Rooting hormones help plant cuttings grow new roots but commercial ones are not always wise to use. Find out when (of if) to use them when propagating plant cuttings through the seasons.
For an introduction 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, most importantly, might do more harm than good.
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 seem to work best.
Here are some rooting hormone products at Amazon. When you get one, look for the IBA or NAA to be sure it will work.
Rooting Hormone Powder | Amazon
Rooting Hormone Gel | Amazon
What about natural alternatives? I’ve included notes about honey, willow, and more below.
Should I Start Cuttings in 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, I dip the cuttings in rooting hormone and plant 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.
Watch the Video
This video shows how I prepare hardwood cuttings for rooting. There are dozens of plants you can propagate this way. These ones are good candidates for rooting hormone.
Rooting Hormone Plant Lists
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 starter guide.
Perennials
1Use Rooting Hormone
- Baptisia
- Euphorbia
- Gypsophila
- Heuchera
- Hydrangea | See tutorial here
- Iberis
- Lithodora diffusa
- Poinsettia
2Moderately Beneficial
- Artemesia
- Buddleia
- Campanula
- Caryopteris
- Ceratostigma
- Coreopsis
- Delosperma
- Lavender
- Leucanthemum
- Lobelia
- Malva
- Penstemon
- Phlox paniculata
- Phlox subulata
Annuals
3Use Rooting Hormone
- Bougainvilla
- Brachycome
- Bracteantha
- Calibrachoa
- Cineraria
- Crossandra
- Dahlia
- Dracaena
- Heliotrope
- Hibiscus
- Lobelia
- Mandevilla
- Mimulus
- Osteospermum
- Phlox drummondii
- Scaevola
- Thunbergia
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. Then gently fill in any gaps.
Rooting Hormone | Amazon
Recommended Resources
These are some of my favorite books on plant propagation. They have photo tutorials for growing plants from a variety of methods. Once you know the basics, it’s super fun and addictive.
Grow Your Own Garden by Carol Klein was the first one I bought and still the one I refer to most.
AHS Plant Propagation
Amazon
Grow Your Own Garden
Amazon or here: Amazon.co.uk
Also:
- Plant Parenting by Leslie Halleck
- Plant Propagator’s Bible by Miranda Smith
Natural Alternatives to Synthetic Rooting Hormone
Do They Work?
NEW! Click play to listen: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:
1 Aloe vera gel
2 Aspirin
3 Cinnamon
4 Coconut water
5 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 which will actually encourage root growth?
6 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.
7 Willow water
This one has been in garden folklore for years probably because auxins are present in willow.
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. I realize it’s recommended a lot but my point is, I can’t find research to support it. And, the advice is quite vague: how much auxin could there be and how much water should you use?
Certainly do your own research if this topic 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 ♛
