How To Use Rooting Hormone (3 Ways To Apply It)

Rooting hormone is a good way to increase your chances of success when you propagate a plant from a cutting. However, there are some things to keep in mind when you use rooting hormone.

So, how do you use rooting hormone? To use rooting hormone, take a plant cutting that includes a node (which contains buds). Dip the cutting in rooting hormone (powder or liquid/gel) at the right concentration. Then, put the cutting with rooting hormone in a sterile, soilless growing medium and cover with plastic to retain humidity.

Of course, some plants get more benefit from rooting hormone than others. Rooting hormone can help slow-rooting plants to get a head start and reduce the chance that they will rot before rooting.

In this article, we’ll talk about rooting hormone, including what it is and how to use it. We’ll also talk about what to expect and what to avoid when you use rooting hormone.

Let’s get started.

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What Is Rooting Hormone?

Rooting hormone is a plant growth regulator that encourages root initiation (new roots or adventitious roots) and branching of existing roots. It also promotes denser root growth.

plant roots bamboo — Rooting hormone promotes faster root formation and better root growth in plant cuttings.

Rooting hormones are found naturally in plants. However, they are also available in powder and liquid or gel form (powder is less effective than liquid/gel at the same concentration).

Rooting hormone (auxin) plays many roles in plant development, including development of roots, shoots, and flowers. In the right amount, auxin stimulates root initiation (encouraging the growth of new roots, existing roots, branching roots, and adventitious roots, which form in unusual locations).

Two common auxins include:

NAA (Naphthaleneacetic acid) – a synthetic plant hormone, used in rooting hormone products. It is toxic to plants in high concentrations.
IBA (Indole-3-butyric acid) – a plant hormone that is often dissolved in alcohol for use in rooting (it is also available as a salt for dissolving in water). It is often synthetic, but it can be found naturally in some plants.

NAA napthaleneacetic acid — NAA (napthaleneacetic acid) is an auxin (plant hormone) that promotes root growth.

IBA indole-3 butyric acid — IBA (indole-3-butyric acid) is another auxin (plant hormone) that promotes root growth.

Auxin levels vary throughout the different parts of a plant. The concentration of auxin is part of what tells plants how to develop.

Rooting hormone is often used for plant propagation from cuttings. This propagation method gives a new plant that is identical to the parent plant (for example, this means that the new plant retains variegated foliage and other special characteristics from the parent plant).

A plant cutting gives you a new plant that is identical to the parent plant. For example, it will retain variegated foliage and other special characteristics.

Some plants benefit more from rooting hormone than others. For example, species like dahlia, hydrangea, and mandevilla receive a high benefit from rooting hormone.

blue hydrangea — Hydrangeas receive a large benefit from rooting hormone.

However, species such as coleus, petunia, and sedum receive a low benefit from rooting hormone. You can learn more about which species benefit from rooting hormone here.

There are other methods that may help with rooting (for example, by reducing the risk of fungus in plant cuttings), including:

Cinnamon – there are studies suggesting that cinnamon acts as an antimicrobial to prevent root decay. However, cinnamon itself does not contain auxins (rooting hormones).
Honey – a study at the University of Hawaii showed some promise for honey to promote healthy root growth. However, honey does not contain auxins (rooting hormones). Instead, its antifungal properties likely reduce infections and promote healthier cuttings (which are more likely to root). The effects are more pronounced in some plants than others.
Willow water – willow does contain IBA, but the concentration in willow water might not be high enough to work as a good rooting agent.

How To Use Rooting Hormone

To use rooting hormone, you will need the proper equipment for propagation by plant cuttings. This includes:

A healthy plant (to take the cutting from – there is no sense in propagating a plant with a disease, since the new plant will likely get the disease as well).
A container (large enough to hold the soil and all of the cuttings you want to take).
Rooting medium (such as soilless potting mix – add perlite or vermiculite to retain air in the soil and prevent rot due to fungus).
Plastic bag (this will help to retain moisture in the soil and increase humidity in the air).
Clean pruners (to take the cutting from your plant – use alcohol or bleach to wipe them off and ensure that there are no contaminants from other cuttings you have taken).
Rooting hormone (there are powders and liquids/gels available in various forms, containing NAA or IBA).

A good, sterile, soilless potting mix for plant cuttings will often contain perlite (or perhaps vermiculite).

Once you have the equipment above, it is time to take a cutting. You will need to decide which type of cutting to take from the plant.

