What it does:

You've hit this bug, even if you don't know it. Every time you went to a place after the cell was supposed to reset, and wondered "hey why haven't those plants respawned yet?" it's this bug. When you go to Solitude and you see those Nightshade there and then you go grab a cup of coffee and come back and restart the game and they're gone, it's this bug. FloraRespawnFix.esp fixes this bug.

See, since the 1.3 patch there has been a bug in the Skyrim engine that it can't 'remember' that plants, mushrooms, nests, and some salmon have respawned, after you reload a save. So you might go to a place again, see that everything is as it should be (i.e. has respawned), then if you save and reload... poof! it's gone. You have to wait for the cell to reset again. You might not notice it unless you look for it, but I've seen it explained as "oh plants take 30 days to respawn" (they don't, they would normally respawn when the cell they're in resets - like anything else), or that certain plants just don't respawn (they all should), or whatever. Nope, bug. Most players have just gotten used to it.

Well, they don't have to get used to it anymore. This mod can't directly fix Skyrim.exe, but it can alter how these flora and fauna are processed by the executable, such that they are no longer affected by the bug.

http://skyrim.nexusmods.com/mods/31268

The patch for Dawnguard is up. Hearthfire will follow later this weekend. Dragonborn I will probably have done in a few week's time.

Also, I forgot the [RELz] tag in the title. Can a moderator add it please?

Fix is in for Dragonborn. Also patched out some minor conflicts in the Dawnguard and Hearthfire files.

Great mod! Good job fixing an issue otherwise conventionally unfixable!

Is this something you could submit to the Unofficial Skyrim Patch? (and subsequently UDGP, UHFP and UDBP) Love the fix, hate the idea of having another ESP in my load order (several in the case of the DLCs) for an otherwise small world fix. Would love to perhaps see it and its patches merged with USKP, and cut four (five if Convenient Horses) ESPs out of people's load orders.

Also, specifically, great job adding a Convenient Horses patch. Not many would have thought to add that. Mega thumbs up.

That was discussed in a past USKP thread, and Arthmoor decided to leave it out for now, and probably forever. It's a good decision.

Benefits of putting this in USKP:

• Wider adoption.
  
• Fewer mod files.

Points against:

• The method this mod uses to fix flora respawns is, *ahem*, 'controversial', on two counts. One is that it changes many of the TREE references in the game (all of them that give ingredients, to be precise) to point to FLOR base objects instead. The other is that it makes extensive use of the event queue to tell the game when to force the ingredients back on. For the latter personally I don't think it's a problem - many things in the game use that queue and this is just another of them. I did quite a bit of performance testing and aside from temporary increases in save sizes I didn't notice any difference at all. For the former, well I'm not a Skyrim engine expert so I don't know. I haven't noticed any issue from it and no one has had any suspicious complaints yet, but the mod's only been out two weeks.
  
• Because the mod changes TREE references to FLOR ones, all those objects that displayed subtle movements before (thistles, mountain flowers, etc) are now frozen. (Note that this doesn't include trees and anything else that does not give out ingredients - those are left alone.) Personally I don't care and I gladly trade it for respawning flora, but some people will be bothered by it. Put this in the USKP and there will most definitely be flames in the USKP thread. More importantly, the complaints will have a good point.

The points against beat the points for by a mile, IMO.

Huh. Was unaware of the issues contained within the mod based on your chosen methods of solving the problem. Is there literally NO other way to A: respawn the flora while B: having no hit on FPS (as you've worked hard to ensure) and C: still have movement in the flora? I know this sounds a bit silly but I'm actually torn between respawning Flora and that tiny bit of movement. I'm terrible, I know.

Also, technically plants ARE supposed to respawn after 10 or 30 days, that being I assume when a cell is scheduled to reset. http://www.uesp.net/wiki/Skyrim:Respawning. Not sure if that's a thing you already knew (I'm not aware if cell resets are scheduled at 10 or 30 days, or just happen whenever the cell is unloaded or what have you.). Also, by the article, it's quite strange the mechanic they use to respawn cells: For any area to respawn, you must not enter the area during the specified time period. Each time you enter the area, the respawn clock is reset.

