This section is from the book "The Gardener V3", 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.
Any one who has a stock of Hollyhocks should now propagate as many as he can. If the old stock plants had been lifted in the early part of winter, potted and placed where a little growth has been made since, they will, during the beginning of this month, be in the proper condition to manufacture into plants by root-grafting. The way to do this is to get some healthy Hollyhock roots, preferring those with growing rootlets, and cut up as many as are required. Then take off the offsets with as much stem as can be got; prepare these first by cutting the stem half through, and slit the stem up, removing the half of it up to the cross-cut; then select a root of as near as possible the same thickness, and cut it to fit into the stem of the graft. Run a pin through the two, and a strand of matting round them, and pot into 4-inch pots. When all are grafted the pots should be plunged in a mild bottom-heat, and the plants kept moderately airy and not over warm. These make good plants for putting out in April with those propagated the preceding autumn. The other modes of propagating named sorts are by cuttings from near the root, through the summer, and by cutting the partially hardened stem into single eyes, and inserting them in boxes or frames in sandy soil.
Both cuttings and eyes should be kept as cool as possible, under which conditions they produce good plants before winter. The Hollyhock comes very true to character from seed. The best time to sow is about the beginning of September, in a cold frame, where they should remain throughout the winter. Plants from earlier-sown seeds make too much growth, and do not come through the winter so well. The Hollyhock cannot get too deep a soil, or one too rich for its wants, in order to obtain strong spikes and large blooms. Deep and rich soils carry the plants through spells of hot weather without needing to have recourse to the watering-pot every other day, and in all cases amply repay the work and manure laid out on them. In such soils the plants ought to be planted not closer than four feet from each other, - more if space can be spared. Hollyhocks do well and look well in mixed borders, and here more room can be allowed them than when grown together in beds. Long and strong stakes are necessary early in summer; but in tying take care that the ties are not so tight as to cut the fast-thickening stems. Spikes intended for exhibiting should have the tops pinched out, and the blooms, where too thickly set, thinned out. Shading must also be provided.
This is economically and efficiently provided by swathing the spikes in newspapers - of course, providing means of keeping the papers off the blooms.
Last year there were plants offered for sale reputed to be free from the Hollyhock disease, and many more than usual were grown throughout the country. In some localities it seems, from information I have received, that the plants did well and kept free from the fungus - at least to an extent that was not noticeable. In my own case, I bought from a source warranted perfectly "clean;" but on one or two of the plants I found the fungus. The infected leaves were removed, and I determined to try and stamp out the fungus if it was simply confined to these plants. As growth proceeded the few specimens which appeared were removed by cutting them out of the leaf and burning. This did very well for a time, until the fungus appeared in hundreds on stems as well as leaves. Then the plants were cut down underneath the soil right into the root-stock. The shoots which broke were very soon in a like condition with those which were removed, and they were again cut over in the same way. The plants had only time to commence a fresh growth before winter when the plants were lifted for spring propagation. Clean off-growths propagated in summer went exactly the same way as the parent stocks.
Curiously enough, in one locality where the Hollyhock has done well during the past year, the common Mallows by the waysides were covered with the fungus. The question is altogether a puzzling one - why, in some districts, the fungus should attack the plants, and in another, where the fungus was most abundant, the plants should escape. It has been noted before how curious it is that the common Mallow should live and perform its functions under a crop of the parasite which kills the Hollyhock; but in the Mallow the leaf alone appears to be subject to attack, while in the Hollyhock, not only the leaves but the stems are affected. If the stems were not subjected to attack, it is probable the fungus would not prove of such a deadly character as it is. Should we now be in for a few years of really fine summers, it will be seen whether the Hollyhock will not again go under, as it is only during the last few years that any progress seems to have been made in getting up healthy stocks.
R. P. B.