I have been told by someone whose opinion I highly respect that I would have gotten my point across better without offending Rayrose by posting something more like the following.
Incidentally, when I originally opined that applying triple P as a solution to a fruit trees lack of flowering was a “myth”, I did not realize I was contradicting someone else’s post. I was only responding to the original poster’s statement that she intended to dose the tree with P.
To me, some questions in horticulture are close enough to being settled that an authoritative answer can be given. The question about a plum tree or other plant that refuses to flower is one of the basic questions horticulturists are asked and if you went to any cooperative extension in this country and they reached out to their respective universities for guidance, none would likely suggest that the cause was insufficient phosphorus, especially if symptoms of the deficiency weren’t long apparent in other ways.
If you went to a forum on growing pot or roses and wanted big flowers, however, you’d be blitzed with recommendations to dose those babies up with an extremely high P fertilizer. Hobbyists swear by it.
When I was studying this stuff in school a quarter a century ago, this P theory- the idea that N served the leaves and P serves roots and flowers was debunked by my teachers. I was taught that it is excessive N that can cause overly vigorous vegetative growth that hinders flowering and when combined with ample water can reduce root growth (roots grow to reach water AND N), but that early experiments were done that didn’t differentiate between simply lowering the amount of N and the increasing application of P when concluding that P specifically encouraged flowering. I was taught that the correct balance of N and P encourages both root and fruit.
I believe the myth that high levels of P are required to get big flowers or fruit is perpetuated by folks who are excessively feeding their plants N and follow someone’s advice and substitutes their fertilizer with something extremely high in P but light on the N. When the plants settle down and become focused on sexual reproduction instead of vegetative growth, the P gets the credit when actually it is about the reduction in N.
http://www4.ncsu.edu/~djgofort/Fruit2.htm
Here is an example of how an extension horticulturist might answer the question of why a tree won’t flower. I’m not satisfied with it because I know that fruit trees often don’t flower because of over pruning of the wrong type, which the author of the above article doesn’t mention, but he does address the P issue.
http://www.rose.org/phosphorus-fallacies-too-much-of-a-good-thing/
The above is a well written article about the affect of P on flowering of roses.
Anyhow, the point of all this is that I wish there was a way this forum could present the current understanding of the science on some of the fundamental questions that people come here with instead of a barrage of confusing claims and counter claims based primarily on anecdotal experience. But then it wouldn’t be a forum, it would be a university based cooperative extension. Oh well.
