I understand that it's accepted horticultural practice but is there any scientific evidence that deadheading roses actually encourages further flowering?
2 Answers
Depends on the variety of rose - if it's a rambler, they usually have one major flush of flowers all at once in a year and don't flower again till the following year, so deadheading those will not encourage more flowering. With most other types of roses, it does encourage more flowering because it prevents seed cases (rose hips) from forming - the purpose of a flower is to be pollinated and then set seed, and once it's done that, it's not going to bother to flower again the same year.
There are other reasons to deadhead though - done properly, taking a length of stem, subsequent stem and foliage produced will be stronger - without proper deadheading, thin, weak growth can occur.
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Yes, I understand the textbook reasons why roses are deadheaded but I was wondering if there had been controlled trials to confirm that deadheading does in fact encourage further flowering? Jul 27 at 15:14
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2I'm sure there must have been a long time ago or it wouldn't be in the textbooks, most probably by the RHS or Kew, but experiment for yourself if you are unconvinced - deadhead one rose bush and leave another, similar one alone and compare the two over a summer season .– BambooJul 27 at 18:39
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2Also, stop deadheading roses a month before frost to allow those canes to harden for the winter. You don't want to encourage tender new growth late in the season. Jul 27 at 21:36
Very little horticultural practice seems to be based on evidence. I guess it is obvious to anyone that letting roses grow unchecked leaves all the flowers very high. Whether deadheading helps flowering, as far as I can tell, has never been tested scientifically.
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Your statement "Very little horticultural practice seems to be based on evidence." is provably wrong and may imply you don't know how much you don't know. Many of the studies are not on the "free internet", and much of this was studied centuries ago. I did manage to find s3.wp.wsu.edu/uploads/sites/2083/2021/06/… which talks about a Royal Horticultural Study on deadheading etc. Similarly there are videos and papers on not only on the theory but making testable and tested predictions on the fairly immediate effects of deadheading evidencing its efficacy– davidgoOct 21 at 6:54
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Here is an excerpt to one article I found which covers this scientifically - actahort.org/members/showpdf?booknrarnr=1064_23– davidgoOct 21 at 6:56