Reproducing plants by taking cuttings from existing ones is nothing new. This "cloning" process can occur on its own in nature with zero human intervention, but it has also become a popular tool for both amateur gardening and professional production horticulture. Whether you want to share one of your favorite plants with a friend, expand your garden or increase the consistency of your harvests, cloning is a great option. In our previous tutorial on plant cloning (available here), we discussed what cloning is and the specific steps to take and root a cutting. One of those steps involved the use of a rooting hormone to speed up the formation of new roots from a leaf or stem cutting. While cloning, in and of itself, may not be foreign to most plant lovers, we often find that our customers aren't quite as familiar with the function of rooting hormones in propagation. So, what are rooting hormones and how do they work?

Rooting Hormones: 101

Simply put, a rooting hormone is intended to increase the chances that your fresh cutting will develop roots and become its own independent plant. When you cut a piece of stem or leaf material from a plant and place it in a grow medium, you are essentially asking the cells within the base of that cutting to stop the process of vegetative growth and revert back to producing roots. That's a big ask, so the first step is to dial-in your propagation technique, optimizing humidity and temperature to create the ideal environment for healthy root development. Remember, without those roots, the cutting would have serious difficulty taking up nutrients and growing to maturity.

Photo: Cloned plant 3 weeks after cutting. Stem dipped in rooting hormone gel.

Rooting hormones help ease this transition from vegetative growth to root growth by stimulating cells within the plant through the introduction of chemical compounds.

Chemical Compounds

There are two primary chemical compounds found in the majority of rooting hormones available commercially.

Indole-3-butyric acid (C₁₂H₁₃NO₂ for you chemists), or IBA, is a plant hormone occurring naturally in willow trees and is the most popular ingredient in horticultural rooting products. In its pure form, IBA is a solid crystalline powder. When diluted down, it can also be mixed into liquids and gels.

1-Naphthaleneacetic acid (C₁₀H₇CH₂CO₂H), or NAA, is a completely synthetic plant hormone that is not found in nature. It assists in root development like IBA, but has some potentially negative side effects for the environment. In high doses, it is toxic to plants, animals and people. Therefore, under United States law, products containing NAA must be registered as pesticides with the Environmental Protection Agency (EPA).

Product labeling for any of these items should clearly display the active ingredients and we recommend using them as directed by the manufacturer. Additionally, you'll often be able to find Safety Data Sheets (SDS) online from the companies who make these products, stating safety risks, potential hazards and all active ingredients. We've included links below to SDS sheets for each of the products we discuss.

Now, if you do a quick search online for rooting hormones, you'll probably come across a whole slew of homemade "natural" options. All we can say is to be wary of garden myths. Honey, cinnamon, vinegar, etc., are all touted as DIY rooting hormones, but the chemical compounds called auxins that plants use to stimulate root development are not present in any of these products. Do they help the plant grow roots in some other method like preventing bad fungal growth? Potentially, but they wouldn't technically fall under the category of rooting hormones.

Willow-water, on the other hand, is a natural solution that qualifies as a rooting hormone because willow contains IBA - the same chemical compound used in most commercially available products.

Formulations

If all of the rooting hormones available have essentially the same active ingredients, then what sets them apart from eachother? First, the amount of active ingredients in each product varies slightly, so be sure to look at those labels. Second, the formulation of inactive ingredients can impact both the delivery of rooting hormones to the plants and the physical consistency of the product. Rooting hormones are most commonly available in three different styles: powders, liquids and gels.

Powders

Product: Hormex Rooting Powder

Safety Data Sheet (SDS) 

These are the longest-lasting of the options from a shelf-life perspective and work well when placing your cutting into a firm medium that will hold the powder in place against the stem. Pour some of the powder into a small dish or container. Wet the cut-end of your stem. Roll the wet stem through the powder. Then place into your grow medium.

Liquids

Product: Dip N Grow Rooting Liquid

Safety Data Sheet (SDS)

These are easy to use but run the risk of not staying in contact with the surface of the stem after it's been placed in a grow medium. To use a liquid rooting hormone, simply pour some into a container, dip the cut-end of your stem in it and then place into a grow medium. If you have a hydroponic setup or are using an aeroponic or fogponic system such as the TurboKloner, you can mix this liquid into your reservoir, providing a constant application of hormone to the area in which you wish roots to form.

Gels

Product: Clonex Rooting Gel

Safety Data Sheet (SDS)

It doesn't get much simpler than cloning gel. Just as with powder, it works best when placing your cutting into a firm medium that will hold the gel in place against the stem. The gel does a better job, though, of staying in full contact with the stem than a liquid.

Our Recommendation

When it comes to rooting hormones, we have yet to see one product with a "secret sauce" that everyone else is yet to discover. In general, they contain the same active ingredients in similar proportions. The delivery method is what makes them unique and should be taken into account when making your selection. As long as IBA is present in the solution, expect to see similar results. When in doubt, call (913-397-0594) or email us ([email protected]) and we're happy to help you find the product that's best for your grow.