Originally Posted by Dazarath
Here's a quick guide on how to get started with the Zen Garden.
If you don't have enough money to buy 3 marigolds, the red present, plus some fertilizer/bug spray, just play adventure or minigames until you save up enough.
Go buy the marigolds and the red present (ignore the bronze/silver/gold ones for now). Water the sprouts with the watering can and then wait until the droplet icon shows up again. Do this a few times until it shows one of the following icons on the plant: fertilizer, bug spray, music box. At this point, the plants will grow a little bit, and you'll have to wait awhile until you can water them again. I'm not sure exactly how long, but it might be an hour+. Repeat this process until they drop diamonds, at which point they are fully matured.
Each day starting at midnight, you can return to Dave's shop and buy more plants. If you don't have enough money, sell some of your matured plants. Right now, the goal is to get a garden full of plants (any type), so only sell as many as you need to. (I would probably recommend starting the next step once you have 1/2-3/4 of your garden filled with plants.)
You may have noticed that watering matured plants causes them to glow and drop money. Get Stinky the Snail from Dave's shop if you don't have him yet, and hopefully you have some chocolate saved up from playing regular modes. Water all of your plants and give them fertilizer/bug spray/music so that they're all glowing. Use a chocolate on Stinky. I think each chocolate should earn you 12k+ in money if you log out of the game. I've heard that you earn more if you leave the game running, but I haven't done extensive testing.
Remember, even as you're farming with chocolates, you can still sell 4 plants each day to buy the new ones from Dave's shop for some extra money (and to get closer to the Zen Garden achievement).
I hope this helps.
I never had a chance to respond to this but wanted to make sure that I posted to thank you after earning my first $10k (so far) today with this help. I had built up some plants and was just kind of getting along, selling them to buy the night garden and the aquarium, but never really getting into the realm of making good money from the garden. Well I finally started focusing on quantity and using the snail and it's amazing how much it pays off. The only thing that I think you were off about was that you don't get chocolates until after you actually buy the snail (at least I didn't, and when I bought the snail they started coming fairly often).
Anyway, thanks a ton for writing this all out. I'll finally get to buy some (likely all) of the mini-game packs now with a minor amount of work.