Hydrangea (Hydrangea or Hortensia) is a genus comprising 70 - 75 species of flowering plants in family Hydrangeaceae, native to southern and eastern Asia, North and South America. The biggest species diversity happens in eastern Asia, in China, Korea, and Japan.
Hydrangea species are mostly shrubs, but some are small trees and others lianas which can grow up to 30 m by climbing up trees. They can also be deciduous or evergreen, and the species that grown in temperate regions are all deciduous. There are two flower arrangements in some Hydrangeas species called mophead and lacecap. Mophead flowers are the large, round flowerheads, while lacecap flowers bear flowers that are round, flat with a center core of subdued, fertile flowers surrounded by rings of showy, sterile flowers. Other species have all the flowers fertile and of the same size. Hydrangea flowers are produced at the ends of stems and bloom from early spring to late autumn.
Most species of Hydrangea have white flowers but in some species (notably H. macrophylla), the flowers can come in blue, red, pink, light purple or dark purple color. In these species, the color of the flowers are often reflect the pH of the soil they were grown in. Acidic soils produce blue flowers, neutral soils produce very pale cream petals, and alkaline soil have flowers that are pink or purple color. This is caused by a color change of the flower pigments in the presence of aluminium ions.
Hydrangea macrophylla ( Bigleaf Hydrangea, French Hydrangea, Lacecap Hydrangea, Mophead Hydrangea, Penny Mac and Hortensia) is a species of Hydrangea native to Japan. It is widely available and used as ornamental plants in mixed borders, in woodland gardens and in containers. The flowers are either blue or pink, depending on the pH of the soil. Its rich foliage and large size make it a wonderful background for white or light colored flowers. In warm climates, the plant is good for adding a splash of spring time color to shady areas and woodland gardens. This species is easy to grow and needs little attention except for the removal of old flower heads.
Hydrangea aspera, 3m high and across, is an upright deciduous shrub, native to the regions between the Himalaya, across southern China, to Taiwan. It bears flattened flower heads in summer and autumn and are in various shades of pale blue. Plants in the Villosa Group, 1.2 m high and across, bears pink-purple or bluish-purple flowers and do best in slightly acidic soil.
Hydrangea paniculata (Panicled Hydrangea) is an upright shrub which can grow up to 7 m tall. It responds well to pruning and is grown for its large, conical, cream-white flower heads. This species is found in eastern Chian, Korea, Japan, and Sakhalin.
Hydrangea grows well in sun or partial shade, in moisture-retentive but well-drained soil. Propagation is by softwood cuttings in summer, hardwood cuttings in winter. Diseases are honey fungus and leaf spot.
A very large Hydrangea at Watermouth Castle, north Devon, England. http://commons.wikimedia.org/wiki/File:Hydrangea.watermouth.arp.750pix.jpg Arpingstone
Hydrangea http://commons.wikimedia.org/wiki/File:Hortensias.JPG Christian Pinatel
http://commons.wikimedia.org/wiki/File:Hydrangea_aspera_Macrophylla1UME.JPG
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