There are many reasons to consider propagation in one of its forms: if a plant has outgrown its allotted space; if it is looking old and jaded; if someone has asked for a cutting; or simply for the challenge and satisfaction of producing a thriving new plant.

The two basic ways to produce a new plant from another are asexually (vegetative propagation) or sexually (seed). Seed is plentiful, but the results are variable, and may differ quite considerably from the parent plant. Vegetative propagation takes up more room and may be slightly slower, but it gives consistently similar results to the parent.

Vegetative propagation

This is by far the most common means of propagation for indoor plants, and it includes propagation by cuttings (stem, leaf, and root), division, layering, offsets, plantlets, and air-layering. Each technique relies on using part of the parent plant to produce the new one, without necessarily detaching it first. The offspring is genetically identical to the parent, and its growth pattern should also be identical.

Cuttings

“Roots, leaves, stems, and shoots can all be used to produce new plants.”

Taking a cutting means removing part of the parent plant in order to grow a new one. After the piece is severed, its supply of moisture from the parent’s roots is cut off, so an adequate level of moisture must be maintained while the cutting produces its own roots to replace the loss.

Some plants produce roots so easily that the cutting can simply be placed in a container of water. Others need the stimulus of a rooting hormone in either liquid or powder form to produce roots. Spring and summer are the best times to take cuttings, because the plant is actively growing and light levels are high. Avoid taking cuttings when the plant is in flower, because flowering shoots will not root successfully, wasting soil, time, and the cutting itself.

This technique involves taking a whole leaf —plus its stalk —from the parent in order to produce a new plant.

Plants such as peperomia and saintpaulia can be propagated by taking a whole leaf and its stalk (petiole). Select an undamaged, fully opened leaf, remove it from the plant, and trim the petiole about 1 in. (2.5 cm) below the leaf. Insert it into moist pot ting soil at an angle to shed water from the leaf anti produce a straighter plantlet. Support a plastic cov­ering with canes so it does not touch the leaf.

• Using a clean knife, remove the petiole at the base, then trim below the leaf.
• Insert, the cut edge at an angle into moist, free-draining soil, and cover with plastic.
• New plants will form at the base of the petiole. Separate and pot into fresh soil mix.

This technique involves using whole leaves taken from the parent to produce new plants.

Whole leaves of succulents, such as crassula, echeveria, and sedum, can be used to form new plants. Take a large, healthy, mature leaf, and leave it to dry for 24 hours before planting. This reduces moisture loss caused by excessive “bleeding.” Push the cut end of the leaf into the moist soil. Do not cover the pot with plastic, since succulents are liable to rot. Begonia rex can be propagated by tak­ing a whole leaf and making slits through each of the main veins. The leaf is weighed or pegged down to ensure it remains in close contact with the soil and covered with plastic.

• Remove a healthy, mature leaf with a clean, sharp knife and make small cuts across the veins on the underside.
• Lay the leaf face-up on moist soil and hold down with small stones or hoops of wire. Cover with plastic.

Vein cuts

New plants should form at each of the small vein cuts. These can later be separated and potted up.

This technique involves cutting a whole leaf in half or into several horizontal sections. It is a simple and effective way to produce a number of new plants.

The leaves of sansevieria can be cut into horizontal sections about 2 in. (5 cm) deep. Keep them the same way up that they were growing, and insert them into moist soil to one-third of their depth. Two or three plantlets should form from each sec­tion.

Streptocarpus leaves can be cut in half length­ways along the midrib or cut into V-shaped sections horizontally. New plantlets should form along the cut surfaces.

• Use a clean, sharp knife to remove a healthy, mature leaf from the parent plant. Cut along the length of the central vein (midrib).
• Lay the leaf down lengthwise, pressing the cut edge lightly into the moist soil.
• New plants should form along the cut edge. These can be potted up individually.

Young plants can produce roots at every-leaf node along their stem, although not all plants retain the ability- to do this easily as they mature.

The formation of roots is triggered when the hor­mones in a cutting respond to stress. These hormones are concentrated in the growing tip, but can also be found in each leaf node. The younger the plant, the greater the chance that almost any part of the stem will root if there is a leaf node present.

Stem

Some plants root so well that a growing tip on the cutting is not necessary. From a long shoot it is possible to take the tip cutting, then cut the rest of the stem into similar lengths, making each top cut just above a leaf node, and each bottom cut just below a leaf node.

Heel

Short side-shoots of 3—4 in. (7—10 cm), taken as ti j cuttings, can be pulled from the stem complete with a “heel” of bark attached. This strip should be trimmed down to a short point with a sharp knife, to prevent it rotting.

