2. Propagators and Propagation

Propagation by 'Cuttings'

To raise plants from 'cuttings', it is necessary to use a propa­gating case for most kinds. In this apparatus suitable conditions can be provided to ensure that the 'cuttings' remain in a fresh condition during the period of rooting.

The simplest form of propagator consists of a box about 12 inches deep. It should have a layer of pieces of broken flower-pot or some rough siftings from the compost, placed in the bottom, to the depth of 2-3 inches, to provide drainage. The drainage materials should then be covered with a thin layer of undecayed leaves to prevent the compost from being washed down into the drainage layer.

The best propagating compost consists of equal parts of granula­ted peat (put through a sieve, having a ^-inch mesh) and coarse silver sand. This compost should be moistened before it is placed in the propagator. It should then be pressed lightly into the propagator, leaving a space of about 4 inches above the compost. Finally, a pane of glass should be placed on top of the box to maintain a moist atmosphere.

Instead of a mixture of sand and peat, 'Vermiculite' may be used as a propagating material. 'Vermiculite' is pest free and stimulates root production. In a simply constructed apparatus of this kind it is possible to 'strike' 'cuttings' of a variety of plants. The propagator can be set on a tray to catch drainage water, if it is used in a room, or it can be placed on the staging in a greenhouse.

The Use of Bottom Heat

Root development can be speeded up by the use of an apparatus which provides warmth at the base of the propagating case. This warmth can be obtained by standing the box in a metal tray set on the hot-water pipes or a radiator. By this means the propagating compost can be maintained at an average temperature of 6o° F. Special equipment, heated by electricity, and thermostatically controlled, is obtainable. This is ideal because it provides a con­stant temperature and needs only the minimum of attention.

Preparation of the 'Cuttings'

When selecting shoots to be used as 'cuttings', choose those which are free from pests (or clean them) and are of healthy appearance and of vigorous growth. Cut them off just below a node or joint, and remove sufficient of the lower leaves to allow the 'cuttings' to be inserted in the compost (Fig. 2).

Fig. 2. Hydrangea cutting prepared Some leaves removed and the stem cut off just below a node or joint

The prepared 'cuttings' can be set directly into the bed of compost, in the propagating case, or they can be inserted around the edges of small pots. These pots of 'cuttings' should afterwards be plunged up to their rims in the bed of compost in the propa­gating case.

After-treatment of the Rooted 'Cuttings'

After the 'cuttings' have been inserted in the compost, it must be well watered. The lid of the propagator must then be closed down, to maintain a moist atmosphere, which is necessary to keep the 'cuttings' in a fresh condition. Once the 'cuttings' have been inserted they should not be allowed to wilt; but very little watering will be needed until roots have been formed, because moisture will not evaporate quickly from the closed case.

Each day the moisture which has condensed on the underside of the glass must be wiped off and the lid of the propagator closed immediately.

This procedure should continue until roots have formed at the bases of the 'cuttings'; then the case can be ventilated by propping up the lid about i inch for the first day or two. Gradually the ventilation is increased daily until the case is fully ventilated.

By that time the rooted shoots will be ready for setting in separate 3-inch pots: at this stage, the young plants should be set in John Innes Potting Compost No. 1, or a mixture of equal parts of loam and peat or leaf-mould may be used with a \ part of silver sand added. (Composts for special plants arc given in the alphabetical list in Chapter 6.)

These small pots do not require much drainage material and it is sufficient to put an inch layer of rough siftings of the compost in the bottoms, before potting is done.

This amount of drainage material is adequate for most plants for their first potting but for slow-growing plants it is best to drain the pots with crocks (pieces of broken flower-pot) to the depth of half an inch.

After potting, the plants should be well watered to settle the compost close to the roots. If space is available, set the potted plants in the propagator for a few days, by which time the roots will have penetrated the compost. The plants can then be taken from the case and exposed to the atmosphere of the dwelling-room or the greenhouse.

Potting of the Young Plants

Most plants raised from 'cuttings' and set in small pots must be later transferred to 5-inch pots.

This should be done as soon as the roots have reached the sides of the small pots and before a pot-bound condition results.

When repotting, great care must be taken to avoid disturbing the ball of soil around the roots. Remove the crocks with a pointed stick and set the plants straight into the larger pots. Then give them the same treatment as advised for repotting plants in a later section (Chapter 3).

