Gardening Project

So I've been getting really into gardening for the last couple months. It has gotten to the point where I have so many different plants that need to be tended to in different ways, that it is taking up a significant chunk of time.

I don't have more than 2-3 plants that need lighting other than what they get in their permanent location, so watering is the problem. I've been brainstorming to see if I could figure out a way to have the watering controlled by a computer program that I could write. The only problem is the hardware. I have no experience with programmable controllers, and I don't know which ones I should/could use. I have found a few of these complete kits online like this one Cyber-Rain XCI 8-Zone Automated Sprinkler Controller - 01XCISC08 - Smarthome but they're too expensive and I'd also like to do it myself so I can write the scheduling program and also be able to hook it up to a larger number of plants.

I'm sure no one here will have all the answers to this since it's an outlandish question, but any suggestions or will be appreciated!

Jam it back in, in the dark.