If you enjoy gardening, there is a good chance that you are interested in propagating (or cloning) your plants. Who wouldn’t want more plants for free? If you have read articles or watched YouTube videos about propagating, you have probably seen people dipping the ends of their cuttings into a liquid or gel called rooting hormones.
Rooting hormones are plant hormones that stimulate root growth in plants. The class of plant hormones responsible for root growth is auxins. There are commercially available rooting hormones in the form of liquids, gels, and powders.
In this blog post, I will briefly discuss the benefits of propagating your plants. Then I will describe the difference between naturally occurring and commercially available rooting hormones. Finally, I will talk about which rooting hormone (e.g., honey, willow water, aspirin) alternatives actually work!
Why You Should Propagate Plants
Learning how to take cuttings from some of your plants is a great way to generate more of your favorite plants for free. Another benefit of cuttings is that you can produce full-grown plants more quickly than using seeds.
The process of taking cuttings is referred to as plant propagation. In nature, many plants propagate vegetatively (without seeds). This is particularly common for species that live in areas with extreme weather patterns or where wildfires are common.
About Rooting Hormones
Like humans, plants have several different hormones that regulate various aspects of a plant’s development. Plants have five classes of hormones. Auxin is the class of hormones responsible for root growth and development. Auxins are produced in stems, buds, and root tips.
Indole-3-Acetic Acid (IAA)
IAA is a naturally occurring auxin. It is the most abundant plant hormone in the auxin class. IAA breaks down quickly. As a result, it is not commonly used in commercially available rooting hormones.
Indole-3-Butyric Acid (IBA)
IBA is also a naturally occurring rooting hormone. However, there is a much smaller amount of IBA found in plants than IAA. Plants convert IBA to IAA (Fawcett et al., 1960). It is commonly found in commercially available rooting hormones.
Alpha-Naphthalene Acetic Acid (NAA)
NAA is a synthetic (man-made) auxin. It is chemically similar to IAA but is more effective in promoting rooting. It is a common ingredient in many commercially available rooting products and is often combined with IBA.
Commercially Available Rooting Hormones
Although gardeners could mix their own rooting hormones by purchasing ingredients from horticultural suppliers, it is generally easier to purchase ready-to-use products. These products are available as liquids, powders, and gels.
Liquid Rooting Hormones
Liquid rooting hormones are often mixed with alcohol and must be diluted to the appropriate strength. To use liquid rooting hormones, dip cuttings into a more concentrated liquid rooting hormone for 3 to 10 seconds. Cuttings can also be soaked for longer periods of time in a more dilute rooting hormone liquid.
Gel Rooting Hormones
Personally, I prefer using gel rooting hormones because they are not as messy as the other options. It is also convenient which is why it is the most common type of rooting hormone used by home/indoor gardeners. It also covers the cutting more effectively. However, gel rooting hormones are not as versatile (as far as concentration) as rooting hormones available in liquid and powder form.
It is important to remember that you should NOT place cuttings directly into the rooting hormone containers. This can cause contamination and could spread diseases among your plants.
Powder Rooting Hormones
The benefits of powder rooting hormones are that they are easy to use, are available in varying strengths, and a large number of cuttings can be treated quickly. It is important to remember that you must apply powder uniformly to each cutting. Make sure that the base of the cutting is moist so the powder will adhere. You can do this by pressing the cutting onto a damp sponge.
In general, rooting hormone powders are considered to be less effective than liquid rooting hormones of the same concentration. This is because it is more difficult for the plant to uptake the auxin in powdered form. However, rooting hormone powders are less toxic and typically more cost-effective.
Alternatives to Rooting Hormones
Some people prefer using organic products for their gardening. Here is a list of alternative root hormones suggested by various sources.
It is important to note that some rooting hormone alternatives discussed online do not actually contain rooting hormones. Many plant cuttings will grow roots without the addition of rooting hormone because the plant itself contains rooting hormones. This may lead some people to conclude that various homemade products caused the rooting when the plant actually rooted on its own.
Aloe Vera
I am particularly excited about this alternative rooting hormone because it is a gel that will stick to cuttings well. Aloe vera has a high concentration of auxins, so it can be used as a rooting hormone to propagate other plants. If you have a lot of aloe vera in your yard, using it as a rooting hormone could be a good way to save a little money.
To make your own rooting hormone gel with aloe vera, follow these steps:
- First, pick a fresh aloe vera leaf.
- Then cut off the green layer and peel away the gel inside.
- Put the gel in a container and add a little water.
- Finally, blend the substance together and use it for your plant cuttings.
Here is a video that shows you how to make a rooting hormone from aloe vera.
