1911 Encyclopædia Britannica/Hollyhock

HOLLYHOCK (from M.E. holi—doubtless because brought from the Holy Land, where it is indigenous (Wedg.)—and A.-S. hoc, a mallow), Althaea rosea, a perennial plant of the natural order Malvaceae, a native of the East, which has been cultivated in Great Britain for about three centuries. 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 examples 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 outgrowths of the old stock or of the lateral offsets of the spike. The seed may be sown in October under cover, the plants obtained being 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 disturbed, 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 spikes as they grow must be staked; and water and, for the finest blossoms, liquid manure should be liberally supplied to the roots. Plants for exhibition require the side growths to be pinched out; and it is recommended, in cold, bleak or northerly localities, when the flowering is over, and the stalks have been cut off 4 to 6 in. above the soil, to earth up the crowns with sand. Some of the finest double-flowered kinds of hollyhock do not bloom well in Scotland. The plant is susceptible of great modification under cultivation. The forms now grown are due to the careful selection and crossing of varieties. 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 malvacearum, which is a native of Chile, attained notoriety in the Australian colonies, and finally, reaching Europe in 1869, threatened the extermination of the hollyhock, the soft parts of the leaves of which it destroys, leaving the venation 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. Spraying early in the season with Bordeaux mixture is an effective preventive, but the best means of treatment is to destroy all leaves as soon as they show signs of being attacked, and to prevent the growth of other host-plants such as mallows, in the neighbourhood. 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 clean water.