Gardening Techniques: Propagation

Nothing is more pleasant than to spend cold winter nights looking at seed catalogues and sending off a list of plants to your favourite nursery. Visions of bright colours fill the ‘inward eye’, and it is true that while a colourful garden and a well-filled vegetable plot can be had by buying in bedding plants and seedlings from the nurseryman, the cheapest and most interesting way of doing this is to start with seed. It is among the annual flowers that you will be looking for next season’s brilliant display, though you will probably order some biennials and perennials for planting later in the spring or summer to provide colour in the succeeding season or permanent background flowers.

But seeds are of little use without beds prepared for them – you should have the soil well broken up by the spring and rich with the previous autumn’s manuring. It is not too late to dig in the spring; it just means you will have to tamp the soil down with your heel instead of the slow action of the winter weather doing it for you. Light soils are warmer, so on sandy beds you will be able to sow quite early. They dry out easily too and are easier to work, but if you have quick-drying soil it might bean idea to put a little moist peat in the seed drills. Seeds need moisture, air and warmth to germinate, and it is necessary to break the soil down to a fine tilth using a rake, which will help to get rid of large stones and weeds as well.

Clay tends to be colder than sandy soil and it is difficult to work when cold and wet. You must wait for the right moment to get it into condition and weigh carefully when to sow. If you sow too early you may lose the seed through the cold. Some gardeners cloche the beds they are sowing about two weeks beforehand to provide just enough extra warmth for the seeds to germinate. Sowing times are generally later in the north and on higher ground.

Seed

In general there are two ways of sowing seed out of doors — broadcast or in drills. When sowing broadcast, seed should be mixed with some fine sand and allowed to dribble out slowly through the fingers held fairly close to the ground. Sowing in rows or drills may be done in the same way using finger and thumb only and making sure you keep to the line of the drill which may be scratched in the soil with a dibber or broom handle, following the line indicated by using a garden line. Pelletted seeds are pleasant to sow because they are large enough to be placed one by one and each is covered by a capsule of food which gives the seed a good start. Mark sowings with labels.

Cover the seed with fine soil to about twice its own thickness. It is best to have some fine soil ready rather than rake over the soil around the seeds as the rake may collect all the seeds into one spot. When planting in rows: if you mix some fine soil with peat to cover the seeds, the rows appear as a dark line and warn others where you have been sowing. Larger seeds like peas and beans should be sown more deeply, say to 2 inches. If your garden is subject to the depredations of birds or mice you may soak the seed in a mild solution of Jeyes fluid or some other repellent substance.

In general sow as thinly as possible, water before sowing, and mark the seed labels with a pencil that will not weather off.

Starting seeds under heat indoors has many-advantages. Not only is the range of plants you can cultivate greatly increased, but you can have colourful garden flowers growing earlier because by the time the soil has warmed up enough for sowing outdoors the indoor propagated ones will be ready for hardening off and planting out. You do not necessarily need a greenhouse to do this. A heated propagating unit on a table by the window getting most light will do.

Seeds may be raised indoors in boxes such as those used for market plants, or in plastic trays or earthenware pans. Once heat is involved and the gardener goes indoors with his gardening, hygiene becomes important, and all ‘utensils’ must be cleaned with warm water and a weak disinfectant. The better the conditions the more precautions must be taken.

Pots and receptacles with large drainage holes must be lined with crocks at the bottom covered with a layer of coarse peat or sterilised fibrous loam. The soil, or compost, is then used to fill the container and firmed down lightly to within half an inch of the rim. If you use an unsterilised compost from the garden you risk soil-borne seeds, diseases and pests destroying your efforts. It is far better to buy a reliable proprietary seed compost, such as the John limes Seed Compost.

The compost should then be thoroughly soaked by standing it in a bowl of water. When the water has permeated to the surface, remove and drain. Then sow the seeds and cover with a sheet of glass and brown paper tucked in under the edge. Turn and wipe the glass regularly. Some seeds have been found to germinate well by tying a plastic bag round the whole box, and it is also possible to hold a plastic bag round a pot rim with an elastic band keeping the seed away from the light till it germinates. Once the first leaves appear, remove the brown paper, prop up the glass, or remove or loosen the plastic bag so that light and air can reach the seedling. If seedlings are left in the dark they may die.

While the plants still have their seed leaves they can be pricked off into other boxes of seed compost. Be careful when pricking off always to hold the plant by the leaf and not the stem which may look more robust than the leaf but is most delicate. Plant labels of metal, wood or plastic are useful for lifting seedlings. Every seed tray or pot should be clearly labelled or you will lose track of what is what.

