Just won it, thanks for the tip ! I was trying to do long lines, but it didn't work.
I've been doing them in 1x1 patches so far and could beat them with that method in 44s. I'll try the 2x2 pattern next.
Edit: I tried, but failed at 52s, so I basically lost 8 seconds just by walking in circles... I think, it's much easier to stand between two plants and just turn around after each shower instead of walking in circles.
There's not much I can say about the hoeing challenges.
You need to walk a good path, but try to walk as little as possible (turning 90 ° and hoeing an adjacent tile is way more favorable than crossing a green tile in terms of time-consumption; try to avoid hoeing the green ones if you can). Try to assume a "near-perfect" position, but don't lean in too far into your targeted tile - you might miss it and hit its adjacent tile instead.
If some tiles are arranged in a zig-zag manner, I walk diagonally (a² + b² = c²; you can walk the hypotenuse in less time than the cathetus and the adjacent side.)