Garden trowel next to three young plants.

What You Need to Know About Plants Propagation

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.


Leaf petiole cutting.

Propagation – Leaf Petiole Cuttings

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.

Plants with roots sitting in the grass.

Propagation – Division

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.


Plants in different period of their growth.

What You Need to Know About Seed Propagation

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.

 

Providing The Right Conditions

Some seeds germinate readily with little or no help, but others are more fussy and require the correct conditions to grow.

Humidity Temperature Light Soil mix
A moist environment

will prevent the leaves of young seedlings losing water, which cannot be replaced until a good root system has formed. A

propagation case is ideal, but a plastic bag sealed around the pot works just as well. When the seeds establish, you may need to support the plastic bag on short canes to prevent it touching the leaves

(which can lead to

rotting).

Most seeds grow well in a temperature of about 65°F (18°C), but some require higher tempera­tures in order to germi­nate successfully. A heat­ed propagation case will maintain a constant tem­perature. These come in various sizes, according to how many seeds (or cut­tings) are to be grown. Wean the young plants before they leave the case by gradually lowering the temperature. Once germination occurs, the seedlings will need to be placed in a brighly lit position, out of direct sun. Too much direct sun­light will scorch the deli­cate new leaves, while too little sunlight will cause the seedlings to become tall, weak, and spindly. This is also a problem ‘if too many seedlings are left too close together in the seed tray for too long, because they are competing for light. Seedlings grow best in a light and free-draining soil mix that does not contain much fertilizer.

To sterilize pots of pot­ting soil (for example, for spore sowing, see page 102), fill a small pot with seed soil mix and firm gently. Lay a piece of paper towel on the sur­face and pour boiling water through until it comes out of the drainage holes at the base. Let cool before use.


Man planting seeds in the ground.

Propagation – Sowing Fine Seed

Fine seed should be sown broadcastsprinkled on the surfacebecause 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.

Small plants in cubic soil.

Propagation – Sowing Small Seed

This technique is suitable for any seed that is large enough to be handled individually. Citrus seeds are ideal.

Some plants can be raised indoors purely for fun and for the satisfaction gained from the sight of a new shoot emerging from the soil. Citrus seed — from oranges, lemons, and grapefruits — is ideal for children to experiment with, because it is free and would otherwise be thrown away. It will also germinate fairly quickly, producing an attractive plant with fragrant, glossy leaves.

Unfortunately, it is unlikely to produce fruit, since the conditions may not be suitable, although citrus plants are certainly worth growing for their foliage alone. You will need to plant several seeds to ensure that at least one healthy plant grows on.

  • The pips from oranges, lemons, and grapefruits are all easy to grow and quick to germinate in spring and summer. Sow fresh from the fruit or keep in water until you are ready to sow them.
  • Fill a pot with soil and space the seeds evenly on the surface. Press them in carefully to twice their depth.
  • Water with a fine spray to settle the soil, then keep warm and moist. Germination will take about 6—8 weeks.

Young plants in pots on a large metallic tray.

Propagation – Sowing Large Seed

There are few really large seeds that are grown for indoors. Coconut and avocado are the exceptions.

The main advantage of large seed is that it is easy to handle, since it does not need mixing with sand or thinning out if too many seedlings germinate. In fact, large seeds can usually be sown into individual pots of soil large enough to support their growth for several weeks, eliminating the need to transplant the seedlings and risk them suffering a check in growth as a result of the shock.

Coconut is the largest seed grown for indoors, but as it is impractical to plant in the home, garden centers usually sell seed that has already been germinated. Avocado and date pits are good to experiment with, since they would otherwise be thrown away — there is nothing to lose by sowing them, and possibly a nice plant to gain. Both can be soaked in water first to maintain the moisture levels inside the seed if they cannot be sown immediately.

Be patient with larger seeds after sowing, because they may take some weeks to germinate. Keep the seed warm and the growing medium moist until the first shoot appears.

  • Take an edible fruit and carefully slice it open with a clean, sharp knife. Ease the “pit” out of the middle with a teaspoon or blunt knife, being care­ful not to cut into it.
  • Push the blunt end of the pit into a pot of soil, leaving the pointed end slightly exposed. Water to settle the soil, then keep warm at 65°F (18°C) until a shoot appears.

Succulent plants leafs sitting on the ground.

Propagation – Whole Leaf Cuttings

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.


Scissor sitting on a few leafs.

Propagation – Part-Leaf Cuttings

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.

Man holding a young plant in his hand.

Propagation – Stem Cuttings

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.