A Portable Potting Tray

Those who do not possess a greenhouse or potting shed will find a portable potting tray of immense value. This tray should be made of ^-inch boards. It should be about 24 x 15 inches at the base with the sides and the back 9 inches high and the front 4 inches high.

Raising House Plants from Seeds

The principal house plants which are easy to raise by sowing seeds are Aloe (succulent plant), Asparagus species, Begonia semper-florensundB. rex, cacti (many kinds), Clivia, Cyclamen, Eucalyptus, Fuchsia (varieties), Grevillea robusta, Opuntia, Passijiora, Phoenix (palm), Primula malacoides and P. obconica, Ricinus, Rochea (suc­culent plant), Saintpaulia (hybrids) and Solatium capsicastrum.

The most suitable compost

All the above-mentioned seeds can be sown in the compost made up from the John Innes formula. This consists of:

It is best to sterilise the compost, and it should therefore be heated in a sterilising apparatus for 10 minutes at a temperature of 18o° F. After this partial sterilisation, the compost must be spread out on a bench to cool before use.

Sterilising Compost with Cheshunt Compound

Fig. 3. Watering a seed pan by partial immersion

A simple method of sterilising the compost is to water it with Cheshunt Compound steriliser. This chemical can be obtained from any seed store. It consists of a powder which, when dissolved in water, is sprinkled over the compost before or after the seeds have been sown. It is perfectly safe to use, and does not injure the smallest seedlings. Seed boxes and pots can be sterilised by this method and thereby made pest free. A satisfactory seed compost may be obtained by sterilising the loam only, and then adding the peat, sand and fertiliser.

Fig. 4. Sowing seeds mixed with sand to ensure even distribution

Preparing the Seed Compost

The soil ingredients are sifted through a sieve having a |-mch mesh and thoroughly mixed. The pots or seed pans are given plenty of drainage crocks which are covered with rough siftings from the compost, and the receptacles are then filled with the compost. This is made moderately firm by pressing it with the fingers; it is then moistened by holding the receptacle in a pail of water (Fig. 3). The water must not come above the rim of the pot because it is necessary that the moisture should rise up through the compost. As soon as the surface of the soil becomes damp, the pot is set aside to drain for a few hours before seed sowing is com­menced. The seeds are sown thinly (Fig. 4) and covered with the sifted compost. The depth to which the seeds are covered depends on their size. Very fine seeds, such as those of Begonia, require only a fine sprinkling of silver sand, whereas larger seeds should be covered to the depth of their greatest dimensions.

When the seeds have been sown, the receptacles should be covered with panes of glass and shaded with sheets of paper (Fig. 5).

Fig. 5. The glass tilted with a label to give air to the seedlings

Each day the glass should be reversed to prevent the con­densed moisture from dripping on to the soil, and setting up decay. As soon as the seedlings appear, however, the paper covering must he removed and ventilation of the receptacle begun. The glass covering should therefore be tilted slightly. This is conveniently done by means of the plant label, and the amount of air is increased in this way until the covering can be removed altogether.

Pricking Out the Seedlings

As soon as the seedlings have developed their first true leaves they are pricked out ½inch apart in pots of fertile compost such as John Innes Potting Mixture No. 1, and immediately watered in. They are shaded from bright sunlight until they are established. This generally takes 7-14 days, after which they are given more light and air.

The First Potting of the Seedlings

Before the seedlings show signs of becoming overcrowded they must be set singly into 3 or 3½-inch pots, watered in, and again shaded until established. These plants can then be treated in the manner described in Chapter 6.

Propagating 'Cuttings' in Bottles of Water

A very simple method of obtaining young plants of Codiaeum (croton), Coleus, Dracaena, Fuchsia, Nerium and Tradescantia is by inserting 'cuttings' in bottles of water.

The 'cuttings' are taken in the usual way, by severing them just below a node (where a leaf is inserted in the stem). They are then fixed in the mouths of small-necked bottles where they remain suspended. The bottles are filled to within a fraction of an inch of the top of the necks with water, preferably rain water.

To prevent green scum (algae) forming in the water, it is best to place a few small lumps of charcoal in it.

