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Techniques : Vegetative propagation

Division | Indoor cuttings | Outdoor cuttings | Layering

There are several ways of raising new plants that do not involve seed sowing. These include division, cuttings, layering and grafting, and they have the advantage of exactly reproducing the parent, since the new plant is raised vegetatively from a part of the parent.

Division

Many plants reproduce naturally by vegetative means, using runners, bulbils, offsets or just additional crowns. These can be raised as new plants as soon as they have produced a few roots of their own, and sometimes even before.

Day lily planted divided

Day lily planted divided

Simply separate them from the parent, cutting runners, breaking away bulbils and offsets, and dividing or cutting away groups of healthy crowns. Division is the main method of raising new plants of perennial flowers, many house plants and quite a few rockery plants.

Indoor cuttings

Semi-hardwood cuttings are rooted indoors – under protection of some sort. ‘Semi-hardwood’ describes the stage of growth of the shoot from which the cutting is made. In July, August and September, the young shoots have almost fully extended, and they begin to turn woody at the base as part of the ripening process before winter. These young shoots are full of growth and vigour, and root relatively easily.

Potting on rooted euonymus cuttings

Potting on rooted euonymus cuttings

Prepare cuttings between 5 and 15 centimetres long depending on the type of plant. Trim the base with a sharp blade, just below a leaf or pair of leaves. Remove the leaves from the bottom half of the cutting and dip it in rooting powder, such as Keriroot, Murphy Rooting Powder, Bio Roota, Strike or Seradix.

Insert the cuttings into trays or pots of 50:50 peat/sand mix, at about 5 by 5 centimetres apart. Use only clean horticultural sand. Firm the cuttings and water them lightly.
Tie a white polythene sheet or bag over the pot or tray, piercing a few small holes to let air in.

Place the tray in a shaded part of a greenhouse, or in a bright, but sunless, window in the house. Semi-hardwood cuttings can also be placed in a shaded garden frame in trays, or, if a lot of cuttings are to be rooted, inserted directly into the same peat/sand mixture in the frame itself.

The taking of semi-hardwood cuttings is a suitable way of propagating a wide range of shrubs. The same technique is used, without polythene, for alpines and some house plants such as campanula, fuchsia, geraniums, ivy, busy lizzie, and succulents.

When the cuttings begin to produce new leaves, remove the polythene, and water as necessary until roots appear at the drainage holes. This may only take six weeks with fast growers. At this stage, the cuttings should be potted singly, in 8 centimetre pots of good potting compost, and grown on – unless it is getting into late autumn.

In that case, leave the potting-up until March or April. The young plants can be potted into larger pots, or planted out into nursery beds, to put on some size before planting into their permanent positions.

Outdoor cuttings

Although not suitable for such a wide range of trees and shrubs as the semi-hardwood method, this technique is both simple and effective. In late autumn, at the end of the growing season, the young shoots will have become quite woody and hard – hence ‘hardwood’ cuttings.

Take 25 to 30 centimetre pieces of the young shoots. Leaves might or might not be present – some kinds are deciduous, other evergreen. Trim the shoot below a bud and take off any lower leaves. Insert the cuttings in 15 centimetre deep trenches, with some clean sand at the bottom, in a sheltered part of the garden.

Fill back the top-soil and firm well. Space the cuttings 15 to 30 centimetres apart. Trees and shrubs for which this technique is suitable include poplar, willow, blackcurrant, gooseberry, griselinia, escallonia, forsythia, roses, bay laurel, dogwood, tamarisk and flowering currant.

Leave the cuttings in position for a year keeping them free of weeds. The following autumn, plant them in nursery rows, or into their final position.

Layering

For shrubs that are difficult to root, such as rhododendron and clematis, or when only one or two new plants are required, layering is a useful technique. Select a branch that is young and bends to ground level fairly easily. Remove leaves if they are in the way.

Make a 5 centimetre sloping cut in the branch, cutting halfway through. Insert a match stick to keep the wound open, and dust with rooting powder. Make a shallow depression in the soil; fill it with good compost and a little sand mixed in; press the branch gently down onto this; and pin it in place with a strong piece of bent wire.

Heap on some more compost. Place a heavy stone, or sod, on top, to keep the whole arrangement steady. Layering is done in June or July and the new plant is cut away when it has clearly rooted, usually eighteen months later.

A form of layering called air layering can be used if branches do not reach soil level. Prepare the branch in the manner described and place a plastic bag with the bottom removed over the rooting point, tying it below. Fill the bag with moist compost and tie it again above the compost to hold it tight. The weight of the layering bag may need to be supported.

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