A popular method of producing new plants from existing ones is by taking cuttings. Depending on the time of year and the plant, tree or vine being propagated, we can take hardwood cuttings from older wood, or softwood cuttings from newer, more pliable growth.
Rather than describe the process for propagating cuttings here, detailed propagation instructions can be found in the following articles:
- Propagation of hardwood cuttings which are done in autumn to winter, during dormancy, when all leaves have fallen from deciduous plants.
- Propagation of softwood cuttings which are done in spring to summer, during the growing season for evergreen plants.
Treating cuttings with rooting hormone can increase the chances of stimulating root growth. This is more critical in plants that are more difficult to root.
There’s not much to using rooting hormone products, we simply dip the base of the prepared cutting into the rooting hormone, which can come in the form of a liquid, gel, or powder, and that’s all! After that the cutting is inserted into a suitable propagating medium and moved to a protected location to grow new roots.
Which Natural Products Can Be Used to Produce Roots in Cuttings?
It’s possible to make our own natural rooting hormone, see article – How to Make Home Made Plant Rooting Hormone – Willow Water. I’ve made willow water before, and in my experience, it works really well!
Another natural product that gardeners have been using to stimulate root growth in cuttings that doesn’t require any preparation is regular honey – yes, you heard right!
Recent studies have shown that while honey was not as successful as synthetic plant rooting hormone, with many plants it significantly increased the percentage of cuttings that produced roots, and the amount of root development.
- Dunsin et al., (2014) used honey in an experiment, as an alternative hormone on Parkia biglobosa. Cuttings treated with honey showed a greater total number of roots, greater total root length and a lower mortality rate then the untreated control cuttings.
- Firth, (2018) reported honey can be used for treating Hemigraphis cuttings and it showed higher percentage of rooting (94%) vs untreated control (88%) and heavier roots (4.08g) vs unteated control (2.22 g).
- Uddinet al., (2020) found that grapevine cuttings treated with honey produced a greater number or roots and root length than untreated controls, with increased cutting survival rate (84.3% vs 73.3%).
Considering that honey is so readily available, relatively cheap, and how well it increases root growth compared to not using it, it’s definitely worthwhile to use when propagating plants from cuttings.
How to Use Honey to Treat Plant Cuttings for Propagation
To use honey as a root growth stimulant:
- Dip the cut ends of the prepared cuttings into a small amount of honey, making sure the honey coats the cut ends evenly. This allows the honey to come into direct contact with the plant tissues to potentially provide the best benefits for rooting.
- Plant the cuttings, insert the honey-dipped ends of the cuttings into a suitable propagating medium, ensuring that the cuttings are inserted deep enough (one-half to two-thirds of their length) to provide stability but still allow the leaves or buds to be above the medium.
It is not necessary to soak the cuttings in honey or dilute the honey with water. Soaking the cuttings in a honey-water solution may dilute the concentration of beneficial compounds and sugars in the honey, potentially reducing its effectiveness.
Using boiling water to dilute the honey, as some suggest, is also a bad idea. Honey contains many enzymes – these are compounds that are produced by living organisms that act as a catalyst to bring about specific biochemical reactions. Many enzymes and other organic compounds (carbon-containing substances) in honey do not survive high temperatures and will be degraded at 100 °C (212 °F), the temperature at which water boils.
- The study by Firth et al., (2017) followed a method which came from a general gardening website, without any authoritative sources, and without explanation for this method. The honey treatment was made from 2 cups of boiled water mixed with 2 tablespoons of honey, and then cooled. The cuttings were then dipped into the honey solution and then placed into the propagation medium. It did work, but the scientific question is how much better would it have worked if the honey was not mixed with boiling water?
- On the other hand, the study by Dunsin et al., (2014) used three types of alternative rooting hormones, pure honey, coconut water and moringa leaf extract. The stem cuttings were treated with the alternative hormones (dipped into them) for 3 minutes and air dried for 5 minutes, then planted.
- Taking a different approach, the method used by Uddinet al., (2020) was that the cut ends of the cuttings were dipped into tap water for 5 minutes, and then taken out and dipped into Aloe vera gel, undiluted honey, cinnamon powder, IBA or IAA, and rolled to create a thin layer, then set aside for 20 minutes to dry, after which they were then planted.
Which Natural Rooting Hormones Work Better Than Honey?
Incidentally, Dunsin et al., (2014) found that coconut water and moringa leaf extract worked better than honey!
- Coconut water contains cytokinins which are plant hormones that helps to stimulate the growth of roots and shoots.
- The leaf extract of the subtropical Moringa tree (Moringa oleifera), also known as the drumstick tree or horseradish tree, contains both auxins (see below) and cytokinins.
Meanwhile, Uddinet al., (2020) found that similar experiments showed that Aloe vera gel worked better than honey.
- The highest survival was 94.7% in IBA treatment followed by cinnamon treatment (92.3%) compared to the lowest survival of 73.3% in the control.
- With the number or roots per cutting, the commercial rooting hormone IBA, which is also found in willow water, produced the most, almost matched by Aloe vera gel, with honey in a respectable third place.