Once the true leaves have formed it is time to move the plants into a richer compost such as the John Innes Potting No. 1 variety, carefully firming round the seedling each time it is moved. You will find every spare pan and every inch of space must be pressed into service so try to prepare in advance. Water the seedling with a fine rose or gentle spray and make sure the compost is always moist and that the temperature and ventilation are correct for the plant. When moved they should be given more damp, extra warmth and less light for three or four days. Avoid draughts and repot seedlings that were started in late winter or possibly earlier.

Before planting out, seedlings must be hardened off either by increasing ventilation in the greenhouse or by transferring them to a frame which can be propped open. At all times care must be taken to see that they are protected from excesses of climate. These may include too much heat through strong spring sunshine, as well as frost and cold at night when frames may have to be closed and covered with sacks. Strong wind and heavy rain may also result in fatal damage to the young plants.

By the end of May or the beginning of June most plants should be in their final positions in the garden.

It is possible to sow early vegetable crops in a cold frame, and in open ground further sowings may be made for later flowering or for intercropping in vegetable beds.

Soft Wood Cuttings

These are stem cuttings of various kinds, including those taken from herbaceous plants in late winter, spring or early summer. Many shrubs can also be propagated from half-ripe cuttings taken around about July.

Usually a longer piece of stem is taken than necessary and trimmed with a sharp blade just below a joint (node) or leaf bud. Soft growth from a black currant or tender growing heather stems might be given as typical examples. The reason they are trimmed just below a node or bud is because this is a vital point from which new roots will spring. Dip the cutting in a weak solution of fungicide and then dip the tip in a suitable hormone rooting powder. Use this sparingly: the right amount will stimulate root growth; too much will inhibit it. Shake the excess powder back into the tin and set the cutting in a prepared hole in moist John Innes Rooting Compost in a 6-inch pot prepared in the usual way with crocks and good fibrous drainage material at the bottom.

The cutting should be about six inches long and should have the lower leaves removed, leaving about four pairs at the top. The hole into which it is inserted should be about a third of its length and the soil should be carefully firmed round. Water and insert thin stakes round the pot protruding about nine inches. Cover the whole with a plastic-bag and secure the bag with an elastic band round the bag, pressing it against the stakes not the pot. This is so that water forming on the inside of the bag will run back into the compost. When new leaves appear you can be certain that the cutting has rooted. Remove the bag and give the rooted cutting a feed with weak liquid manure. Keep the plant in the pot until it has made reasonable roots. Then repot it into a larger pot or transfer it to open ground in the growing season. Using propagating boxes, cuttings may be rooted on a large scale and split up into pots on rooting.

Hard Wood Cuttings

These are also stem cuttings usually taken in late September or early winter. Unlike soft wood cuttings, which are generally rooted in warmth. Hard wood cuttings may be propagated in a cold frame or in the open garden. The cuttings are cut from the parent plant just below a lateral bud or with a heel of the old wood attached. A heel is a strip of the bark and old wood from the main stem to which the cutting was attached. Hard wood cuttings, as the name implies, are taken from woody plants. The length of hard wood cuttings should vary according to the size of leaves and twigs: short twigs and leaves, short cuttings, is the rule. Generally the size of the cutting varies between 6 and 12 inches.

Some plants, e.g. clematis and verbena, are best increased by ‘internodal’ cuttings, that is, a cutting taken about halfway between joints. As with other types of cutting all but the top four or five pairs of leaves are removed, a special hard wood-rooting hormone compound is used, and the cuttings set in pots or boxes in four or five inches of rooting compost. In open ground a slit is made in the ground by rocking a spade too and fro. And the bottom lined with sand. Masses of cuttings may-then be inserted about three or four inches apart and about one third of their length deep, and firmed. Frost sometimes causes cuttings to be lifted and they must be firmly pressed back into the ground.

Division

This is the easiest of all modes of plant propagation. All that need be done is lift the plant to be divided out of the ground and divide it into a number of small pieces. With herbaceous plants, each root section must have at least one good bud on it. Much is made of the use of two forks back to back for dividing plants. In practice, an axe or knife or bare hands perform the task more easily, except in the case of delicate fleshy roots, such as those of peonies, when wounds should be dipped in a mild fungicide to avoid infection. Single-rooted plants are obviously not suited for division.

Layering

This is one of the most natural forms of propagation, as some plants do it for themselves without any prompting from man.

Strawberries layer themselves naturally and the gardener helps this process by pegging down the strawberry runners in pots of peaty compost sunk in the soil round the plant. Hairpins are often used to peg them down. When the layers have rooted well the connections are cut and the new plants can be planted anywhere.

