You will enjoy your DIY Greenhouse much more if you keep the number of boring chores to the minimum. Since watering and fertilizing are the most time-consuming tasks you have to do in the greenhouse, it makes sense to try and automate a system to do both.
Domoticz is a Home Automation System that lets you monitor and configure various devices like: Lights, Switches, various sensors/meters like Temperature, Rain, Wind, UV, Electra, Gas, Water and much more. Notifications/Alerts can be sent to any mobile device.
Create in example Greenhouse Watering button.
Click on Timers and set