Vegetative Propagation: Types of Cutting and Equipment Used
For most plants this is the quickest, easiest and cheapest method of propagation, and also provides a sure way of perpetuating a kind or variety in the exact likeness of the parent plant. For this reason the method is in common use, especially for the raising of plants with double flowers and those that have coloured or variegated foliage. Generally the term ‘’ refers to any portions removed from the stem, leaves or roots of the parent plant. If such cuttings are properly prepared and inserted they will produce new plants with the same characteristics as the parent plant.
The first priority is a good sharp knife that should not be too large or too small for the hand, and have a thin, straight-edged blade. There are various forms of knife on the market and the long-handled budding knife is, in spite of its name, very useful and the most suitable for making cuttings. A safety razor blade mounted in a suitable handle is useful for making, like those of , dahlia and similar non-woody plants.
A good pair of secateurs, preferably of the knife-blade type, will be needed, especially where cuttings are to be taken of woody plants, that is, shrubs and trees. Like the knife, the blade of the secateurs must always be sharp to ensure a clean cut.
For the insertion of the cuttings several dibbers of varying size are needed. They should be made of hard wood and not be too sharply pointed.
This is usually a small wooden frame in a greenhouse with a glass light to close down over it. The light is attached to the back of the frame with hinges so that it does not move out of position when lifted at the front. The frame can vary from an ordinary box covered by a pane or panes of glass to an elaborate span or lean-to type of frame specially constructed by a builder. Whatever its form and size, the purpose of a propagating frame is to provide a close atmosphere that can be controlled to the correct temperature and humidity. Thus the amount of air round-the cuttings is reduced in order to keep them in a turgid condition while they root. The other essentials for rooting are sufficient moisture and heat. Place over the base of the frame an ash or shingle covering on which the pots of cuttings can be stood, and keep it damp by spraying. If desired, the frame can be partly filled with the rooting media (sharp, clean sand or a mixture of sand and peat) and the cuttings inserted directly into it.
Sharp silver sand is the best rooting medium for most cuttings, as long as they are removed from it as soon as they are well rooted, because sand contains little or no nourishment.
A mixture of equal parts sand and peatmoss gives good results, particularly if the cuttings have to be left in the frame or receptacles for a time after the roots have formed. Other rooting media available include: vermiculite, various kinds of sand and a powdered volcanic rock known as ‘Rootine’. The John Innes pottingis also available ready mixed from nurserymen and nurserymen.
Scientific research has produced chemical growth substances known as hormones, and these in liquid or powder form can be used as an aid to the quicker and better rooting of cuttings. There are different types for the treatment of soft wood cuttings, half-ripe or ripe wood cuttings. The hormone preparations, under various proprietary trade names, can be obtained from shops selling horticultural goods, and should be used strictly according to the makers’ directions.
A conveniently sized watering-can with a set of fine spray roses (flat and round) is essential for watering. A syringe of the ‘Abol’ type with a bent nozzle and several detachable jets of varying sizes should also be available, as a fine spray of some kind is necessary for damping the cuttings and keeping the frame moist. Receptacles (pots, pans and boxes) of varying sizes are needed for different batches of cuttings. The advantage of receptacles is that once the cuttings are inserted in them they can be rearranged in the frame. Clean the pots and put in a layer of crocks in the same way as for. Bell-glasses or solid cloches used to be popular to place over cuttings dibbled into pots or a bed, but are not now easy to obtain. Polythene bags can be used to cover individual pots or pans of cuttings, but a wire support or small sticks should be provided to keep the polythene clear of the foliage, and also rubber bands to anchor the polythene to the pots.
TYPES OF CUTTING
These are pieces of growth taken from the aerial parts of the parent plant, and can be either side shoots or the tips of main shoots. They can be of soft wood, half-ripened wood or ripe wood. Soft wood cuttings are made from the young tender growth of the current season; half-ripened cuttings are made from semi-ripened wood that has been growing for some time and become slightly woody or firm (usually about midsummer); ripe wood or hard wood cuttings are made from mature wood at the end of the growing season and are chiefly used for the propagation of trees and shrubs.
All stem cuttings are prepared by removing the lower leaves from the piece that has been cut from the parent plant, and then cutting straight across the stem just below a joint or node. The cuttings should be about 3 in. long. In the case of ripe wood cuttings they can be made with a ‘heel’ of the older wood attached at the base and be up to 10 or 12 in. long.
These are made from half-ripened wood and consist of one leaf with a dormant bud at its base and also a portion of the stem. They are inserted in the same way as stem cuttings, but with the leaf and bud just above the surface of the rooting medium. This type of cutting is used particularly for the propagation ofand some other evergreens,’ and has the advantage of providing a greater number of young plants from one piece of growth than are provided by a stem cutting.
Bud or eye cuttings:
These are similar to leaf-bud cuttings but with no leaf attached, and are made from dormant ripened wood in autumn or winter. Ornamental and fruiting vines are propagated from this type of cutting. Make each cutting of woody stem with a single dormant bud or eye about 1-1/2in. Long. Take off a strip of bark and wood on the side opposite to the bud, then insert the cutting on its own in a small pot of potting compost with the bud just atlevel. Label and keep it moist and close until a tiny shoot begins to sprout. Leaf cuttings: Quite a number of plants, particularly greenhouse plants, can be propagated from . , , saintpaulias, streptocarpus and echeverias are examples. Remove the leaves from the parent plant with the leaf-stem attached and, after cutting the end of the stem cleanly, insert it into the soil or sand so that the leaf blade lies flat along the surface. A young plantlet will rise from the base of the cut leaf stalk after little roots have formed. Lay the leaves of large-leaved of the B. rex type on boxes of sandy peat after the main veins on the back of the leaf have been severed with a sharp knife or razor blade. The young plantlets will develop where the veins were cut and root into the soil. By this method a number of young plants can be obtained from a single leaf.