That's a terrible way of doing things. Some cells would NEVER respawn in a game, like Whiterun's main area. I pass through Whiterun and its surrounding cells almost daily when I play, so they'd never reset. Couldn't they have made the countdown start from whenever you FIRST enter a 'fresh' or 'reset' cell, and regardless of your entry, it continues to count down. If you're IN the cell when the countdown ends, it adds an hour to the countdown and keeps going. So when you leave, in under an hour, the cell will reset. MUCH higher chance of cells resetting that way.

I wonder if that's a thing that could possibly be scripted? Or is cell resetting hard coded?...

Also, a question to your mod specifically: if I add new flora in a mod, will it also be affected by this bug, and thus require me to perform some kind of similar modification to my added plants as you've done here to the vanilla game? I'm intending to add a lot of respawnable flora to the game world; this is crucial knowledge for a non-crappy mod! :3

That UESP article is correct, that's how Skyrim respawning works.

The whole thing with cells only resetting if you stop visiting them is how things have always worked all the way back to Oblivion at least. So yes, you'd have to stay out of Whiterun for 10 days + 1 hour in order to cause the city cells to reset.

Cell resetting can be called by Papyrus, but that only works on interiors. Exteriors can't be reset that way so you have to wait for the engine to do it. Which is why you sometimes see the advice to "wait 31 days in an isolated cell" being passed around.

Yes, the issue will affect any flora since it's caused by the game engine.

It was the same in Morrowind. You had to stay out of the cell for 72 hours or the cell would never respawn.

Thought so, I just couldn't remember if Morrowind respawned anything or not.

"Dayum shame, Jimmeh." Silly, silly system that leads to popular parts of the game world being notably static. Ah well, nothing to be done except spend time in a diverse range of areas. Anyway, to my previous question: any chance you'll tutorialise your efforts here, bluedanieru? For those of us who intend to add flora to our mods that we'd like to have properly respawn? :3

Does this has something to do with the Bug with mine ores not refilling as they should?

No, ore veins are a different issue that should be fixed in the next USKP update.

I think you are confused what this mod does. Plants do respawn when the cell resets. That's not a problem. The problem is that, after they respawn, you can either harvest them immediately or leave them be. But if you do leave them be, then the next time you restart Skyrim, or even if you just quicksave/quickload, they're going to be gone. The game will have 'forgotten' that they are supposed to have respawned. So basically, once you harvest a plant, it's (almost) permanently harvested. This mod fixes that by starting a timer when you harvest a plant, and when that timer goes off, it deletes the old instance of the harvestable object and puts a fresh one in it's place. That one behaves like an object that has never been harvested (i.e. the game engine won't forget it's supposed to be available to harvest). This is all in the readme.

Now, I say it starts a timer, but it isn't as though every time you harvest something I make a special timer object that's doing the countdown independently or something. Skyrim has a built-in system for tracking timed events like that, it's quite efficient, and that's what I use. Initially I was worried when making this mod that I might overburden this system if it was poorly implemented, but that has not turned out to be the case (and anyway, many many things in the game use this queue already).

Incidentally, this completely bypasses the cell reset system. This mod doesn't care about cell resets. If you harvest something and then just stand there and stare at it long enough, it will respawn right in front of you. (Technical: I can't use the cell reset system because placed objects don't receive OnReset events, and I've found OnCellAttach to be unreliable.)

edit: I hesitated to address your question "Is there literally NO other way" because I don't want to get any hopes up, but, maybe. I didn't think of it until after I had already finished and released this mod (isn't that always how it works). At some point I'll look into it and, if I can make it work, release it as 2.0. (By "at some point" I mean "sometime this year".)
If you add existing FLOR objects (bird's nests, mushrooms, salmon, et al), you should be fine. Users of your mod will either use this mod or not, and the objects will be fixed for them, or not.

However if you want to add TREE objects, they will be affected by this bug. My advice is to make your mod normally, with the TREE objects, and then provide an optional file that puts the fixed FLOR objects in their place. One way of doing that is to make your mod dependent on mine and reuse the new objects my mod creates, but a better way to do it is to copy what I've done to fix the problem, in your mod. You'll have to take a deeper look at what my mod does to figure that out - I won't explain it in detail here. When you do that you'll need to nick the script from my mod which you are free to do.

