A scientific rundown of stem propagation

stem propagation

This guide explains how to take stem cuttings and the science behind propagation. Scroll down for five stem propagation methods. 

How does stem propagation work?

Once severed from the main plant, and given the right conditions, certain parts of plants will grow a new root system so that it eventually becomes an independent organism. New root tissues put out by plant cuttings are called adventitious roots. The term refers to any new root tissues that emerge from the stems or leaves of a mature plant, rather than from an existing root system or within a plant embryo. 

Putting out adventitious roots is a process of regeneration. By forming its own root system, the cutting attempts to independently acquire the nutrients and moisture that it no longer receives from the mother plant. Mature, woody cuttings put out adventitious roots less readily than young, supple green cuttings.

Plant growth hormones auxin and cytokinin are responsible for the formation of adventitious roots. Root tissue formation occurs when there is proportionately more auxin to cytokinin in the part of the plant where it has been severed. Rooting powders encourage root formation because they contain auxin. Although the major naturally occurring auxin is indole 3-acetic acid, many different synthetic auxins have been developed. Plants vary in their capacity to put out new roots because auxin to cytokinin levels are influenced by day length and season. 

Interestingly, plant cuttings ‘know’ which end was closest to the roots while it grew on the mother plant. When cuttings are taken from the mother plant, auxin will move towards the end of the cutting that was growing closest to the ground, accumulating there to form new roots.

How do you take stem cuttings?

Stem cuttings should be four to six inches long. Stems that are green and supple will be easier to root than stems that are woody. Take stem cuttings by using a sharp, clean knife or pair of scissors and cutting just below a node. Nodes are parts of the stem where new shoots and leaves emerge. They often look like knobbly joints or raised rings around the stem. The best time to take cuttings is in the early morning, when plants are most turgid. 

Strip the stem cutting of its leaves except for the top third of the cutting. If the plant has large leaves, cut them in half. Reducing the surface area of leaves will prevent the cutting  losing moisture through transpiration while it is rooting.  

The portion of the plant you take cuttings from should be healthy, free of discoloration or wilt. Ideally you should be taking stems that are displaying signs of active growth - for example, if you see a new shoot or bud growing on it.

Lateral shoots, which grow from the side of a main stem, usually propagate better than terminal shoots, which are part of the main stem. See the diagram below for the difference between lateral and terminal shoots. Stem cuttings taken from the end of a stem are usually better, though you can use other parts of the stem. 

Terminal lateral shoots

Lateral shoots grow off the side of a main stem. They are usually easier to propagate than terminal shoots on the main stem. Anne Bebbington https://www.flickr.com/photos/71183136@N08/6949769502

Plants that propagate from stem cuttings 

Philodendron 

Golden pothos

Geranium 

Azealea 

African violets

Tradescantia 

Crassula pellucida

Ficus elastica

Ficus benjamina

Schlumbergera truncata

Hibiscus

Monstera 

Prayer plant

Most herbs - oregano, basil, lavender

Ficus cutting

Ficus  benjimina stem cutting that has rooted in water. This root system is now well-developed enough for the plant to be potted. Biusch https://commons.wikimedia.org/wiki/File:Ficus_cuttings_with_roots_in_a_bottle,_White_background.jpg

Should you use rooting powder on cuttings?

Rooting powders or Keiki paste contains growth hormones that make the rooting process quicker and more reliable. These substances are applied to the ends of cuttings, where the roots will grow. You can also try honey or cinnamon powder to boost rooting.

Rooting hormones are not strictly necessary - with the right conditions, plants can put out new roots without them. 

What is the best rooting medium for propagation? 

The rooting medium is any material into which leaf or stem cuttings are inserted. 

Most propagation guides advise you to insert cuttings into sandy soil. This is actually a less reliable rooting medium than sphagnum moss, water, or perlite. Sphagnum moss and perlite retain moisture but also hold a lot of air pockets that prevent cuttings from rotting.  

Different species will root better in different mediums. Experiment with several mediums at the same time for comparison.

Should you add fertilizer to water used for propagation?

For propagation methods where the plant cuttings are actually in contact with water (methods 2 and 3 below), you can add a miniscule amount of fertilizer to the water.