Cane

Plants such as cordyline, dieffenbachia, dracaena, and yucca, which form strong, woody stems, can be propagated by cutting one of their bare stems into several pieces, each 2—3 in. (5—7 cm) long. The pieces are laid horizontally onto the soil or inserted vertically into it. If they are vertical, they must be placed the same way up as they were growing on the parent plant.

Tip

Remove the end of a shoot, including the growing tip and at least 3—4 in. (7—10 cm) of the stem. Trim the cut end under a leaf-joint (node), and remove the leaves from the lower third of the cutting. Dip the very end of the cutting in rooting hormone and tap off the surplus. Insert the cutting into a pot of moist soil by pushing it in to ensure that there is a good contact between the stem and the soil.

Alternative rooting methods

While some plants root easily, others need help in the form of rooting preparations designed to enhance the natural hormones that promote root formation.

Rooting hormone, available in powder or liquid form, is designed to mimic the action of the plant’s natural hormones and boost the rooting process. Not all plants need it — for example, geraniums tend to rot if it is applied.

The preparation should be kept clean to prevent it from deteriorating, so only pour a small amount into a shallow container, and discard the remainder once the cuttings have been prepared. Never c ip the cutting directly into the pot. The powder is quite powerful, and is needed only on the cut surface, so make sure you dip only the very end of the cutting into the powder and tap off any surplus.

Rooting in water

Many plants, especially those with fleshy stems, root easily in water.

They can be transferred to a soil mix as soon as the roots appear.

This technique is low-risk, since it is the only one that does not involve separating the new plant from its parent until rooting is complete.

The advantage of layering is its lack of risk to either the parent plant or its offspring. The young plant, or the stem to be layered, is bent down and brought into contact with a pot of soil without detaching it from its parent.

It is held in position with a U-shaped wire hoop, and remains there until it has formed roots to support itself; the connecting stem can then be severed. If rooting is unsuccessful, the stem is not cut, and the whole process can begin again. Indoor plants, such as hedera and philodendron, which have aerial roots at leaf joints on the stems, can be propagated in this way.

Self-propagating plants

Plants such as chlorophytum and tolmiea produce small replicas of themselves, complete with tiny roots, on long stems or mature leaves as they grow. These are ready to start growing as soon as they come into contact with the growing medium. The plantlets can either be rooted while they are still attached to the parent plant or they can be separated, potted up, and grown on in their own right with a minimum of fuss as they establish.

In fact, the only difficulty may be with the sheer quantity of the offspring produced — although there is no need to remove them from the parent plant, where they can remain indefi­nitely. If the plantlet already has some roots of its own, it can either be detached from the parent plant imme­diately and rooted in water, or planted immediately in small pots of soil mix. The roots should take only a few days to begin supporting the plant.

Offsets

Offsets are small plants that develop at the base of mature plants, such as bromeliads, cacti, and succulents.

These small plants either grow from the main stem itself, on secondary stems (stolons) or they arise base- to-base, such as bulblets.

No offset should be severed from the parent plant until it is large enough to survive on its own, and although this is not always easy to judge, it can generally be taken once it resembles the par­ent plant in shape and characteristics. It may even develop roots of its own before it is severed, which makes success even more likely.

Use a sharp, clean knife to cut the offset from as close to the parent as possible, and place it into a pot of moist potting soil. Larger offsets may be unsteady, and need supporting with short canes until the roots provide firm anchorage.

Such plants as lily and amaryllis can produce miniature bulbs on the stem, offsets from the base, or extra scales that can be separated from the parent.

Many plants that arise from bulbs reproduce themselves as miniature bulbs as well as by seed. The small bulbs reach maturity much more quickly than seed, tut lack the variation. Those that arise in the leaf axils on the stem are known as bulbils; those that arise at the base, or are cultivated by breaking he scales from a lily bulb, are called bulblets.

• Remove and discard any damaged scales from the outside of the mature bulb. Take health ones by breaking cleanly as near to the base as possible. Up to 80 percent of the scales can be taken arm the bulb will still flower.
• Place he plastic bag of moist soil, fold to close, and keen warm and dark for 8-10 weeks.
• Tiny white bulblets with delicate roots will form at the base of each scale.
• Scales can be cut lengthwise to separate bulblets, leaving each a piece of scale as food.
• Pot several bulblets together for the first year. The leaves will initially resemble grass.

Many clump forming plants can be increased in number by dividing the existing large clump into smaller ones.

This technique is suitable for any houseplant that forms a clump as it matures, such as cacti, orchids, ferns, chamaedorea, maranta, saintpaulia, and sansevieria. It is particularly straightforward when the plant has distinct rosettes, such as saintpaulia, sepa­rate upright stems, such as chamaedorea, or distinct pseudo bulbs, such as orchids.