I can say that plants do not respawn for me after waiting in a house in one region for three in game months also if I wait in another location for three in game months no plants grow back after you have picked them. I never had a plant respawn issue in Morrowind or Oblivion some plants in Skyrim just will not grow back after patch 1.3.

I would like to mention that enemies set at spawn locations in the wilds also do not respawn.

Here is some information I and one other have tested. I have tested rather extensively on this since 1.3 when the bug first surfaced.

Reguarding enemy respawns,

I have reported the respawns now for months since 1.3 and I have started a new character to test this ongoing issue so that this can hopefully be resolved to make the game experience better for all who play Skyrim.

I can say I have a new character for 1.8 I created him the day after 1.8 came out and I can confirm the plant and wilderness respawn points are still bugged with no change in the pattern of the bug.

These locations concerning the enemy respawns from my other thread are still bugged along with some new ones mainly along the roads, that is where I travel to test this out.

1. Southwest of Fort Sungard on a rock a wolf usually spawns.
2. West of Fort Sungard in a crevice a wolf or a bear will spawn in a rocky crevice not far from the road.
3. Southwest of Old Hroldan close to the road or on a dirt road a wolf or a bear will spawn.
4. East of Reachcliff Cave on a road a sabrecat should spawn.
5. Southwest of Windhelm by the bridge close to the city two wolves stand close by the bridge on the road.
6. Northeast of North Brittleshin pass a wolf or a sabrecat should be on a rocky hill.
7. Northwest of Gloomreach by a tree stump by the river there is usually a bear standing there.
8. East of Lunds Hut on a road on the hill there should be one wolf or sabrecat.

Then I checked madmoose7 locations and I can cofirm these locations are bugged as well.

1. The road heading west out of River Wood pretty much all the way to Falkreath.
2. The main road just south of Whiterun, and the road just east of Whiterun heading north in to the pale.
3. The general area outside of markarth, it may well be the entire hold but i haven't checked.
4. The town area of Winterhold, as well as the road going south from the town.
5. The area west of Whiterun, i only noticed that area because the skeleton arm sticking out of the water with the sword won't respawn.
6. The cities Solitude and Whiterun

Now keep in mind these are just a few locations where enemies spawn in the wild it seems if I kill deer and the rabbits and foxes the non hostile wildlife they also do not respawn.

This is after waiting for up to three months at a time in a house: the enemies just never come back.

I want to make a note that enemies at dungeons above and below ground respawn.

Mods don't just read every single thread on the forums. If you'd like a mod to rename your post, your best bet is to hit the report button under your forum avatar on the first post of the topic and simply tell them you forgot to put it in and politely ask them to do it for you. I have hiccups like that every now and then and I've never had a mod disregard such a request.

Maybe this is the kind of Skyrim-wide unfixable bug we should be reporting actively to Bethesda?... Get it balled up into 1.9, or maybe on its own as 1.81?

I have been actively reporting this bug since patch 1.3 surfaced the plant and enemy respawn bugs. Bethesda gave us a partial fix with 1.6 as it fixed enemy respawns at dungeons but the enemy respawns in the wild is still broken they do not respawn and neither does the plant life from Dragonborn to Dawnguard to the base game on mainland Skyrim.

That is a sad, sad thing. Mega props to you for diligently reporting it. Perhaps we can explore other avenues of reporting it? It's a pretty major concern - if you play Skyrim long enough eventually the overworld is going to basically be barren and empty...

FWIW at least some of the wilderness spawns seem to work correctly (I never noticed any of them broken - first I've heard of it). The pack of wolves south of Riverwood respawns fine, and I kill the hell out of deer around Whiterun and they always come back. Are you sure it isn't some mod you've got installed?

Hm. I think I may test base Skyrim w/ the unofficials as soon as I get my hands on Dragonborn in regards to these animal spawns. I do admit I've never seen a shortage of fauna around Whiterun, my general hub of activity and life in the game, though I'll be testing plants as well - see exactly the extent of the damage... Specifically as described in the OP: Harvest, go inside, wait 31 days, go out, observe (expected) respawned plant, save, reload, observe (expected) missing plant...