Many drooping plants like rhododendrons may be layered by making a small notch or shallow cut with a knife on the underside if a branch near the ground, then pegging it down and burying it under three or four inches of sharp sand and good soil. Remove the leaves of the underground section and use a secure peg such as a foot-long metal tent peg with a hook wide enough to hold the branch.

The soil around the layer must be kept moist. This is often done by placing a slab of stone over the layering point. Plants that may be so treated include carnations and pinks, lilac, heathers, winter and summer jasmine, chaenomeles (japonica), cotoneasters, wisterias, chimonathus, and so on. Autumn and throughout the dormant period is the time usually chosen for layering. Carnations and pinks are done after flowering.

Leaf Cuttings

These are very useful for propagating house plants. Choose healthy leaves and if you have a mist propagation unit you will be able to carry out this operation far more successfully, because moisture and heat are essential. Covering with a plastic bag as described under soft cuttings and keeping the plants in a warm temperature on a shaded window sill is quite satsfactory. Begonia rex will root if pieces of leaf are laid on sand after making light cuts across veins on the undersides. It is better to peg down the leaf with hairpins on a sandy compost in the case of plants like streptocarpus. Christmas cactus Zygocactus and similar plants may be propagated by inserting the leaves which are cut in the side of a pot filled with sandy compost. African violets Saintpaulia and plants like peperomias may be started by detaching a complete leaf and stalk and inserting the stalk in a hole made with a pencil in a compost of half-and-half peat and sand, or peat and Vermiculite. Gloxinias and ivies are also easily started in this way.

Root Cuttings

These are made by taking small sections of roots, say about 2 inches, and inserting them in deep sand compost so that the top of the cutting is just below the surface. Root cuttings are generally started in the autumn and kept in a frame or unheated greenhouse over winter. In spring top growth should have started and they can be potted off.

Pipings

Members of the pink family, such as carnations, may be increased by gently pulling out the tips of leading shoots at the first leaf node of the stem and inserting them in sandy compost.

Budding

This is a method of propagating chosen varieties of woody plants, such as roses, by attaching a bud on to a vigorous-rooting stock of the same family. Most of the roses grown in gardens are cultivated varieties growing on vigorous stocks like Rosa canina, the Dog Rose.

Using a razor-sharp knife (as in all propagating by cutting) cut a shallow slice of the selected bud and bark, from a fresh vigorous shoot which has been previously cut off the variety to be propagated. Remove the wood from beneath the bud, but make sure the base of the bud is not disturbed as this would ruin the whole operation. On the chosen stock make a T-shaped cut (in the instance of roses this should be at or just above soil level) cutting down to, but not into the wood under the softer bark. Open the T-cut slightly and slide the piece of bud and bark down to the base of the ‘T’. Tie up with raffia to make sure that the growing surfaces of both plants are firmly touching. Budding is usually done in summer, and a shoot should form on the stock by the following spring when other growth may be cut out altogether in favour of the new shoot.

Grafting

This is a more advanced technique than most of those so far discussed, and is sometimes done to add other varieties to established fruit trees in the interests of pollination, or renewing life in aged trees. It can be done by experts on soft-tissued plants with the aid of moisture and warmth. Grafting is usually done in spring when the rising sap makes success more likely. The pieces to be grafted on to the stocks are ‘heeled in’ a V-shaped trench, firmed in the previous autumn. The trench must be in a shady position to ensure the pieces (scions) are more dormant than the stock which is to receive the scion.

Whip and Tongue

This is best done when the stems of stock and scion are both about 1/2-inch in diameter. The stock is cut off about 6 inches from the ground with a sloping cut and slit vertically. A scion with four buds is cut below a bud to match the cut made on the stock with a slit tongue to fit the slit in the stock. The join is made with as much of the growing layers under the bark of the two plants meeting. The joint is tied firmly with raffia and covered with grafting wax.

Crown Grafting

This type of grafting is eminently suitable for renewing old trees. The main stems of the tree are cut back to about 2 feet from the trunk in January, and in April a further two inches are cut off. Slits are made in the bark of the branches, the slits being about 3 inches long. Thin tapering wedges are cut in the young scions which are to be grafted on, and these are fitted into the slits so that the growing layers under the bark meet. Raffia and wax are used to seal the union. There are a number of other forms of grafting adapted to various types of situation, such as stub grafting, used for renovating old stocks but not cutting the tree back as far as in crown grafting, and bridge grafting, which is used for repairing damage to bark.

04. September 2011 by admin
Categories: Gardening Techniques, Propagation | Tags: , | Comments Off on Gardening Techniques: Propagation

Facebook

Get the Facebook Likebox Slider Pro for WordPress