Stooling

Stooling is an entirely artificial system of propagating plants by layering, because a plant is grown just to develop new plants, which it will do year after year.

It is a technique that is principally used to produce specialized rootstocks that control the vigour and size of a tree, especially fruit trees. However it can be employed on any plant that will respond to severe annual pruning.

Plant a rooted layer, cutting or seedling in well-cultivated ground and label it. Establish for one growing season. Never use a plant that has been grafted as it will reproduce the rootstock and not the grafted variety. All clonal fruit-tree rootstocks should be designated emla, which indicates they are free from virus disease. During the early part of the dormant season, cut back the rootstock, leaving about 1-2 in of the stem above ground level.

In the following spring, earth up any shoots as soon as they are about 6 in long, so that the whole plant is covered. Work the soil down between the shoots so that each shoot is completely surrounded by soil. Do not delay earthing up as one of the most critical factors in stooling is excluding light from the plant at an early stage.

As the shoots grow, continue to earth them up until each shoot is buried to about 9 in.

No further action will now be necessary, unless the summer is particularly dry, when the soil should be watered to encourage the roots to develop. Just keep the soil around the stems warm and moist. Too much water will depress temperatures.

In early winter, after the leaves have fallen and the shoots are fully dormant, gently fork away the soil back down to the original level, so exposing the stool and its shoots. The base of each shoot should have produced roots.

Remove these rooted layers from the parent stool. With a pair of secateurs cut them flush with the stool, so that no stub remains. Replant them immediately and label them clearly.

After removing and replanting the rooted layers, cultivate the soil around the stool and clean off any residual earth on the stool itself so that it is fully exposed to the elements. This is necessary to ensure that the buds receive adequate winter chilling and will therefore break evenly the following spring, when the whole process is repeated, except that a general fertilizer is added at about 4 oz to the square yard. Successful production will depend on looking after the stool.

4 Continue to earth up until each shoot is buried to about 9 in in soil.

5 Fork away all the soil in early winter once the leaves have fallen.

6 Cut off any rooted layers flush with the stool, using a pair of secateurs.

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1 Plant a labelled rooted layer in well-cultivated soil. Allow it to establish for one growing season.

2 Cut off all but the bottom 1-2 in of the stem during the early part of the dormant season.

3 Cover the plant with earth as soon as the shoots are 6 in long. Firm the soil between each shoot.

1 Plant a labelled rooted layer in well-cultivated soil. Allow it to establish for one growing season.

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7 Replant each rooted layer immediately into the open ground and label it.

8 Cultivate the soil around the stool, which should then be cleaned well.

9 Add a general fertilizer, at about 4 oz to the square yard the following spring.

French layering

[ rench layering is an extension of stooling and, as such, it also requires a specially grown plant from which new plants can develop. Like stooling, it produces an annual crop of rooted layers, but initially it takes longer for the sequence to become established.

Cultivate some ground by digging deeply and adding some organic matter, peat and grit. Plant a rooted layer and label it. Allow it to establish for a growing season. During the early part of the dormant season, cut it back to 1-2 in above ground level.

Leave the plant to grow undisturbed during the following growing season.

After the leaves have dropped, reduce any shoots to a manageable number—say, at the most, eight strong shoots. Cut back their tips so that each stem is the same length; then peg them down horizontally over the ground. By positioning the stems horizontally early in the winter, the buds will break evenly along the entire length of the shoots in spring.

In spring, unpeg the stems when their shoots are about 2-3 in long. Cultivate the

1 Plant a rooted layer and label it. Allow it to establish for a growing season.

2 Cut off all but 1-2 in of the stem in the early part of the dormant season.

1 Plant a rooted layer and label it. Allow it to establish for a growing season.

2 Cut off all but 1-2 in of the stem in the early part of the dormant season.

3 Reduce the shoots to eight after leaf-fall the following year.

7 Drop each stem into a trench 2 in deep. Cover, leaving shoot tips exposed.

8 Earth up the new shoots as they grow until the mound is about 6 in high.

9 Fork away the soil mounds at the end of the growing season.

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[Kluis uillnus) v«r|p(lr> DokwoikI, iol<Hirr>d hark M«|ilf—tomr s|)i"cifi ground. Space out the stems evenly in a star arrangement around the stool, and make a trench 2 in deep under each stem. Drop each stem into its trench and cover it until only the tips of the new shoots are exposed.

Earth up the new shoots as they grow, always keeping the tips exposed, until the mound is about 6 in aboveground level. Water the layers only if the weather is particularly dry. Do not overwater.