- In terms of root length, the first two leaders swap places, with Aloe vera gel producing the most, with IBA second, and honey third.
It’s worth noting that while honey can be an effective way to help propagate plants from cuttings, there are also other substances that can be used for this purpose, such as rooting hormone powders or gels that contain indole-3-butyric acid (IBA) and naphthaleneacetic acid (NAA).
Although willow water (which contains IBA), coconut water and Aloe vera gel look to be more effective than honey, this natural product still works quite effectively for stimulating root growth in cuttings.
Aloe vera gel is really easy to make at home and can also be used for healing skin conditions and minor burns. For instructions on how to make your own Aloe vera gel, see article – How to Make Aloe Vera Gel from Fresh Aloe Vera Leaves
Before we look further into the properties of honey and how it stimulates root growth in cuttings, it’s helpful to briefly familiarise ourselves with the main plant hormones that produce roots in plant cuttings.
What’s in Commercial Rooting Hormone Products?
Auxins are a class of plant hormones that perform various important functions, such as:
- Regulating growth, principally by stimulating cell elongation in stems
- Cell division and differentiation (production of new cells, and transformation into specific types of plant cells that perform different functions)
- Fruit development
- Inhibition of lateral branching (apical dominance), where the tip bud suppresses the buds below it from shooting and forming side branches, so the energy for growth can be directed vertically upwards.
- Leaf fall (abscission)
- Formation of roots from cuttings
The most important naturally occurring auxin found in plants is the plant hormone indole-3-acetic acid (IAA).
Most commercial rooting hormone products contain two synthetic auxins, indole-3-butyric acid (IBA) and naphthaleneacetic acid (NAA). They have similar structures and functions to the auxin naturally produced by plants, indole-3-acetic acid (IAA), but are more effective in promoting root formation. Studies have shown that IBA is also found to be naturally occurring in plants.
Additionally, commercial rooting hormones usually contain a fungicide to prevent fungi from attacking and rotting the end of cutting inserted into the moist propagating medium.
Honey doesn’t contain any of these compounds but works in a variety of ways to promote root growth in cuttings, which are related to the properties of honey itself, that together prevent it from spoiling.
How Does Honey Help Cuttings Produce Roots?
Dipping the cut end of plant cuttings into honey can help encourage the growth of new roots in the following ways:
- Honey contains natural compounds that can act like rooting hormones, helping to stimulate the growth of new roots on the cutting. While the exact compounds in honey that stimulate root growth in plant cuttings have not been fully identified, several studies have suggested that honey contains a variety of compounds such as enzymes, sugars and vitamins that may play a role in promoting root growth.
- The anti-bacterial properties of honey can help prevent pathogens infecting the cutting by pathogens. For further information, see article – Why Honey Never Spoils.
- The properties of honey help Improve moisture retention. Honey is hygroscopic, meaning it absorbs moisture, which helps retain moisture on the cut end of the cutting, which is important for the development of new roots.
Honey is a supersaturated solution of mainly sugars, with more than 70% sugars and less than 20% water. The sugars make up about 95% of the dry weight of honey. The main sugars are the monosaccharides fructose and glucose which are the most abundant at 70% of total sugars, along with the disaccharide sucrose, (di- meaning two, made of glucose and fructose joined together) which we normally call ‘sugar’. It also contains small quantities of oligosaccharides, these are types of sugars that are comprised of short chains of monosaccharides.
Studies have shown that apart from plant hormones‚ another main factor promoting rooting formation is sucrose (Abo et al., 2018), and that oligosaccharides deposited in the cell wall of plants induce root formation and growth (Mehrabani et al., 2016).
There are several vitamins present in honey, such as Vitamin C and Vitamin B1 (thiamine) which were found to help with the initiation of root in cuttings in many plants (Turetskaya and Polikarpova, 1968). It has been known for a while that vitamins are the promoter of root forming factors in several plant species (Chee, 1995).
It’s worth noting that the specific compounds in honey and their concentration can vary depending on the type of honey, and other factors such as the region and season in which the honey was produced, but any natural honey will work just fine for plant propagation purposes.
- Firth, C.S., Gardener, M., Trask, A., & Manager, N. (2017). Honey as an alternative rooting stimulant for cuttings. <https://www.ctahr.hawaii.edu/uhmg/news/V21-honey-rooting-Firth.pdf>
- Rajan, Rony & Singh, Gurpreet. (2021). A Review on The Use of Organic Rooting Substances for Propagation of Horticulture Crops. Plant Archives. 21. 685-692. 10.51470/Plantarchives.2021.v21.S1.103. <https://www.researchgate.net/publication/349181897_A_Review_On_The_Use_Of_Organic_Rooting_Substances_For_Propagation_Of_Horticulture_Crops>
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- The Science Behind Honey’s Eternal Shelf Life, Smithsonian Magazine, Natasha Geiling, August 22, 2013. <https://www.smithsonianmag.com/science-nature/the-science-behind-honeys-eternal-shelf-life-1218690/>
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