Butlers generally have Cooking and Handiness maxed, and I don't know of any way to make a butler learn Gardening. Also, I don't think any Sim will autonomously tend/weed/harvest the plants in the garden (I'm guessing Green-Thumbs will autonomously go talk to plants if their social is low, but don't think they'd tend them). Maids never tend the garden.
In addition to Metro's two options, here's a third one:
3) Make sure all your plants are in range for the sprinkler. Harvest them as wanted, and weed only when you have time to do so.