The difference betweenand division is that cuttings are pieces taken from one part of the plant only, whereas division generally implies the division of a root with some active or dormant and attached to each portion. In effect it is the whole plant that is divided. In the case of a , more after-care is generally needed, until the missing parts of the plant have developed. Cuttings can be grouped under various headings, which will be described below.
Stem cuttings are the most common. The idea underlying these is that any part of a plant severed from the remainder will, in time, grow to a complete new plant if (a) it does not dry out and die, (b) the necessary food supply can be maintained, and (c) it does not decay through lack of air. To take a portion ofand keep it under water would prevent drying, but lack of air would cause decay. To set the base in water and leave the top exposed to the air sometimes means that evaporation takes place rapidly from the surfaces while the amount of water that can be absorbed through a cut stem is insufficient to make good the loss by evaporation. Thus it can be seen that a middle course must be steered between these two extremes.
The gardener solves the various difficulties in these ways : First, he either takes his cuttings in autumn, when he inserts them in the open and knows that there will be no lack of moisture during the winter, or he takes them at other seasons and keeps them under glass, where the air is kept moist and also warm. (A bell glass, or a closed frame, serves to keep the air warm.) He takes cuttings in the open air at a season when plants are taking in little or no food, so that the question of food supply does not arise. Under glass he watches the cuttings carefully, and as soon asdevelop, he allows them a slightly richer in which to find their food supply. Finally —though he keeps his cuttings and the air moist—he uses either pure sand or a very sandy , which allows air to filter through to the roots and that are underground. The use of sand is necessary for cuttings both in the open and under glass, and is perhaps the most important point in connection with them.
Soft cuttings root fairly easily so long as they can be kept sufficiently close and warm. Pure sand is probably the safest medium, and a propagating frame is advisable. Such cuttings are generally small side growths, taken off as soon as they have made perhaps three or four pairs of leaves. The lowest leaves are removed, to allow a clean piece of stem to enter the sand. The actual cut is made just below a joint, or, if convenient, themay be pulled from the parent plant with a downward jerk, so that it comes away with a “heel.”
The cuttings can be inserted close together, made as firm as possible, and watered lightly overhead before the glass is set over them. Shading from brilliant sunshine is necessary, and the cuttings should be examined daily and surplus water that collects on the glass should be wiped away. Immediately new growth is apparent, the cuttings may be potted up singly in thumb, and grown normally.
Soft cuttings can be rooted in summer in a shady part of the open garden, if they are kept moist overhead; but there is always some risk in this if the summer is dry, and it is really safer to use glass.
Taking Cuttings Of Hard Wood Plants
Hard wood cuttings, that is, cuttings of shrubs and trees, are generally taken in the autumn, and when hardy subjects are being increased, these cuttings are usually inserted in the open ground. Preparation of the nursery bed for them consists in thorough digging and cleaning, and the use of sufficient sand to make an open porous compost all over the bed. In the case of a bed on stiff clay, a 2-in. Dressing of sand over the whole surface before any cuttings are inserted is useful. Some of this will trickle into the holes made or the cuttings, and will help to avoid decay.
Wood most suitable for cuttings is that of one season’s growth, but well ripened in the sun, not soft and sappy. Pieces vary in length according to the kind of plant, but generally a piece with half a dozen joints to it is good enough. The cut is made just below a joint, and the bottom leaves (if present) are removed to allow a clean stem to enter the soil. From one-third to one-half should enter the soil, which must be made quite firm. An old garden rule is to “lay the cuttings over towards the north “; but it is not certain that this method is any better than leaving the cuttings in an upright.
There are a few plants which require special treatment, but these the gardener will quickly discover for himself. Cuttings of clematis, for instance, root most readily if cuts are made midway between the joints or “nodes,” and there are a few other shrubs that favour inter-nodal cuttings.
Some shrubs have, in the past, been particularly difficult to root from cuttings, but a modern discovery has made success with these much more certain. This discovery is commercialized in the form of “ Hormone A,” a substance which can be bought from any horticultural sundriesman. Cuttings are soaked in a solution of the chemical, and after such treatment they root more rapidly, and make stronger root systems.
It is not a practical proposition to use this treatment for all cuttings, but when “ shy “ rooters are being inserted, even the amateur gardener might be well advised to use Hormone A.
There is no essential difference in method between aand a stem cutting.
Both need warmth, moisture, air and a clean, gritty rooting medium. To makea suitable leaf is scored across in several places on the underside, the cuts being made part way through a vein. The leaf is then laid flat on some sand or very sandy soil pegs are generally needed to ensure contact between the cut portions and the compost. As soon as roots form, the portions are severed and potted up separately. Similar conditions are needed for leaf as for stem cuttings. rex and gloxinias can be propagated in this way.
Any plant that makes suitable fleshy roots, such as the roots of the oriental poppy, can usually be successfully propagated by root cuttings. These are almost the same as root division, but no obviously growing stem or dormant “ eye “ is required on each portion. All that is done is to cut pieces of the thick fleshy root about the length and thickness of a man’s little finger, making a clean cut across both top and bottom. These pieces are planted in open gritty soil, the top being covered with perhaps 1 to 2 in. of the soil. Anchusa italica is a border plant that responds particularly to this form of increase, and as young plants are the showiest, it pays to treat a number of the roots in this way annually.
Offsets are another form of root division. Bulbs of all kinds when they reach their maximum size begin to split up, or send out small side bulbs or offsets. These can be taken off at any time during the dormant season, and if planted in congenial soil, they will eventually grow to full sized, flowering bulbs. The advantage of this method of bulb increase over the raising ofis, of course, that the young plants bear an exact resemblance to their parents.
It is worth noting that a bulb which is growing offsets in this way must have them removed, or serious overcrowding will soon result.