Potted Plant Protector that was in a recent Make post. This project uses three sensors to monitor the growing conditions of a plant, giving you detailed moisture, light and warmth information. A thorough gardening Arduino system will measure more than just those three types of data, but this is a good starting point. The Make post tells you what parts are needed for this Arduino project, and there's a video that guides you through the project. There are lots of other Arduino gardening projects to be found online, but this one is straightforward, relatively low cost and a quick way to get involved with microcontrollers and the world of plants.
Although this project won't be much of a challenge for the non-beginners in the Humboldt Microcontrollers Group, it might still be an excellent gardening project to start with. To make it more challenging, the advanced people could use the recommended hardware, then write their own code to monitor the growing conditions and display the data. After they have that working, they could download the sketches (Arduino programs) that Make has on their website for the project to compare how Make wrote the project programs and how the Humboldt coders structured the software.
Doing this project would also be a good start toward the aspects of Arduino gardening projects that don't necessarily involve electronic components and the initial programming to capture data. Those aspects include items like determining what moisture percentage is a good target for a given plant and figuring out how to measure the actual moisture, light and temperature levels for calibrating the sensor readings. Once the group has experience with those three sensors, we can figure out which additional sensors, such as soil pH, will give information needed for productive and interesting gardening.
At the May 29 meeting of the Humboldt Microcontroller Group, I'm going to suggest that people in the group who want to do an Arduino gardening project set a date for choosing what they want to do for the first phase of the project (I'll suggest they go with this Potted Plant Protector). By mid or late June, we should be able to have a microcontroller-monitored garden operating and generating information.
Then we'll have to figure out how to use that information to help the plants grow better!!