Oh, ick, waiting for grass to grow back, watering every day...waste of time and energy. For the first year and a half of play I worried about the grass
every day! Then I found the grass regrowth trick! Hooray, no more worries! If you do this exactly as told, it can be the end of your grass problems FOREVER! It works, it's fast, easy and I have never had any problems with it. Do it as often as you like! I did not write this but I copied it into my computer. PS I am not a TT except for this trick. Yes, I was apprehensive at first, but got over that and did it. Here it is:
Grass regrowth trick still works! 
Hi guys, today I'll help you recover your town's grass by time-traveling without losing any of your villagers.
Simple as that. If you are against time-traveling and you consider this method cheating then please do not read any further. FYI I am not a time-traveler in general myself and this is the only occurrence where I time-traveled because my town had transformed from a forest to a desert.
First things first-I didn't discover this method and I do not claim any credit, it has been posted and mentioned in many sites.
Ok, let's start and be sure to follow the following steps carefully.
1. Have beautiful town ordinance active.
Very important if you don't wanna lose your precious flowers and have your town flooded with weeds.
2. Find a villager that wants to leave your town.
The moving villager must ping you and walk toward you to trigger the conversation about leaving. if you find any difficulties finding the mover, talk to your villagers many times, they tend to tell you if someone is thinking about moving.
3. Tell the mover Yes/No.
If you want to keep the villager tell him to stay, if you want him to leave tell him to leave, simple as that. Sometimes they want to stay even if you tell them to leave. If this happens you have to reset and try again. Even if you reset the mover for that day is the same.
4. Time-travel
After you are sure you've done all the above steps save and quit.
Press the home button on your 3ds and go to settings then "today's date".
Change the date to the previous month.
Do not change it 1 month forward as many people claim is the best way, it's not.
If you time-travel 1 month ahead it might spoil your game, such as town aesthetics, colour of grass etc.
So change the month to 1 month before. Exit the settings and load your game.
As soon as you load your game save and quit instantly. Do not talk to anyone or wander around. Nothing has changed yet, this is normal. The mover who you convinced him/her to stay/leave is still in your town.
(This happens because time-travelling any amount of time backwards counts for only 1 in-game day)
After you saved and quit, go to your 3ds setting again and change the date to the current date.. That means 1 month ahead of the current settings.
5. Enjoy.
Load your game and wander around town.
The mover is still there if you had told him to stay or he's gone if you had told him to leave.
Explore your town and witness the regrown shining grass. That's it!
Extra:
After you've done this and you are back to your current time someone else may want to move that day. Even if you've played that day before attempting this method, after you've done this it'll be a completely new day with new fossils, items in shops etc. This is normal. There may be a few weeds and your character will have bedhead.