There are a number of plants, both shrubby and herbaceous, that can be propagated by: for example, the perennial phlox, verbascum, hollyhock, romneya, Anemone japonica, eryngium, gaillardia, anchusa and oriental poppy. The method is simple. Lift a complete plant during the dormant season and cut sections of the larger and more fleshy roots into pieces, called thongs, about 2 to 3 in. long. Cut the end of the root nearest the crown of the plant (the top) straight across, and cut the other end on the slant. The different types of cut makes it easy to distinguish the top end of the cuttings from the lower.
Insert the root cuttings into pots or boxes of potting compost with the straight cut just at soil level. Then plunge the receptacles into beds of ashes or peat until the cuttings have rooted and growing points or crowns are formed at their top ends.
During early spring plant the cuttings out singly in nursery beds or a border to grow on and form flowering plants for the next year. If desired, large quantities of cuttings of the same kind can be tied in bundles and plunged in sand or soil to root.
It is unnecessary to distinguish the ends of the cuttings of some plants, particularly the perennial phlox. The selected roots can be cut into 1-in. lengths, laid horizontally on sandy soil and lightly covered with sand. If they are placed in a frame or greenhouse, a young plantlet will develop from each piece of root.
Carnations and pinks are propagated by pieces of the young tip growth called pipings. This type of cutting needs no trimming. Hold the growth or shoot in one hand and then pull out the tip of the shoot with the other hand. Insert the piping in sandy soil in a closed frame or at the edge of a pot of sandy compost and cover it with a polythene bag.
INSERTING THE CUTTINGS
It is important to realize that, no matter how well the work of preparing the cuttings is done, they will not root properly unless they are inserted correctly.
The natural healing of a wound in plants is much the same as in animals, because new tissue is formed to grow over and cover the damaged area. Thus, when a cutting is made or prepared by cutting it cleanly just below a joint or node, the cells that are damaged by the knife-cut die and, as a result, a corky layer of tissue, termed ‘callus’, is formed. Under favourable conditions — giving warmth and moisture — the callus forms a ring round the edge of the wound. From here, roots grow out, anchor themselves into the soil and produce root hairs which absorb moisture and food, thus providing the cutting with the means to continue a separate existence.
Sometimes, however, cuttings will make a lot of callus formation at the expense of roots — in fact they will appear to be growing yet will produce only a drumstick-like end to the part below soil level and no sign of a root. This may be caused by high soil temperature, or a coarse rooting medium which allows too much air to penetrate to the base of the cutting. The use of very coarse sand, such as Cornish sand, has been found to cause excessive callus formation. To overcome this difficulty, shave off the excessive callus with a razor-blade or small, sharp knife. This will often cause roots to form quickly after the cutting is reinserted.
The method of insertion is much the same for all kinds of stem cuttings. The prepared ends should be firmly embedded in the rooting medium, so that the cutting does not hang in the hole made by the dibber. If the soil is pressed round the cutting at the surface and left loose at the base, the cutting will fail to root because of the air space round the lower end. Insertion to a depth of 1 in. or 1-1/2 in. is usually ample for the average cutting, but the larger ones, particularly those made from hard wood and placed in outdoor beds, need a depth of 4 or 5 in., or about half the length of the cutting.
It is advisable to sprinkle a layer of dry sand over the surface of the compost when preparing the pots, because when the dibber is pushed into the soil it will take a quantity of the sand to the bottom of the hole, and on this the base of the cutting can rest. Use a dibber with a blunt or square end to make the hole. Push it in to the required depth and put the cutting in so that its end rests firmly on the base of the hole. Then fill in by pushing the soil in and gently ramming at the side of the cutting with the dibber. After inserting, always water in with a watering-can fitted with a fine rose, to settle the soil and make it firm round the cutting.
CUTTINGS IN OUTDOOR BEDS
Hard wood or ripened cuttings, of which those of rambler or climbing roses, hardy shrubs and bush fruits are typical, are prepared from ripened growth during late summer or early autumn. They should be about 10 to 12 in. long and have a heel of older wood at the base. Heel cuttings are essential for any plants that have pithy wood or stems.
Insertion of this type of cutting into prepared beds is not difficult, but the soil should be fine and firm. Cut out a small narrow trench with a spade and, if the soil is inclined to be heavy, sprinkle some sharp sand along the bottom of the trench. Then space the cuttings 3 or 4 in. apart against the vertical side of the trench with the heel ends firmly on the base, fill in the soil and make it firm by treading or ramming. At least half of each cutting should be in the soil; nurserymen often insert two-thirds.
Leave the cuttings in the bed for a year, by which time they will be well rooted. The bed requires little attention, and need be watered only if the weather is very dry. Growth starts in early spring, and this will generally indicate the success or failure of the cuttings. If they are successful leave the bed undisturbed for the summer, but keepin check. During the autumn transplant the young plants into well-prepared ground, for they must have ample growing space to develop their true habit of growth. Put them in rows 2-½ ft. apart and leave l-1/2 to 2 ft. between the plants, to allow easy access between them for hoeing and cultivating, and for staking and tying if necessary. According to type and variety and its mode of growth, the young plant can remain in the nursery bed for one or two years, but it is unwise to delay trans-planting into the permanent position for longer than is necessary.