This is a correction of post #56 of this thread. I edited that post with a correction statement and said I would re-post, so here it is.
Reason for edit: I had the daylength thing wrong - I based the long-day comments on the "Grower Notes 2016.pdf" (Great Lakes Hops) document B-Hoppy had shared (pg 22 - "It takes between four to six weeks for a cut hop to recover and regrow the 12 internode leaf sets needed to accept the long day length signal that initiates burr formation." I think this is incorrect. Hops are short day plants and are induced to flower in SHORT days before or after the longest days of mid-summer; this is from several scientific publications listed in the original post of the "Inducing Hops to Flower" thread (
https://www.homebrewtalk.com/showthread.php?t=471404). There you will also read that it is not just 10-12 nodes, but the node # required for floral induction is variety-dependent. And, for completeness, if the days are too short the plants will begin to go into their dormant phase - although this is not a problem with field grown hops in our normal seasons. I have seen on my own hops the appearance of visible flower buds before the solstice - and since visible buds mean floral induction quite some time before, it is clear that the hops were induced to flower in shorter days earlier in the spring. Let me also point out that no one is putting hard numbers on precise day lengths, photoperiod, (actually night lengths does the magic...) or node number since this does seem to vary by variety. And I am not sure (since people don't make it clear) if the node number requirement includes the formed nodes (primordia) in the compressed shoot apex, or visible nodes with expanding; it is probably this visible nodes since field researchers can't be counting the hidden primordial nodes.
Simple fact is we often see the first unopened flower buds around mid-June to the solstice (in the northern latitudes; earlier if growth starts earlier in the southlands), but they were induced to flower and started making those buds much earlier in the spring. That "asparagus" looking shoot is highly compressed and already has many leaf and bud primordia buried down in the apical region invisible when just looking at the outside. Here is a link of a section of a shoot apex (this is not hops, but illustrates the point of compressed shoots and primordia):
http://www.vcbio.science.ru.nl/publi...ipOverview.jpg
So if you are cutting back to control the size of the mature plant, or to try to set a harvest date, you need to have "sufficient" regrowth before approaching the longest days, else flower induction may be delayed until post-solstice shorter days and make maturation quite late or reduce the crop. I can say that I have cut back Chinook, Cascade, Nugget, Willamette at my location in Massachusetts on May5 (2015) and got "normal" growth and flowering and crop (picked 3rd week of August), but smaller plants than un-cut plants in previous years.
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Edited post, hopefully correct...
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This discussion has been great. That literature b-hoppy shared has helped me understand a lot about hops growing. I hadn't found a complete discussion of this in any one place. For me, it is important to understand WHY we do something since that informs us of how it should be done in other conditions. I'm going to summarize some takeaways I've gained from this discussion and that literature and maybe people can edit the summary so we get it close to right and as simple as possible.
First of all and very important, hops culture will depend on your location (latitude, climate) and the vigor of the variety you are dealing with. Hops will tend to produce the most crop on the upper part of the growth. A hop that can start growing early in the season (early spring, mild climate, long days) will produce a bine that will get very large, possibly overgrowing the available trellis and drooping over and getting thick and tangled, and this will be hard to harvest and the thick, tangled growth may encourage disease. A very vigorous variety in excellent soil conditions will have more tendency in this direction than a less vigorous variety. You will need to observe how your hops grow in your soils and location and adjust any cutting back to fit your situation.
The spring and early season management can be determined by backing up from the end of season. You want the cones mature and dry before the season gets too advanced. In the Northeast the season rapidly gets cool and damp toward the end of August. I like to get my cones mature and picked around mid-August. Other locations will be different. But from experience, start with that general harvest date and back up to determine when to do any final cut-back (if it is needed at all!).
You want your trellis to be about 20' high and you want the mature hops to fill the trellis at the end of season. Hops will tend to overgrow anything smaller and this is why most commercial trellis systems are about this height.
You want the bines to have 12+ nodes by the solstice*; a minimum number of nodes (variety dependent!) is needed to allow floral induction during the short days before or after the solstice. Hops are sensitive to photoperiod - day, or night length. The bines will be florally induced in the short days before/after the long days of mid-summer. It takes about 6-8 weeks for a cut back bine to reach sufficient size (node#) and be sensitive to the short days (long nights!). (? variety, vigor, microenvironment dependent). The bines will continue to elongate and will begin producing flowers and sidearms at the leaf nodes for about another month and will fill out the trellis without overgrowing (? based on vigor of plants).
* This is from post #51 of this thread (
https://www.homebrewtalk.com/showthread.php?t=232819&page=6); Also see references in the original post of this thread:
https://www.homebrewtalk.com/showthread.php?t=471404
The flowers take about a month from burr stage until cones are mature and ready to pick (variable, by variety and environment). Since the flowering occurs over some time (earlier on lower nodes/side arms, later in the upper regions) you want to use a date that is the average for the bulk of the crop for that variety in your location.
People report getting 2 harvests in places where the growing season is sufficiently long.
A streamline summary for the Northern US:
1) Cut back (if needed, last time) 6-8 weeks before the solstice so that you have sufficient nodes produced before the solstice. Yes, you can cut back to the ground (if needed). They will grow. Established hops are very difficult to kill.
2) Hops will continue to grow, make sidearms, and flower (burr stage) for about a month after the solstice.
3) The burrs will mature to cones and ripen in about a month after burr stage.
4) Adjust this for your location and climate, variety and vigor.
And don't neglect to prune the rhizomes of the hops in in the second year and beyond. The rhizomes are not the roots. If you study the shoots from the hop crown you see that the ones at the center grow mostly upright, while the ones at the periphery will tend to be almost horizontal. There are even ones you don't see that ARE horizontal and at/below the surface; these are the developing rhizomes. The rhizomes are a means of the hop plant to spread itself and this serves no purpose to producing a hops crop. Study the hops plant and learn it's ways. The rhizomes start in early to mid season of established plants. If you have light, organic soil it is easy to find them in mid/late summer - white, succulent, horizontally growing "shoots" that are in the upper few inches of the soil, pushing up an emergent shoot at the outer end. The roots are tan and will have fibrous roots; don't prune these. The rhizomes will send up shoots at their tips, and eventually the white succulent young rhizome shoot becomes tougher and will develop fibrous roots, and this would establish a competing and choking new crown. The rhizomes can be removed at any time, but it may enough to do it every spring in established plants. You are not hurting your plant to cut it back (as needed) and remove rhizomes, or even root prune beyond a 2 foot radius of the crown. All of this cutting and pruning keeps the plant vigorous and able to produce the crop you wish to produce.
Hope this helps!
Cheers!
This seems to say that ripping up the surface rhizomes and cutting back is going to be good, not bad, and that one shouldn't worry about physical damage to our dear plants. Ripping up all those easily accessed surface rhizomes will certainly help cut down on the explosion of wild growth spreading from the base. And help control spreading. 
Planted the last 5 Galenas on Monday and now all the holes are filled and rows are complete. As I was walking around the hop yard last night, I had a bizarre thought...it would be so easy to double the size of the yard by just taking 1 rhizome from each plant....scary thought. 
It's taken me 3 years to get where I am already, I probably have enough work for one guy to manage, with my son's occasional help. 