Willow
Willows trees have a lot of auxin (rooting hormone). The auxin is most concentrated at the tips of willow tree branches with little green leaves. You could make your own liquid root hormone solution by producing Willow water. You can do this by following these steps:
- Collect green, actively growing willow stems.
- Cut the stems into 1-inch pieces and mash them.
- Place the mashed stems into the water and bring the water to a boil.
- Remove the mixture from heat and let it cool overnight.
- Remove the willow stems from the mixture and soak your cuttings in the willow water overnight.
Honey
I have seen several sources online that present honey as an organic alternative to commercially available root hormones. Unfortunately, honey does not contain any root hormones. However, honey could still be helpful when propagating plants. Although it will not speed up plant growth, honey has anti-bacterial and anti-fungal properties that will help ensure that your cuttings produce healthy root growth.
Cinnamon
Similar to honey, cinnamon does not contain root hormones. Its natural anti-bacterial and anti-fungal properties allow your cuttings to grow in a healthier environment.
Aspirin
I have also seen many online sources that claim that aspirin can be used as a rooting hormone. Aspirin is a pharmaceutical drug commonly used for pain relief. The main ingredient is acetylsalicylic acid (ASA). This chemical is not a rooting hormone.
There is a natural phytohormone found in plants called Salicylic Acid (SA). This hormone is responsible for plant growth, photosynthesis, and transpiration. SA and ASA are chemically similar, but they will not have the same effect on plants.
In conclusion, aspirin does not contain rooting hormones. It probably has a marginal (if any) effect on root development. However, it does not seem like crushing up aspirin and adding it to water will harm plant cuttings.
Choosing the Right Concentration
The concentration of the liquid rooting hormone is expressed in parts per million (ppm). It is important to note that one ppm is equivalent to one mg/L. The concentration of powdered rooting hormones is expressed as a percentage.
A rooting hormone with a concentration between 500 ppm and 1,500 ppm should be applied to herbaceous (e.g., mint, dill, and grasses) and softwood cuttings (e.g., hydrangeas, azaleas, roses, and cherries). Rooting hormones with a concentration between 1,000 and 3,000 ppm should be applied to woody cuttings (e.g., lavender and thyme). Finally, rooting hormones with a concentration between 5,000 ppm and 10,000 ppm should be applied to hardwood cuttings (e.g., angel’s trumpet).
| Cutting Type | Rooting Hormone Concentration |
| Herbaceous and Softwood Cuttings | 500 ppm – 1,500 ppm |
| Woody Cuttings | 1,000 ppm – 3,000 ppm |
| Hardwood Cuttings | 5,000 ppm – 10,000 ppm |
Rooting hormone powders are typically available in concentrations of 0.1% (1,000 ppm) IBA, 0.3% (3,000 ppm) IBA, and 0.8% (8,000 ppm) IBA. There are some products with higher concentrations for hard-to-root cuttings.
Be careful not to apply rooting hormones with concentrations that are too high. This could damage the plant.
Storing Root Hormones
When selecting a place to put your rooting hormones, it is important to understand how rooting hormones break down over time. There are three main causes of rooting hormones breaking down:
- Microbial destruction
- Enzyme destruction
- Ultraviolet (UV) radiation
To slow down the rate your rooting hormone breaks down, you should store your rooting hormones in sealed containers and place the containers in the refrigerator.
Common Questions
Here are some common questions related to using root hormones to propagate plants.
Will rooting hormone gel wash off in water?
Yes, rooting hormones can wash off in water. Hormones are not soluble in water. Instead of dissolving in water, root hormones will form suspensions in the water and be pulled away from your plant cuttings. This means the rooting hormone will be more effective if the cutting is given enough time to root the hormone.
What causes some plants to root when putting in water but not others?
It is important to remember that every plant is different. Cutting roots, also known as adventitious roots, originate from certain cell types depending on the species. Therefore, you should make sure that you are taking cuttings from the correct location on the plant. For example, stem cuttings are more appropriate for woody shrubs or ornamental plants while leaf cuttings are more appropriate for indoor houseplants.
In addition, it is important to take cuttings in the correct season. The best time to take cuttings of houseplants is from mid-February to the end of August.
As discussed in this blog post, it is also important to make sure that the appropriate hormones (auxins) are present to encourage root growth.
Pathogens can be another issue when propagating plants in water. If a plant does not a robust defense system, it will rot.
Finally, adventitious roots form in young plant tissue.
Does rooting hormone expire?
According to the United States Forest Service Nursery Manual for Native Plants, rooting hormones have a shelf life of 18 to 24 months. Therefore, it may be a good idea to order smaller quantities of root hormone more often. This will ensure that you are using products that are effectively promoting root growth in your cuttings.