There's a surprising lack of games on DSiWare that pretty much require you to play every day. Hello Flowerz seems to be the first, in fact. It does pretty much everything you'd expect from a flower-growing game: you have to take care of flowers by watering them, giving them fresh new soil every day and similar tasks.
Each flower you own can be viewed up close so you can see detailed statistics and whether it's in dire need of anything in particular. The game recommends you to play every day so that you'll notice instantly if they become sick, for example.
Any fully grown plants can be moved to your garden, where you can place them in one of about 10 pre-defined spots. You need 12 of the same type of flower in order to plant them though, as you have to place a whole bed of them, not just one. The garden can also be decorated with other things, like different types of fences or lanterns.
The last thing you can do is arrange flower bouquets in order to send them in to competitions. You can actually check exactly what each competition awards extra points for, though, so winning these usually isn't hard – just meet each of the criteria and it's in the bag.
Like the garden, making bouquets requires you to have flowers in your greenhouse. There is again a number of pre-defined spots you can stick flowers and decorations on, so there's not that wide of a customization range.
Everything you do in these three "sections" of the game unlocks more items for you to use, like different flowers and decorations, and as there is no real goal to the game you'll probably spend most of your time playing trying to make these available.
Everything happens very slowly, so don't expect to spend a lot of time playing the game during any one session – it can take hours for a competition to be judged, for example, so it's best just to do everything and then check back the next day.
The game features a strange mixture of graphics, as everything is 2D except the flowers, which are all 3D. The music is fairly laid-back and relaxing but nothing to get excited about.
If you're looking for a "game" which you can play a few minutes every day that doesn't really require a lot of effort, Hello Flowerz is probably your best bet. The unlockables will definitely entice you to keep coming back, and the whole thing is fairly simple to work with, but those after excitement should steer clear.