The types of plant cuttings include:

Stem (taken from either the tip or a section)
Softwood (taken from new growth, usually in May to July, before the wood hardens)
Semi-hardwood (taken from firm wood on mature growth, usually from July to fall)
Hardwood (taken from shoots that grew in the previous summer, and cut in winter or spring when the plant is dormant)
Leaf (taken from a healthy leaf, this type will need to grow both new roots and stems – the original leaf cutting will disintegrate)
Root (taken from healthy roots when the plant is dormant, this type will produce new stems, and the new stems will produce new roots – the original root cutting will disintegrate)

Not every cutting method will work for every plant. Also, the method you use will affect the chance of successful rooting.

For example, softwood cuttings and cuttings from herbaceous plants are most likely to root. Hardwood cuttings are less likely to root.

When you take a cutting, cut the plant to include a node. A node is an area that contains buds, which can develop into leaves, stems, or flowers.

stem cutting — When you take a plant cutting, be sure it includes a node (an area with buds that can develop into leaves, stems, or flowers).
Image courtesy of user Kumar83 at Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Stem_Cutting.jpg

After making your cut, dip the node in the rooting hormone (powder or liquid/gel). If using powder, keep the cutting dry before and after dipping (this will avoid clumping).

If using an alcohol-based solution, avoid letting it run to the top of the cutting (tip). Otherwise, the leaves will twist.

There are also foliar rooting hormone sprays available.

After you apply rooting hormone to the cutting, it is time to put them in the growing medium. Put as many cuttings as you want in the container and growing medium.

Then, cover with a plastic bag or plastic wrap to retain moisture in the soil and humidity in the air. To save time, you can use a humidity dome for multiple cuttings at once – you can learn more here.

After you take a cutting (unless it is a root or leaf), make sure to cut off the leaves to prevent moisture loss. Transpiration is when plants move water through their tissues (some is lost to the air through evaporation from the leaves).

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Can You Use Too Much Rooting Hormone?

It is possible to use too much rooting hormone on a plant. If you do this, you might see more adventitious roots form (instead of longer roots of other types).

Too much rooting hormone promotes calluses and hinders rooting. So, pay attention to the suggestions on the rooting hormone bottle – concentrations vary, so reach the instructions!

Can You Put Rooting Hormone Directly On Roots?

Once a plant has roots, it is already creating its own rooting hormone. So, it probably doesn’t need any more rooting hormone added to the roots.

root rot — You shouldn’t need to put rooting hormone directly on the roots of plants. If a plant has roots, it is already producing rooting hormone.
Image courtesy of user:
Bjornwireen via:
Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Root_rot_in_cicer
_arietinum_(hydro-grown).jpg

If you took a root cutting from a plant, you are waiting for stems to form (which then form their own roots). You shouldn’t need rooting hormone in that case either.

Can You Mix Rooting Hormone Into The Soil?

You should not mix rooting hormone into garden soil, or plant cuttings with rooting hormone into garden soil. Otherwise, any pathogens present in the soil can infect your new cutting.

repotting plant — Use a sterile, soilless mix (potting mix) for your plant cuttings to reduce the chance of infection.

Instead, use a sterile soilless mix (like potting mix) until the cutting has roots and is established. You can learn how to make soilless homemade potting mix here.

Can You Put Rooting Hormone In Water?

You should only put rooting hormone in water when mixing rooting hormones in water-soluble salt form (to get the right concentration).

However, it is a better idea to buy a rooting hormone liquid or gel in the right concentration. That way, you don’t have to do any mixing.

If you don’t use clean water, any pathogens from water outside (a rain barrel, etc.) can cause the cutting to fail due to rot.

water barrel — Water from a rain barrel may contain pathogens, which can increase the risk of losing a plant cutting before it can grow and establish its roots.

Does Rooting Hormone Make Roots Grow Faster?

Rooting hormone does make roots grow faster. According to Michigan State University, rooting hormone has these effects:

Makes it easier to root plant species that are difficult to root
Speeds up root initiation (formation of new roots)
Improves rooting uniformity
Increases the number of roots
Reduces rooting time

How Long Does It Take For Rooting Hormone To Work?

Rooting hormone varies in the amount of time it takes to work. There are several factors that influence how long rooting hormone needs before you see results.

It depends on:

Plant Species (some plant species root quickly, and others are difficult to root and take a long time to grow roots)
Cutting Type (stem, softwood, semi-hardwood, hardwood, and leaf cuttings will all have different time frames for growth)
Humidity (a plastic bag or wrap will help to retain humidity in the air and moisture in the soil)
Temperature (ideally 65 to 75 degrees Fahrenheit, or 18 to 24 degrees Celsius – a heating mat can help to maintain the right temperature in a chilly house or a greenhouse in cool temperatures)
Amount Of Rooting Hormone (it is important to use the correct concentration of rooting hormone, but also to use the right amount at that concentration)