Do we need to wait for floor reset, wait till server save or specific amount of hours?
Short answer: yes. All three are still viable possibilities, although only the first two can result in mature, harvestable sugar cane.
Long answer: I spent the last few days at Liberty Bay plantations and I believe I have the answer. Note that all mentions of days, hours, etc. refer to real time, not Tibia time.
Attempt #1
First attempt was the laziest one as I tried to find an approximate time for regrowth. I cut some sugar cane and left. When I logged back 10 hours later (there was no server save in the meanwhile) the cane had already regrown.
New information: sugar cane grows back in less than 10 hours.
Attempt #2
Second attempt was pretty much the same as the first with one difference - I checked the state of the field a few hours earlier.
New information: sugar cane grows back in less than 7 hours.
Attempt #3
Third attempt started immediately after the previous one, a bit over 5 hours before the server save. I cut some sugar cane; however, this time I kept logging in every hour to check and cut some more. 5 hours later, just before the server save, there was no sign of regrowth.
After the servers were back online, I logged in to see the field completely intact. However; this was one of the special server saves - previously announced and prolonged due to maintenance work. Therefore, I decided to ignore that part for now and consider only the minimal time for regrowth.
New information: sugar cane grows back in more than 5 hours.
Attempt #4
This attempt yielded no new information, as I was unable to log in for a prolonged period of time after harvesting the sugar cane.
No new information.
Attempt #5
This was when things started getting interesting. Yet again, I cut some sugar cane and got to checking back in regular intervals:
On one of those checks, around 4 hours later, I saw this:
While I was offline, someone else went there and mowed the entire field! However, I decided to continue with this attempt - because there was a difference of a few hours, the canes cut by me would surely regrow first, right? So, I threw a single mushroom under the tree in the top-right corner and returned to regular, this time more frequent (every ~20 minutes) checks.
8 hours after the initial cut, after several checks, there was still no change. However, when I logged back in 20 minutes later, the field had fully regrown.
And not just "my" squares, but all the others as well. Furthermore, the time of regrowth completely contradicted previous information (regrowth took 8h to 8h 20m on attempt #5 compared to 5h to 7h from attempts #2 and #3). That could have meant only one thing - sugar cane grows back when the floor reset occurs (although I was surprised to see that the mushroom survived, I guess being few sqms closer to the city somehow saved it).
New information: sugar cane grows back when the floor reset occurs.
Attempt #6
Knowing that regrowth is directly connected to floor resets, this attempt was a mere formality as I decided to check what happens after the server save again. I mowed some canes, then some more right before the server save (a typical one this time) and waited. When I logged back afterwards I wasn't surprised to see the field intact.
New information: sugar cane grows back after the server save.
Attempt #7
This turned out to be the last attempt. Immediately after the servers were back online, I logged in and cut some sugar cane:
When I checked a few hours later, the field was, yet again, completely harvested:
This time, however, it stayed that way much longer than before. 10 hours after the server save (and the initial cut), the field was still empty. Unfortunately, at this point I was too tired and fell asleep soon after. When I woke up and logged back in almost 5 hours later (~15 hours after the initial cut), I was greeted by an unfamiliar sprite:
Someone must have managed to block the floor reset, which allowed me to witness the natural growth. Since it occurred sometime between 10 to 15 hours after the initial cut, I think it is safe to assume that 12 hours is the exact time for the sugar cane to reach the "young" stage.
I remained online for the next 9 hours - until the server save - to see if the cane would naturally reach the mature stage. As I predicted - it didn't:
After the server save the sugar cane was mature again, due to the floor reset.
New information: sugar cane regrows naturally and it takes 12 hours to reach the first stage. Reaching the final stage is impossible as it takes at least 24 hours (possibly more), which cannot happen due to the server save.
So, there it is - while capable of regrowing naturally (which is pretty unlikely to happen since the area isn't frequently visited by players), the sugar cane can be harvested again only after a floor reset.
The last piece of information I have is the approximate time of the floor resets. Since one reset occurred during a 15-minute absence of mine and they are supposedly happening each day at the same time, every 6 hours, I believe the floor reset times are:
- 10:00 CET (server save)
- ~16:30 CET
- ~22:30 CET
- ~04:30 CET