This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
It must by no means be assumed, that because comparatively little is now written about the Hollyhock, its area of cultivation has in consequence become considerably reduced. It is still a flower much grown, and long may it continue to be grown, for its rich beauty and its great usefulness as a decorative agent. As one who has cultivated the Hollyhock for many years past, I may be permitted to put forward a plea in its favour in the pages of the 'Gardener.'
My custom is to pot up the ground roots of the Hollyhocks - i.e., those from which I have taken my exhibition flowers during the summer - in November, using pots according to the size of the roots, and generally employing the sizes thirty-twos and twenty-fours: these I find quite large enough for the greater part of the roots. They are first duly trimmed, and then potted firmly in a light sandy soil, and if not naturally sandy, I mingle with it a good portion of road-grit, with the addition of some leaf-soil. When potted, they have the protection of a greenhouse pit, and are kept rather dry during the winter months, as they are impatient of much moisture round the collar of the plant, and many a good variety has been lost from this cause.
Death from excessive moisture is often the lot of the plants allowed to remain in the open ground all the winter. Their existence is materially aided by placing either sand or cinder-ashes round the neck of the plants to protect them from wet, as well as insects and slugs, the last-named being a dreaded enemy of the Hollyhock - so much so, that it is often necessary to give the plants a dusting of slacked lime in damp weather. I commence the process of propagation by the middle of February or the beginning of March, as at this season of the year cuttings made from the young growth from the plants root readily. I take them off about 4 inches long, and place several in 32-sized pots, using a soil similar to that I should employ for striking cuttings of bedding Pelargoniums. I press them firmly into the soil, and then well water them, so as to thoroughly saturate the soil; they will then require but little water afterwards, until they are rooted. I place the cutting pots in a temperature of from 65° to 75°, and if some bottom-heat can be employed, so much the better.
Should some of the larger leaves suffer from damp, a pair of scissors will soon remove them.
I often avail myself of the propagating season to raise some seedlings, when I have at command such a temperature as that stated above. Using a light sandy compost, I sow the seed very thickly in pots or seed-pans, and as soon as large enough to handle, I pot them singly into small 60-pots about the time I do the cuttings, for I use the same-sized pots for each. As soon as the pots are filled with roots, both cuttings and seedlings, I shift into 32-pots, and if the plants are kept growing till the middle of April, they can be gradually hardened off preparatory to being planted in the open air, and both seedlings and cuttings will bloom the same season.
The work of preparing the ground for the reception of the plants is an important matter. The situation I select as an exhibitor is a spot quite remote from the shade of trees, or the reach of their roots, and where the plants can have the full benefit of the sun. The ground should be well trenched previously, at least 2 feet deep, and plenty of rotten dung worked in as the work proceeds: dung from an old cucumber-bed will be found very suitable for the purpose.
I select a fine day for planting out, when the soil is in good working order. The plants are placed in rows fully 5 feet apart, the plants 4 feet apart in the row. As soon as the plants are 1 foot in height, they are staked, the stake being driven firmly into the ground, and the plant secured to it by pieces of matting, not too tightly, so that there is perfect freedom of expansion. As the plants increase in size I employ strong twine for tying out, as a security against winds. At this stage it is highly important that the plants be kept growing freely, and plenty of water is given in hot and dry weather, and copious sprinklings overhead from a rose watering-pot. If I cannot get rainwater, I always expose it to the influence of the sun before using it.
Red-spider often causes the cultivator some trouble. I cut off all leaves infested by it and bury them, and mulch the plants well with fresh rotten dung, and give a copious soaking of manure-water once a-week. The exhibitor should allow but one spike of flowers to each plant, and in the case of cut flowers being required, they should be thinned out so as not to interfere with each other. This is best done with a pair of strong scissors.
Well and truly has the Hollyhock been termed "a noble flower." For garden decoration it is in some respects unapproachable, yielding such fine masses of gay-coloured flowers. It can be planted in various ways - one especially, that as a back row to a broad ribbon-border. I have used it in several ways in the flower-garden, and always with the best effect, and am of opinion that such a garden is not comparatively perfect even without it. I hope to give some hints shortly on the use of the Hollyhock as a decorative agent in the flower-garden.
William Plester. Elsenham Hall Gardens.