HOLLYHOCK, Althaea rosea, a perennial plant of the family Malvaceae, a native of China, which has been cultivated in Great Britain for about three centuries and long since widely grown in America. The ordinary hollyhock is single-blossomed, but the florists' varieties have all double flowers, of white, yellow, rose, purple, violet and other tints, some being almost black. The plant is in its prime about August, but by careful management samples may be obtained in blossom from July to as late as November. Hollyhocks are propagated from seed, or by division of the root, or by planting out in rich sandy soil, in a close frame, with a gentle bottom heat, single eyes from woodshoots, or cuttings from out growths of the old stock or of the lateral offsets of the spike. The seed may be sown in October under cover, the plants obtained be ing potted in November, and kept under glass till the following April, or, if it be late-gathered, in May or June, in the open ground, whence, if required, the plants are best removed in October or April. In many gardens, when the plants are not dis turbed, self-sown seedlings come up in abundance about April and May. Seedlings may also be raised in February or March, by the aid of a gentle heat, in a light and rich moist soil ; they should not be watered till they have made their second leaves, and when large enough for handling should be pricked off in a cold frame; they are subsequently transferred to the flower-bed. Hollyhocks thrive best in a well-trenched and manured sandy loam. The plant is susceptible of great modification under cultivation. The forms now grown are due to the careful selection and crossing of var ieties. It is found that the most diverse varieties may be raised with certainty from plants growing near together.
The young shoots of the hollyhock are very liable to the attacks of slugs, and to a disease occasioned by a fungus, Puccinia mal vacearum, which is a native of Chile and attained notoriety in the Australian colonies, and finally, reaching Europe in 1869, threat ened the extermination of the hollyhock, the soft parts of the leaves of which it destroys, leaving the veins only remaining. It has been found especially hurtful to the plant in dry seasons. It is also parasitic on the wild mallows. The disease appears on the leaves as minute hard pale-brown pustules, filled with spores which germinate without a resting-period, but when produced late in the season may last as resting-spores until next spring. In hot dry seasons, red-spider injures the foliage very much, but may be kept at bay by syringing the plants frequently with plenty of water.