hydrangea(redirected from Ajisai)
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a plant genus of the family Hydrangeaceae. It includes mostly deciduous shrubs and some treelike lianas and small trees. The leaves are opposite or arranged verticillately in threes and have dentate edges. The flowers are clustered in cymes or panicles. The marginal flowers, and sometimes all the flowers of the cluster, are sterile and have four to five large white, blue, or pink sepals. The fertile flowers are often unattractive. The fruit is a pod. There are about 80 species in South and North America and in East and Southeast Asia. Two species are found in the USSR. Several species of Hydrangea are used extensively in horticulture under that name (gortenziia in the USSR).
the name used in decorative horticulture for the cultivated species of the genus Hydrangea. The most popular species is garden hydrangea (Hydrangea macrophyl-la, formerly H. hortensis), a native of Japan that was introduced into culture at the end of the 18th century. In this species the flowers are mostly corymbiform inflorescences in the center of which are small bisexual flowers. with large asexual flowers with extremely accreted sepals around the edges. There are varieties with raspberry-colored, pink, light blue, and white flowers. They are grown in greenhouses and in homes as house plants. Garden hydrangeas reproduce by means of green cuttings. The cuttings root in baskets at temperatures of 16°-18° C and then they are kept in greenhouses. In April the plants begin to flower. Outdoors. garden hydrangea is successfully grown if it is well sheltered by soil or leaves during the winter.
Sometimes panicled hydrangea (H. paniculata) is grown in greenhouses or outdoors. It is a shrub with large elongated greenish-white inflorescences that turn pink as they finish blooming. They are especially effective bole specimens and are good for growing in tubs. as well. Panicled hydrangeas propagate by cuttings and by layering. Shaggy hydrangea (H. heteromalla, formerly H. Bretschneideri) is a large shrub with many flat or corymbiform inflorescences. It is grown in the same manner as panicled hydrangea. Shrubby hydrangea (H. arborescens) is an upright shrub with broad ovate leaves and abundant round, white flower clusters. There is a garden form of shrubby hydrangea with very large clusters of sterile flowers.