The central stool meanwhile will be producing a fresh crop of shoots, and it is these that will provide the next year's stems for pegging down.

Gently fork away the soil mounds, after leaf-fall. Cut away the rooted stems flush with the stool, avoiding the current year's growth. Divide each stem into individual plants with their own root systems. Plant these out immediately; label and water in.

Reduce the current year's growth on the stool to, say, eight strong shoots, and prune to an equal length. Peg these down on the ground so that the sequence can continue.

4 Cut back the growing tips so each shoot is the same length.

5 Peg down these stems horizontally over the ground.

6 Unpeg the stems when their shoots are 2-3 in long. Cultivate the ground.

10 Cut away the stems flush with the stool. Ignore any new growth on the stool.

11 Divide each stem into individual plants with their own root systems.

12 Replant immediately in the open ground. Label and water in well.

Dropping

This technique is used to propagate numerous heaths and heathers, dwarf rhododendrons and other related plants, and any shrub of suitable habit that is not readily propagated by other methods.

A plant that is already mature, and possibly even straggly, is dug up with a reasonably sized root ball. It is then completely buried so only the tips of the branches show. These branches will root, and they are then lifted, separated, and planted out to establish as new plants.

Dropping is not necessarily the most desirable method of propagating plants as often the resulting layers are less shapely than those produced by cuttings, but it is easy and simple to follow.

Prepare a plant in the dormant season by pruning it rigorously to encourage new, strong-growing stems with a high capacity to produce roots. Older, non-pruned stems will respond less satisfactorily to propagation but will nevertheless usually regenerate.

Dropping is normally done in spring before growth begins, but once the ground is no longer frozen, so the soil can be broken down to a tilth.

Cultivate some soil and incorporate peat and grit if the soil is heavy and likely to become waterlogged. This will lighten it and improve aeration.

Excavate a hole large enough for the whole plant to be "dropped" into it, leaving only the tips of the stems visible. Dig the base of the hole well to allow efficient drainage, otherwise waterlogging will discourage successful rooting.

Lift the plant with as complete a root ball as possible. Place it in the hole and arrange its branches in any of three different patterns within the hole; the choice will depend upon the habit of the plant under consideration.

Whichever pattern of dropping is used, ensure that only 1 in or so of the stem tips are exposed: greater exposure of stem will cause the new growth to be leggy. Cover the plant with soil, firm in and label.

Water during the growing season if the soil dries.

Lift the whole plant in autumn. The branches will have rooted, usually fairly close to the soil surface. Cut away each division and plant it out or pot it up. Label clearly. Discard the old stool.

1 Prune a plant in the dormant season to induce stems with a high capacity to produce roots.

2 Cultivate some soil the following spring. Add peat and grit if necessary. Dig a very large hole.

3 Lift the plant with as complete a root ball as possible. Place it in the hole.

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Compress the branches into a single row towards the middle of the plant if the branching is sparse. This pattern saves space and makes weeding easy. It should not be done if the plant produces a thick mass of stems as rooting will not be satisfactory if there is insufficient room for the roots to develop.

In those plants with brittle branches, work the soil down among them so that each stem is surrounded. This pattern is more difficult to keep weed-free.

The traditional pattern is to excavate a bowl-shaped hole and to push out all the branches to the perimeter, and fill in the middle of the hole with soil. This pattern is easy to weed but is wasteful of space.

4 Leave only 1 in of the stem tips exposed when covering the plant with soil. Firm it in and label.

5 Water during the growing season if the soil dries.

6 Lift the plant in autumn. Cut away each rooted stem and plant it out or pot it up. Label clearly.

Stem cuttings

Growing plants from stem cuttings is by far the most popular method of vegetative propagation. However, only in the last 150 years, since the availability of cheap materials

I and the development of greenhouses, cold frames, etc., has it played a significant part in vegetative propagation.

The main difficulty about taking stem

¡cuttings is that a stem, separated from its parent plant, has to survive while it initiates and develops roots and establishes itself as a new plant. This distinguishes the technique | from layering (see page 54), in which the stem is not separated from the parent plant until after a new root system is produced.

Because a stem cutting has no support system from the parent plant, it is necessary I for the gardener to supply this himself. He I should ensure that the propagating environment will not only enhance root development | but also maintain the cutting until it is [ self-supporting.