If this operation is done in the spring, the bottles of 'cuttings' can be set on the window-sill, and roots will form in a few weeks. Potting must be done immediately roots begin to form.

Hormone Preparations for Plant Propagation

Hormone preparations or growth-regulating substances are organic compounds specially prepared for speeding the develop­ment of roots on 'cuttings'.

Although the 'cuttings' of many kinds of plants can be rooted without the use of hormones, roots are produced more quickly by their aid. This is specially important with slow-rooting plants such as species otErica and Azalea.

Growth-regulating hormones can be purchased from horti­cultural and chemists' shops and are easy and safe to use. The products are obtainable in liquid or powder form, and full directions for their use are supplied with the preparations.

Striking 'Cuttings' with Hormones using Polythene Film

The 'cuttings' are prepared in the usual way by severing them just below a node and removing some of the lower leaves with a sharp knife. The cut ends are dipped in a hormone-rooting powder and then wrapped in a wad of Sphagnum moss, which has been thoroughly moistened. Finally the mossed ends of the 'cuttings' are enclosed in small squares of polythene film to keep the bases of the 'cuttings' moist until roots have been formed.

These prepared 'cuttings' can then be packed closely together and set in an upright position on a shallow box or seed pan. They should be placed in a propagator or a glass-covered box where they can remain until they have rooted sufficiently to be potted up separately.

Propagation with Polythene Bags

This is an ideal method to use in the home for it can be done without the aid of a propagator. The bags are obtainable from shops as they are often used to keep food in a fresh condition. The 'cuttings' are treated with hormone powder and inserted in small pots of sandy soil in the usual way. The pots of 'cuttings' are then slipped into polythene bags, the tops of which are secured with rubber bands. The pots of 'cuttings' can be set on a window-sill in a warm room until they are ready for potting up separately.

Hormone Treatment for Air-layering

Air-layering is a method which can be adopted to increase plants with woody stems which do not root readily from 'cut­tings'. The principal house plants propagated in this way are Azalea, Cissus, Codiaeum, Fatsia, Philodendron and Rhoicissus.

The operation is performed by slitting the stem on one side to form a tongue at the point where it is desired to produce roots. The tongue is then dusted with a hormone powder, damp moss is packed into the slit and the 'layer' is covered with moss. In order to prevent the tissues from drying, the moss wrapping is covered with polythene film. This operation is best done during the summer months when growth is active.

When sufficient roots have formed, the shoot is cut off and set in a pot of suitable size.

Propagation by Ringing

This method is so called because it consists of removing a ring of bark from the stems of plants at the point where it is desired to produce new roots.

Ringing is performed on plants which lose their lower leaves and become too tall and unsightly ('leggy'). The principal house-plants which need this treatment are Codiaeum (croton), Cordyline, Dracaena, Fatshedera, Fatsia, Monstera and Philodendron.

The best time for 'ringing' is early spring when active growth is beginning. A ring of bark about \ inch wide is removed just below the low­est leaves. The ringed stem is then bound with moss (Fig. 6) and covered with polythene film. The film keeps the moss moist until sufficient roots are formed, when the rooted top portion can be cut off and set in a separate pot.

Many of the ferns which are used as house plants can be increased by sowing spores. The spores are formed in clusters, usually on the backs of the mature fronds. The clusters of spores arc mostly brownish in colour. To ascertain if the spores arc ripe and ready for sowing, the fronds should be gathered, placed in a paper bag and hung up in a warm room for a few days. By that time the spores will have dropped into the bottom of the bag and will be in the form of a brownish powder.

Fig 6

A flower-pot should then be filled with potting soil covered with a thin layer of finely sifted peat. The spores may then be sprinkled thinly on the surface (a tiny pinch is sufficient for a 5-inch pot), the pot covered with a pane of glass and placed in a saucer of water. If the pot is set in a warm room, the top of the compost will be covered with a green somewhat moss-like growth in 4-6 weeks. This growth will consist of the prothalli, which are small, flat, heart-shaped structures bearing the male and female organs. After fertilisation has taken place, new fern plants will appear. These young ferns can be pricked out, in the same manner as seedlings of other plants, into a light fertile soil. After they have been pricked out in a pan or another seed pot, they must be set in a saucer of water and again covered with a pane of glass. Eventually the plants can be put into separate pots. The next step is to place these plantlets in a glass-covered box, where they can remain until well established, when the glass can be removed and the plants acclimatised to the atmosphere of the room.

