HYDRANGEA, a popular flower much in request for the decoration of conservatories during the late summer season, many thousands being annually produced for the London market. The plant to which the name is most commonly applied is the Hydrangea Hortensia, a low deciduous shrub, producing rather large oval strongly-veined leaves in opposite pairs along the stem. It is terminated by a massive globular corymbose head of flowers, which remain a long period in an ornamental condition. The nor-mal colour of the flowers, the majority of which have neither stamens nor pistil, is pink; but by the influence of sundry agents in the soil, such as alum or iron, they become changed to blue. The part of the inflorescence which appears to be the flower is an exaggerated expansion of the calyx-leaves, the other parts being generally abortive. The perfect flowers are small, rarely produced in the species above referred to, but well illustrated by others, in which they occupy the inner parts of the corymb, the larger showy neuter flowers being produced at the circumference. A pure white variety, named Thomas Hogg, has been recently introduced, and is a very desirable plant.
There are upwards of thirty species, found chiefly in Japan, in the mountains of India, and in North America, and many of them are familiar in gardens. H. Hortensia is the most useful for decoration, as the head of flowers lasts long in a fresh state, and by the aid of forcing can behad for a considerable period for the ornamentation of the greenhouse and conservatory. Their natural flowering season is towards the end of the summer, but they may be had earlier by means of forcing. H. japónica is another fine conservatory plant, with foliage and habit much resembling the last-named, but this has flat corymbs of flowers, the central ones small and perfect, and the outer ones only enlarged and neuter. This also produces pink or blue flowers under the influence of different soils.
The Japanese species of hydrangea are sufficiently hardy to grow in any tolerably favourable situation, but except in the most sheltered localities they seldom blossom to any degree of perfection in the open air, the head of blossom depending on the uninjured development of a well-ripened terminal bud, and this growth being frequently affected by late spring frosts. They are much more useful for pot-culture indoors, and should be reared from cuttings of j shoots having the terminal bud plump and prominent, put i in during summer, these developing a single head of flowers the succeeding summer. Somewhat larger plants may be had by nipping out the terminal bud and inducing three or four shoots to start in its place, and these, being steadily developed and well-ripened, should each yield its inflor-escence in the following summer, that is, when two years old. Large plants grown in tubs and vases are fine subjects for large conservatories, and may be used for decorating terrace walks and similar places during summer, being housed in winter, and started under glass in spring.
The Indian and American species, especially the latter, are quite hardy, and some of them are extremely effective. The finest of these by far is the Hydrangea paniculata grandijiora, the branched inflorescence of which is under favourable circumstances a yard or more in length, and consists of large spreading masses of crowded whits neuter flowers which completely conceal the few inconspicuous fertile ones. The plant attains a height of 8 to 10 feet, and when in flower late in summer and in autumn is a very attractive object in the shrubbery.