I love the gardening skill, mostly because i find it the least relaxing skill in the game. Trying to determine just the right numbers of each plant you can manage in a given amount of time is harder than it seems, since you have to factor in not only the growth times, but also the time it takes to locate a plant that needs water. It's not really possible to grow 2 carrots, 2 broccoli, 2 squash, 4 beets, 6 cabbage, 6 onions, 6 potatoes, 6 bluebells, and 5 cotton (for example) in one 3 minute period (at least at my skill level), even though none of them have more than a 2min55sec grow time. The scanning to find which plant needs water/fertilizer and replanting just takes too much time.

Learning little tricks like separating out the ones you are going to re-plant so you can more reliably click on them has made me a better gardener over time and makes me find this the most strategic skill in the game.