The principal room ferns raised in this way are Adiantum, Cyrtomium, Davallia, Nephrolepisand Pteris.

Propagation by Leaves

Fig. 7. Leaf of Begonia rex (right); young plants developing on the severed veins (left)

It is possible to raise many house plants by using leaves or portions of leaves as 'cuttings' and this method is generally used with plants which do not produce shoot 'cuttings' freely. The principal plants increased in this way are Begonia Gloire de Lor­raine, Begonia rex (Fig. 7), Gloxinia, Saintpaulia and Streptocarpus. There are various methods adopted, but in most cases a matureleaf is used. This is usually prepared by cutting notches just below the junctions of the main veins. The leaves are then laid, underside downwards, on the surface of a pan of sandy soil. The pan is covered with a pane of glass, and set in a warm room or greenhouse, in spring or early summer. Young plants appear just above the notches; when large-enough, these are detached and treated as seedling plants. Saintpaulia is propagated by detaching the leaves and treating   them   as    'cuttings' (Fig.   8);   the   bases   of the leaves are inserted just below the compost. As already stated, there are many kinds of plants which can be raised from leaves but which are not usually propagated in this way because 'cuttings' or seedlings are more easily obtained.

Other plants which can be raised from leaves are Coleus, Fittonia and Fuchsia.

Increasing House-Plants by Division

All house-plants which produce rhizomes (underground, creep­ing stems) or numerous crowns or offsets may be increased by dividing these structures and setting the divided portions in separate pots. This operation is best done in spring, or when new growth is beginning. Before division is started the compost must be prepared and the requisite number of flowerpots obtained and provided with drainage materials. On the day before the plants are divided, the soil must be given a good soaking with clean water, or the dry soil will drop from the roots when the plants are divided.

When everything is ready, the plants should be removed from the pots by holding them upside down and tapping the rim of the pot on the edge of a bench.

All crocks are next removed with a pointed stick and the plant separated into portions of the required sizes. It will be found that some plants can be divided by breaking the balls of soil into sections whilst some will have to be divided by cutting through the rhizomes or crowns with a stout knife.

In all cases each separated portion must have one or more shoots and a number of healthy roots.

When potting up these divisions, set them in pots which are just sufficiently large to accommodate the roots without cramping. Then make the compost firm and water it, using a can fitted with a fine rose.

Fig. 9. Maidenhair Fern (Adiantum cuneatum) divided for potting

This operation of dividing is always a great disturbance to the plants, and special care is needed until the roots penetrate the new compost. To encourage root development, the plants must be kept in a cool, shaded position and the leaves mois­tened two or three times during the day. This is done cither by syringing them or by sponging the leaves with clean water. After a few weeks of this treatment, the plants may be returned to their normal positions.

Plants Easy to Propagate by Division

Fig. 10. Grafting a cactus plant Fixing scion to stock with a thorn

Adiantum (Fig. 9), Aspara­gus, Aspidistra, Billbergia, Chlorophytum, Clivia,    Iso-lepis,     Liriope (Ophiopogon), Miscanthus, Pilea, Ptcris, Saintpaulia, Sansevieria, Saxifraga.

Propagation of Cacti by Grafting

Although it is easy to graft many kinds of cacti, grafting is not generally practised on all types because it is unnecessary. The principal cacti treated in this way arc Aporocactus and Schlum-bergera. These have pendent shoots and their flowers arc shown to better advantage when the 'head' of shoots is developed on the top of the tall rigid stem of the stock plant. Grafting on to these stocks also gives the plants more vigour.

To prepare the stocks they arc cut offhorizontally at the desired height and then slit downwards to ½ inch in depth. The graft, a portion of stem about an inch in length, is inserted in the cleft (Fig. 10), which is closed by pressing the sides together and may be secured by means of a thorn. Various types of cacti are used as stocks for grafting. One of the most popular of these is Pereskia, but Opuntia robusta and others are also used for the purpose. As these plants are of a succulent nature, the grafted stocks do not need a propagating frame and may be set on a window-sill where a union of stock and scion will quickly take place.

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