I made a self-watering flower pot with an arduino, a moisture sensor and a small pump once. Worked like a charm. Well, until I forgot to put water in the reservoir, that is. I suppose I could hook it up to water mains, but I couldn't be bothered.

The plants we have at home are 'trained' properly so they can survive with an intermittent splash of water every now and then. At the office we have hydroculture and a gardener that takes care of them.