1 Selecting a suitable stem

  • The ability of a stem to produce roots will be f dependent on the age of the parent plant and
  • its particular variety, and on the stem to be propagated (see page 53). The gardener should try to propagate from a plant that ■ has recently matured and is a relatively new ^ variety rather than an old plant or old variety . of plant.
  • The parent plant should be pruned rigor-| ously to encourage it to produce fast-growing vegetative shoots from which stem cuttings • will be made, as these shoots are most likely

Ito produce roots. The harder the plant is pruned, the faster will be the new growth. The whole success of propagation by stem I cuttings depends on the ability of the stem ^ to produce roots—and if this is absent or at I a very low level, then the stem should be discarded.

L A stem's ability to produce roots may have seasonal fluctuations, but this depends on the [ condition of the stem, that is whether it is t soft wood, hard wood, etc. A softwood cutting is taken soon after the buds have started growing in spring, and it has a greater ability to produce roots than a hardwood cutting, which is taken at the end of the growing season. However, because the soft wood stem is still immature, it is more susceptible to water loss, rot and disease, and it therefore requires a highly controlled environment in which to develop.

A stem cutting's food reserve is used not only to initiate roots but also to maintain the cutting until it is fully .established as a new plant. The size of the reserve depends on the condition of the stem: a cutting from a mature (hardwood) stem will be able to survive much longer than an immature (softwood) cutting. A cutting should therefore be encouraged to develop roots as quickly as possible to avoid exhausting its food reserve. It should also be exposed as little as possible to variable weather conditions to prevent it drying out—leafy cuttings being particularly prone to water loss.

A cutting should be taken from a fast-growing stem from the current year's growth at the correct season for the condition of the stem (for example, green wood in early summer, hard wood during the dormant season). It should then produce roots quite readily, without the artificial aid of rooting hormones; if it is dipped in hormone, the treatment is likely to have little or no effect. However for plants that are difficult to root, dip stem cuttings into a rooting hormone, or wound them, to stimulate the roots.

Environmental control

The rate at which a stem cutting develops its roots is dependent on the temperature around it. The processes controlling root initiation are essentially chemical; the higher .the temperature the faster the chemical reaction and thus'root production. However, if a whole cutting is kept warm, its tip will grow and food will be diverted from the important function of forming roots. Its food reserves may then be used up before the cutting has become self-supporting. Therefore, a cutting requires two temperatures: a cool, aerial environment to keep tip growth to a minimum, and warmth below to encourage root production.

The exact temperatures vary with the condition of the stem and how susceptible it is to water loss. Softwood cuttings require bottom heat of about 21°C/70°F and as cool an aerial temperature as practical—a mist unit is ideal. Hardwood cuttings, on the other hand, are propagated outdoors where the soil is quite warm enough and the air, even when frosty, is not too cool. Greenwood, semi-ripe and evergreen cuttings need a warm, humid environment. This can be supplied by placing a small pot filled with water inside a pot that has the cuttings and compost in it and putting them under a polythene tent, or by placing the pot that has the cuttings and compost in it inside a larger pot filled with moist peat and putting them under a polythene tent. However, the main disadvantage of these two environments is that it is easy for the gardener to overwater and so kill the cuttings through rotting and fungal diseases unless extreme care is taken. Cold frames, closed cases and polythene tunnels are' therefore preferable.

Different stem conditions

A stem cutting can be divided into five wood conditions for the purposes of propagation.

Softwood cuttings have leaves and are made from the first flush of growth in spring. Their stems are normally very soft because they have grown extremely rapidly; and they require sophisticated environmental controls to minimize water loss and so ensure their survival until they become established.

Greenwood cuttings are made from the tips of the leafy stems during early to midsummer. Their stems are soft, although harder than softwood cuttings, and they should be propagated in a controlled environment, such as a closed case.

Semi-ripe cuttings are made in late summer from stem growth that has slowed and hardened but is still actively growing. Although these leafy stems are subject to water loss, they can survive under less rigorous environmental controls than softer wood cuttings.

Ripewood cuttings are stems taken from evergreen plants during winter. They have almost hardwood stems but, because they are leafy, they are not entirely dormant and will require some degree of environmental control.

Hardwood cuttings are made from leafless dormant stems of deciduous plants. They require minimal environmental control for survival.

WHERE TO CUT A STEM

A nodal cutting has its basal cut just in) below a bud, or node. It is the traditional place to cut soft, immature stems as a stem just below a node is harder and more resistant to fungal rots than a stem cut further away from the nodes. This latter cut is known as an internodal cut, and it is used mainly for more mature, woodier stems.

Other methods of taking a cutting are leaf-bud, heel or mallet cuttings (see pages 62-3) or vine-eye cuttings (see page 73). The index at the back of the book will refer to these methods when appropriate.

Nodal cutting Internodal cutting

Nodal cutting Internodal cutting

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