Don't Worry, B-Hoppy..... (with apologies to Bobby McFerrin...)
The daylength and node "requirement" are mentioned in these research papers (title and abstracts below) from a post I saw on the HomebrewTalk.com forum... Shortening daylength is going to be past the solstice, but I have seen flower primordia in plants in my yard before the solstice, and those primordia were initiated and formed well before they were visible to my eye. I am still not clear on it; does the node number requirement include the nodes produced on the bines that are cut off when the first flush is taken off? That would allow the minimum # of nodes to be present on a shorter second flush shoot and allow the hop flowering to start lower down the bine so that more cones will be produced? (that is a question). And my location, on a hill where we get serious radiational cooling most nights, could provide some different temperature condition from many other sites where hops are grown - they mention temperature in those papers too... So confusing - must have a homebrew to clear my head.... (and we must keep the conversation going to try to figure it out!) While my wife may opine differently, I have nothing better to do than spend my days contemplating growth and sensory properties of the glorious hop.
http://www.homebrewtalk.com/f92/inducin ... ps-471404/
Inducing Flowering in Hops
I will start by citing two studies:
H. L. SHEPHARD, J. S. PARKER, P. DARBY and C. C. AINSWORTH. Sexual
development and sex chromosomes in hop. New Phytol. (2000), 148, 397-411
"The switch from vegetative to reproductive development in female hop plants is triggered by shortening daylength (Tournois, 1912; Thomas & Schwabe, 1969). The critical daylength is genotype-dependent, although plants of both sexes must initiate a minimum number of nodes before flowering can be induced (e.g. 30-32 for the variety `Fuggle' ; Thomas & Schwabe, 1969). The influence of daylength on floral induction in male hop plants is less clear. Once these conditions and certain other environmental factors such as temperature are met, the plant switches from the vegetative to the reproductive phase."
Factors Controlling Flowering in the Hop (Humulus lupulus L.)
G. G. THOMAS and W. W. SCHWABE
"In experiments on the effects of daylength on the growth and flowering of the perennial hop it was shown that Humulus lupulus is a short-day plant. The absolute length of the short day is important since very short days (8h) induce dormancy before flowering can occur. Light-break treatment may therefore promote or inhibit flowering according to the associated main photoperiod. A minimum node number must have been differentiated before the hop can be induced to initiate flowers, an effect analogous to the juvenile condition. Minimum leaf number and critical daylength for induction depend on variety. At low temperature, induction is possible with longer photoperiods. Promotion of flowers by growth retardants (B9 and CCC) in unfavourable daylengths, and delay of initiation by gibberellic acid treatment were also observed."