Once severed from the mother plant, cuttings still seek out nutrients. Providing them with too much fertilizer will discourage the plant from putting out adventitious roots since it can absorb all the nutrients needs via the cut on the stem or leaf. 

One drop of balanced fertilizer per 500 ml is enough. Never add fertilizer in the concentrations advised on manufacturer packaging - they will be too much for propagation purposes.  

How long does it take for cuttings to form roots?

People often underestimate how long it takes plant cuttings to form new roots. You might begin to see roots as early as seven days after insertion into the medium, but it will likely take longer. The speed at which roots appear will depend on whether it is the plant’s growing season and how much humidity and sunlight the cuttings receive.

When should you plant cuttings in their own pots?

You should wait until roots are two to four inches long before transferring the cuttings into their own pots with a potting medium. Many succulents and cacti do very well in just perlite, so you may not need to change the medium at all for these. 

Five propagation methods for leaf and petiole-and-leaf propagation

Method 1. Humidity propagation

A very effective method for stem cuttings

Irene Campi https://miro.medium.com/max/1800/1*PBYUE-_F6bbwFqhSyO54qw.jpeg
  1. Wet the cut ends cuttings then dip them into rooting powder.
  2. Get a clean, clear container and fill it up half-way with water.
  3. Cover the top of the container with cellophane. Make the cellophane taut by binding it with rubber bands around the neck of the jar 
  4. Puncture small holes into the cellophane close to the rim of the container using a pin 
  5. Carefully ease the bottom third or of cuttings into the holes. Prop the rest of the cutting upon the rim of the jar so they don’t fall in. The bottom of the cuttings should not touch the water
  6. Ensure there is no gap between the cellophane and the cutting where the cutting penetrates the cellophane so that humidity cannot escape from inside the container 
  7. Place in indirect sun

Method 2. Water propagation

This is the simplest propagation method but it is not always reliable. Works best for petiole cuttings during the height of the growth season. Give your cuttings lots of indirect sunlight to maximize the effectiveness of this method.

Kaylin Pacheco unsplash.com/photos/rYD43LAD--s
  1. Get a clean jar or bottle and fill it partially with water
  2. Place petiole cuttings into the water so that the water comes up to around a third or quarter of the petiole 
  3. Place in indirect sun

Method 3. Combined humidity and water propagation

A combination of methods 1 and 2: cuttings sit in the water and the container is covered in cellophane so that the whole cutting (not just the tip) is sealed in a humid chamber. Works for petiole cuttings.

    1. Get a clean, clear container that is taller than the length of your cuttings 
    2. Fill a quarter or third of the container with water
    3. Place petiole cuttings into the water so that the water comes up to around a third or quarter of the petiole
    4. Cover the top of the container with cellophane. Make the cellophane taut by binding it with rubber bands around the neck of the jar 
    5. Puncture small holes all around cellophane. The idea is to trap some humidity inside the jar to encourage rooting but also to let some air in to circulate around the cutting.
    6. Place in indirect sun

Method 4. Sphagnum moss propagation 



Dendroica cerulea https://www.flickr.com/photos/dendroica/2177851606
    1. Soak sphagnum moss in a bowl of water for a few minutes. 
    2. Remove the moss and squeeze hard to remove excess moisture. Too much moisture and the cuttings will be liable to rot. The moss should be only slightly damp. 
    3. Fill a cup with sphagnum moss, insert the tips of cuttings lightly into the moss 
    4. Bag the cup up inside a plastic resealable container
    5. Place in indirect sun

Method 5. Perlite propagation 

Works for leaf or petiole cuttings

Dawn Easterday https://www.flickr.com/photos/7998285@N08/497108811
  1. Place perlite in a bowl. Add enough water to moisten the perlite slightly. 
  2. Place the moistened perlite in a container 
  3. Insert tips of cuttings lightly into the perlite. You might need to make room in the perlite for the cuttings with a stick first.
  4. Place in indirect sun

After you’ve prepared your cuttings using one of the above methods, give your cuttings as much indirect sunlight as possible, for example, next to a south-facing window with net curtains. Adding growth hormones like rooting powder or Keiki Paste will also help. Increase humidity around cuttings by placing their container inside a tray full of pebbles with water coming up to half the depth of the pebbles.

 

 

Leave a comment

Name .
.
Message .

Please note, comments must be approved before they are published