Rooting hormones help plant cuttings grow new roots. Whether naturally occurring in plants or a store-bought product, find out what works for plant propagation at home.
For an intro to growing your own plants, also see 5 Essential Plant Propagation Methods to Grow Everything.
Rooting Plant Cuttings with Rooting Hormone
When you take a plant cutting to grow a new plant, it’s a race against time.
That piece of plant has been cut off from its life source.
To survive, either the natural rooting hormones (auxins) inherent in the plant are going to kick in or we can assist them.
In general, faster growing plants and young cuttings do fine on their own.
Slow growing plants and woodier cuttings may benefit from the application of rooting hormone. This quickens root growth before rot, disease, or drying out occurs.
I’ve listed plant examples from both groups below.
Why not use rooting hormone for all cuttings?
I see some gardeners do this. My thought is, it’s not necessary, can be wasteful, and in some cases will work against you.
Proper amounts of rooting hormone on the right cutting do just what we hope: stimulate root growth.
Too much and growth is halted.
If the cutting is known to provide enough hormone on its own, let it be.
If it’s slow growing or woody, the added hormone can help.
Natural and Synthetic Rooting Hormones
Rooting hormones exist naturally in plants and we can buy synthetic versions as well.
Natural rooting hormone: auxin
• IAA – Indole-3-acetic acid
Synthetic rooting hormones available in commercial products
• IBA – Indolebuyric acid (synthetic auxin)
• NAA – Naphthalene acetic acid
These are available in gel, powder, and liquid forms. Gel sticks best to plant stems.
Here’s some rooting hormone products at Amazon. When you get one, look for the IBA or NAA to be sure it will work.
What about natural alternatives? I’ve included notes about honey, willow, and more below.
Soil, Soil-less Potting Mix, or Water?
You’ve probably noticed cuttings may be rooted in a variety of media including soil or compost from the garden, a sterile (soil-less) potting mix, sand, or water.
The best choice depends on the species, the cutting and growing conditions.
Generally, I find slow-growing cuttings are more likely to rot if soaked in water. For these ones, I dip the cuttings in rooting hormone and planted in potting mix.
Fast growers may root quite readily in water (sweet potato vine is a good example). I do find, however, that water roots are not as easy to transition to soil.
Overall I prefer using potting mix or vermiculite for cuttings unless I intend to continue growing the plant in water.
Keep in mind that whatever instructions you follow, there are numerous variables that can affect outcome.
The more we follow optimum cuts, timing, temperature, humidity levels, and so on, for each particular species, the better.
As mentioned, with the right cutting at the right time in the right conditions, many plant cuttings will root quite readily either in water or potting mix without the need for rooting hormone.
But, there are some plants that are stubborn.
I gathered this list while reading about rooting hormones: it is not a definitive list but works as a general guide.
Use Rooting Hormone
|Use Rooting Hormone|
|Lots more annuals show moderate benefits including:
Begonia * Fuchsia * Geranium, Pelargoniums * Lantana * Plumbago * Salvia * Vinca major and more.
Applying Rooting Hormone
Read the product label for specific instructions: too much rooting hormone can inhibit growth.
Start with a good cutting (right growth stage and plant section) – your tutorial should give you this info.
- Place a small amount of rooting hormone in a secondary container so you don’t contaminate the source.
- You only need rooting hormone applied to the part of the stem that will be buried.
- Use a dibber to create a hole in the potting mix and insert cutting.
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This is the Wild West of the gardening world. Or, one of many.
There is so much misleading or anecdotal advice about ‘natural’ ingredients believed to trigger root growth, but few if any have any science to back them up.
If you find any peer-reviewed studies that affirm their use for rooting cuttings, please send them along!
Personally, I just use a commercial product as needed since it’s inexpensive and works.
I’m all in favor of experimenting with propagation but not misleading new gardeners with folklore or misinformation.
Here’s a few suggestions I’ve seen mentioned in gardening forums.
They all have other good uses in this world (of course), just not for this purpose:
- Aloe vera gel
- Coconut water
- Honey | Honey is antiseptic and anti-fungal. The theory is that by dipping a cutting in honey, we’re preventing disease. I can’t find any studies to show this. My thought is, if you’re using honey, you can’t apply rooting hormone because the stem is already coated in honey. And, is the threat of disease really so great that you’d rather use the honey than rooting hormone?
- Seaweed extract | There is evidence this can stimulate root growth both in cuttings and transplants. The trouble is finding the right product and application amount. If you want to use a seaweed product, do your homework first. There are a lot of wild claims out there.
- Willow water | This one has been in garden folklore for years.
Willow plants are fast-root growers but there is nothing I can find to show willow water (made by soaking willow branches in water) will create some sort of auxin-rich liquid that could induce root growth in other plants.
For starters, the auxins (if present) would be greatly diluted and I have no idea if it would be in a form that another plant could use. So, do more research if this interests you.
It’s nearly impossible to judge based on anecdotal evidence when there are so many other varying factors.
And that’s rooting hormone 101. Use it wisely and you’ll have lots of free new plants.
~Melissa the Empress of Dirt ♛