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On a different post, stormy wrote "Rooting hormone has been shown to not be effective". In my experience this statement is correct. I have had the best cutting success rate when not using hormone and instead using a sterile perlite/peat mix.

My questions are:

  1. Where is the evidence that shows root hormone as ineffective
  2. Is it actually the fungicide in the rooting hormone mix that aids in successful rooting?
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  • Most plants that are propagated through cuttings do not need the extra hormones. Some do. If you are dipping tomato and grape cuttings in rooting hormone you are wasting your money.
    – user10810
    Mar 16, 2017 at 6:32
  • I told my hubby this would incite a great debate! We both had found there were naysayers where rooting hormones were a waste of time, but, we do some with and some without. Only to find in our LITTLE experiments that there were no differences. I've read the chemistry and science and it would make sense for some plants. Some plants esp. the herbaceous ones already HAVE the auxins and fungicides naturally. Here is a rather neutral but informative article; gpnmag.com/article/grower-101-rooting-hormones
    – stormy
    Mar 16, 2017 at 17:45
  • @stormy so is there any scientific evidence that they're not worth using,or is that concept just an opinion or hearsay?
    – Bamboo
    Mar 16, 2017 at 18:27
  • Hearsay would be the best qualifier. We heard this within the last month and are unable to find where we've heard and read this stuff. If I find it I'll pass it along of course. I think there is enough detail that is not being considered where this debate is great and keeping rooting hormone on the back burner is wise. Can't imagine that these chemicals could be harmful to humans except for getting on skin or eaten. Hubby just said we heard this on Public Broadcasting as well like the day after. By putting a stick in the spokes, I've learned lots more...
    – stormy
    Mar 16, 2017 at 22:05
  • After much furious looking for the sources where we had read and learned that rooting hormone was ineffective, I have determined from all the information available that I will still use it. Funny, we threw away expensive rooting hormone when we heard this ineffective label. Learned a few important qualifiers,however in this search as I hope you all have as well...
    – stormy
    Mar 16, 2017 at 22:42

1 Answer 1

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From personal experience, I'd disagree with the statement that rooting hormones are ineffective, but it depends what you're using it for. I prefer the powder formulation to gels or liquids because there seems to be less chance of rot with the powder, and it has a longer shelf life, but essentially, rooting hormone preparations contain a chemical formula that, as far as the cutting is concerned, mimics auxin, the plant hormone largely responsible for root formation.

The use of root hormone preparations is neither essential nor preferable for many plants, but cuttings of many woody plants do seem to root better if they are dipped in hormone rooting powder, and also seem to produce more roots more quickly, reflected in more topgrowth at an earlier stage when compared with those rooted without hormone. In general, I'd use rooting powder for woody, semi ripe cuttings of shrubs, but not on soft cuttings, although there may be exceptions - I usually look up how to propagate a particular plant first from a reliable horticultural source, then decide on the type of cutting and whether hormone rooting powder is useful based on what information I find. I wouldn't use rooting hormone on things like perennials, or leaf cuttings and the like, and I'd say the more important factor in whether a cutting roots readily or not is related to whether it's the right type of cutting and whether it's taken at the right time of year.

Some information here regarding rooting hormones http://www.gardenfundamentals.com/rooting-hormones-what-are-they/ and how to use them here http://www.gardenfundamentals.com/use-rooting-hormone-correctly/

I've so far been unable to find any reference which states that, across the board, rooting hormones have been shown to be ineffective. That doesn't mean there isn't one somewhere, but I can't find it - they are certainly still in use by professional growers.

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  • I take back my comment! Grins!! Another less traveled road that was found to be...interesting but certainly not a reason to not use rooting hormone!!
    – stormy
    Mar 16, 2017 at 22:44
  • I wasn't able to find any field trial evidence for or against using hormone. In the RHS Encyclopedia it stated that hormones "merely quicken" the process but didn't improve strike rate. Recent academic/laboratory evidence seemed mixed ranging from auxin (natural auxin that is, not supplemental) providing a statistical but negligible benefit for root development all the way to auxin been essential.
    – M Pollack
    Mar 17, 2017 at 2:53
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    Ah well, that'd be right - more than one opinion then! I did a small trial myself once - I struck 18 cuttings of 18 different shrubs twice, in mid May one year, weather very warm, used hormone rooting powder on one lot, none on the others. Those with hormone all took and grew on pretty quick - those without didn't all strike and were slower. But might be just the way the cards fell... not exactly a scientific trial!
    – Bamboo
    Mar 17, 2017 at 13:02

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