produce blue flowers, neutral soils produce very pale cream petals, and alkaline soils results in pink or purple. This is caused by a color change of the flower pigments in the presence of aluminium ions which can be taken up into hyperaccumulating plants.

Partial list of species

• Hydrangea anomala (Climbing Hydrangea). Himalaya, southwest Mainland China.
• Hydrangea arborescens (Smooth Hydrangea). Eastern North America.
• Hydrangea aspera. Mainland China, Himalaya.
• Hydrangea bretschneideri. Mainland China.
• Hydrangea candida. Mainland China.
• Hydrangea caudatifolia. Mainland China.
• Hydrangea chinensis. Mainland China.
• Hydrangea chungii. Mainland China.
• Hydrangea cinerea (Ashy Hydrangea). Eastern United States.
• Hydrangea coacta. Mainland China.
• Hydrangea coenobialis. Mainland China.
• Hydrangea davidii. Mainland China.
• Hydrangea dumicola. Mainland China.
• Hydrangea gracilis. Mainland China.
• Hydrangea heteromalla. Himalaya, west and north Mainland China.
• Hydrangea hirta. Japan.
• Hydrangea hypoglauca. Mainland China.
• Hydrangea integrifolia. Mainland China.
• Hydrangea involucrata. Japan, Taiwan.
• Hydrangea kawakamii. Taiwan.
• Hydrangea kwangsiensis. Mainland China.
• Hydrangea kwangtungensis. Mainland China.
• Hydrangea lingii. Mainland China.
• Hydrangea linkweiensis. Mainland China.
• Hydrangea longifolia. Mainland China.
• Hydrangea longipes. Western China.
• Hydrangea macrocarpa. Mainland China.
• Hydrangea macrophylla (Bigleaf Hydrangea). Southeast Japan.
• Hydrangea mangshanensis. Mainland China.
• Hydrangea paniculata (Panicled Hydrangea). Eastern Mainland China, Japan, Korea, Sakhalin.
• Hydrangea petiolaris (Climbing Hydrangea). Japan, Korea, Sakhalin.
• Hydrangea quercifolia (Oakleaf Hydrangea). Southeast United States.
• Hydrangea radiata (Silverleaf Hydrangea). Southeast United States.
• Hydrangea robusta. Mainland China, Himalaya.
• Hydrangea sargentiana. Western Mainland China.
• Hydrangea scandens. Southern Japan south to the Philippines.
• Hydrangea serrata. Japan, Korea.
• Hydrangea serratifolia. Chile, western Argentina.
• Hydrangea stenophylla. Mainland China.
• Hydrangea strigosa. Mainland China.
• Hydrangea stylosa. Mainland China.
• Hydrangea sungpanensis. Mainland China.
• Hydrangea xanthoneura. Mainland China.
• Hydrangea zhewanensis. Mainland China.

Cultivation and uses

Hydrangeas are popular ornamental plants, grown for their large flowerheads, with Hydrangea macrophylla being by far the most widely grown with over 600 named cultivars, many selected to have only large sterile flowers in the flowerheads. 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. Due to their attractive flowers, Hydrangeas are widely used in contemporary interior decoration.

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.

In Japan, ama-cha, 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. Ama-cha is poured over a statue of Buddha in the ceremony 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:Template:Linktext) is used for a herbal tea called sugukcha (수국차) or ilsulcha (이슬차).

Gallery

Wild hydrangea var annabelle.jpg

Wild Hydrangea v. Annabelle
Hydrangea arborescens

Diseases

Main article: List of hydrangea diseases

References

¹ http://www.erowid.org/herbs/hydrangea/hydrangea.shtml

External links

• www.hydrangeaworld.com
• Flora of China: Hydrangea
• Flora of Nepal: Hydrangea species list
• USDA Plant Profile: Hydrangea
• Hydrangea - their pruning and care
• Hydrangea - selecting shrubs (University of Illinois Extension)
• Hydrangea species and hybrids
• Propagating Hydrangeas
• Red Listing of Threatened Hydrangeas The Global Trees Campaign of BGCI, Fauna & Flora International (FFI) and the UNEP World Conservation Monitoring Centre (UNEP-WCMC)