Start by removing the plant from its pot and laying it on a flat surface to examine it. (Watering the plant ar. hour before removing it from its pot will enable you to remove it more easily.) Select a point where separation looks possible and gently begin to tease the roots apart. It may be necessary to wash t! e roots first to get a clearer view, but it is important to inflict as little damage as possible to the roots, since this will hinder their recovery.

Plants with a rhizomatous or very dense root sys­tem, such as orchids, may need to be severed with a knife, so make sure that it is clean and sharp, and the cut is made in as few movements as possible. For the greatest chance of success, each piece of plant should have both leaves and roots. The new plants can then be planted into separate pots slightly larger than their root system, and watered to set tie the potting soil around the roots.

The production of seed is nature’s way of ensuring a continuing mix of genes to give strong, healthy characteristics.

Unlike plants that are grown from cuttings, which are clones of the parent, plants grown from seed can bear characteristics of ancestors going back several generations, rather than just the parents, so the exact appearance of the offspring is very hard to predict.

It is less common to grow indoor plants from seed than outdoor varieties, because so many more are produced than can normally be used, although the surplus can always be given away or exchanged. The attraction is the chance to grow something exotic, such as an avocado or citrus, from a seed which might otherwise be discarded, and this can be a fun way to interest a child in the process of growing. For the keen cook, it is also easy to grow sprouting beans, and herbs like basil and parsley, from seed in a succession of small usable batches to ensure a regular, manageable supply.

For the majority of seeds, germination is trig­gered as soon as they are sown into soil and begin to absorb moisture through the seed coat. However, some seeds have a particularly hard or moisture- resistant seed coat and need a little help before the process of germination can begin. The key is to carefully break through the outer layer of the seed bcoat without damaging the embryo inside. The easiest way to do this is scraping or “scarifying” the seed with an abrasive, such as sandpaper, or chip­ping away a tiny sliver of the seed coat with a clean, sharp knife.

Fine seed should be sown broadcast — sprinkled on the surface — because if buried too deep, it will run out of energy before it reaches the surface.

Seeds have only a limited food supply to last until they form roots and begin to photosynthesize. If they are buried too deep, they run out of food before the y reach this stage and die.

The easiest way to handle extremely fine seed is to mix it with silver sand before sowing, so that it can be seem. As with any seed, always be guided by the instructions on the seed packet regarding the depth at which to plant the seed, as well as whether it should be covered.

If there is no packet, the general rule is that the smaller the seed, the less covering it needs; very fine seed may need no covering at all. After sowing, cover the? pot with a plastic bag, held securely in place with a rubber band, or place a sheet of glass over the seed tray. Place in a shady spot at a temperature of approximately 60—70°F (15—20°C) until germination occurs.

Aftercare

Remove the covering when germination starts, and transfer to a bright situation, out of direct sunlight. Turn regularly if the light is lopsided, to prevent the seedlings becoming drawn and bent. As soon as the young plants have two ‘true’ leaves (which appear after the first “seed” leaves), they can be pricked out into small, individual pots of soil. Handle by the leaves at this stage, not the stem, because bruising the stem now will kill the plant. Settle by watering gently, rather than pressing the soil with fingers or a dibble, because this can damage the roots.

Spores

Select a mature frond with sporangia on the underside and check the ripeness of the spores by touching them gently — a dust-like deposit on the finger indicates that they are ready. Detach the frond with a clean, sharp knife and lay it face-up on a piece of clean, white paper, where any activity is clearly visible. Keep in a warm place for a day or two, so plenty of spores are shed.

Sow the spores onto moist, sterile soil, enclose in a plastic bag, and place in a warm position with plenty of bright light, but not direct sun. Mist twice a week with sterilized water (boiled and allowed to cool) until the soil is covered with green “moss (this takes approximately 6—12 weeks). Prick out small pieces of “moss” onto sterile soil and mist with lukewarm boiled water.

Finally, seal into plastic bags and keep them in a warm, bright place, misting daily, until tiny ferns develop. These can be transplanted as soon as they are large enough to handle.

Pricking Out

The process of loosening the growing seedlings and transplanting them from their seed tray into individual pots is called “pricking out”. Gently grip the seedling by the leaves and use a dibble to plant it into fresh soil.

• To sow very fine seed, fill a pot or seed tray with seed and cutting soil. Level the surface by scraping off the excess with a straight edge across the rim.
• Use a hoard to firm the soil vet y gently and create a level surface.
• Sieve a fine layer of soil over the top to form the seedbed.
• Sprinkle pinches of the seed-and-sand mix evenly onto the soil.
• Water by standing the tray inside a larger one containing water.