Expert Tips for Propagating Trees and Shrubs
Propagating Trees and Shrubs
If I were asked which branch of gardening gave me most satisfaction I might well say ‘everything to do with propagation’. There is nothing quite like the thrill of seeing difficult plants successfully raised from seed, a frame full of healthy softwood cuttings prepared by your own hands, or a graft which has ‘taken’ when the ‘marrying together’ proved rather a tricky job.
Various methods of increase can be adopted, such as cuttings, seed,, , grafting, budding and division and I will deal with each of these in turn.
This is undoubtedly the most widely used method of propagating trees and shrubs. There are two main types of cuttings which can be taken, each of which requires a different technique and rooting conditions.
First, there are half-ripe cuttings which are taken during the summer and, secondly, there are hard-wood cuttings which are taken during autumn.
HALF RIPE STEM CUTTINGS
Propagating trees or shrubs by the cuttings method is incredibly rewarding. Many of our popular garden shrubs can be propagated by half-ripe cuttings. These include abelia, buddleia, caryopteris, ceanothus, cotoneaster, deutzia, escallonia,, hebe, heathers, hydrangea, potentilla, rosemary, santolina, senecio, viburnum and .
Selecting Suitable Shoots
Half-ripe cuttings, which are taken during July, August or September, are obtained from the current year’s shoots. These shoots, as the name suggests, are only half-ripe, that is, the wood has not completely hardened. You should avoid any shoots which are still rather soft; you may, therefore, have to be patient for a week or two until they have hardened and ripened slightly.
Preparing the Stem Cuttings
I find it best to pull off the shoots with a heel of older wood attached, and the stem cuttings, when prepared, are 6 to 8 inches long. If the tip of a shoot is very soft then I cut it off. Some gardeners like to cut off the shoots just below a leaf joint, but the method used depends upon personal preference.
Heather cuttings, incidentally, are best taken with a heel and should be about 1 to 2 inches in length. The leaves on the lower half of all cuttings must be cut off with a sharp knife, close to the stem.
Suitable Rooting Mediums
I prefer a mixture of equal parts by bulk of loam, peat and sand, but a mixture of equal parts peat and sand is also suitable, particularly for cuttings of lime-hating plants.
Inserting the Stem Cuttings
The stem cuttings can be inserted in a cold frame, about 2 inches apart each way, with half their length below the. Before I insert them, however, I like to dip the base first in water and then in a hormone rooting powder to assist in rapid root development. I use a piece of wood, shaped rather like a pencil (known as a dibber), for making the planting holes.
I then firm the cuttings thoroughly with this, paying particular attention to their bases. The base of each cutting must be in close contact with the soil, otherwise roots will not form.
I water the cuttings thoroughly to settle them in and then close the frame. They like a moist, close atmosphere as this encourages them to root more quickly. The frame can be kept closed for three or four weeks, opening it only for a few minutes each morning to allow condensation to drain from the underside of the glass.
I also syringe the cuttings for the first week or two to keep the leaves moist and to prevent flagging. After about four weeks a little ventilation can be given, by which time many of the cuttings will be starting to form roots. Ventilation should then be gradually increased.
The rooted cuttings remain in the frame during the winter and should be given plenty of air when the weather is fine. They must be protected with a frame light, though, during periods of heavy rain, snow or severe frost.
Planting Young Specimens
The young plants may be planted out in a nursery bed during the following spring, in rows about 18 inches apart with 12 inches between the plants. Many of them will be of a suitable size by the following autumn for planting out in their permanent positions.
Alternative Methods of Rooting
Half-ripe cuttings may also be rooted under a cloche, each end of which is sealed with a pane of glass. Some gardeners also root them in pots – placing the cuttings round the edge of the pot and enclosing them in a polythene bag. A heated propagating case in the greenhouse will encourage such cuttings to root rapidly, especially if the case has heat from below.
I consider mist propagation to be the quickest way of increasing shrubs at the present time. Half-ripe cuttings will root in as little as three weeks. Many of the large leaved evergreen shrubs which are normally difficult to increase will root comparatively easily under mist. The cuttings are usually inserted direct into a bed of sand in the mist unit, which is heated by electric soil-warming cables. The leaves of the cuttings are kept constantly moist by spray units which are automatically controlled. This prevents the cuttings from flagging. When the cuttings have rooted they are potted individually and put back under the mist to be gradually weaned off for about a week or so.
Cuttings which have been rooted under mist, or in a heated propagator, must be hardened off, first in a cool greenhouse and then in a cold frame, before planting them in the open ground.
HARD WOOD STEM CUTTINGS
These are taken in the autumn when shrubs or trees are devoid of leaves. I usually take mine during November. Again, the current year’s wood is used for cuttings, but at this time of year it is really well-ripened and hard. There are many shrubs which can be increased from hard-wood cuttings, including Cormus alba, C. stolonifera, forsythia, garrya, laburnum, philadelphus, privet, ribes, sambucus, tamarix and willows (Salix).
Taking the Cuttings
I remove the shoots with a heel of older wood attached, trim this smooth and cut off the tip of the shoot just above a bud to give me a cutting 9 – 10 inches in length. Some gardeners prefer to cut the base of the shoot just below a leaf joint. These cuttings may be up to 1/4 inch thick, but avoid using any weak or spindly shoots.
Inserting the Stem Cuttings
Hardwood cuttings are rooted in the open ground, so try to select a sheltered situation for them. The easiest way to insert them is to make a trench (with one vertical side) sufficiently deep to allow the cuttings to be inserted to about two-thirds of their length. Unless the soil is very light and well drained it is best to place a layer of coarse sand along the bottom of the trench.
Before I insert the cuttings, I dip the base of each in a hormone rooting powder. They are then placed along the trench, against the vertical side and about 2 inches apart, with the base of each cutting in close contact with the sand. Then the soil is returned to the trench and the cuttings are firmed thoroughly.
If frost loosens the stem cuttings, they should be re-firmed as soon as possible, otherwise they may not form roots. Leave them in the bed until the following autumn when they can be lifted and planted out into a nursery bed, about 1 foot apart in rows 2 feet apart.
When propagating trees and shrubs, follow these expert tips and you will have untold successes.