After two decades of post college gardening experience, I've learned that watering plants is not nearly as simple as people seem to think it is (or should be). I've worked at a couple different plant nurseries in my time. Everyday people would come in with various garden questions. Often these were questions about "What is wrong with my plant." I quickly observed that many people were annoyed, or even offended if it was suggested that maybe the plant just needed water or, in some cases, had been watered too much. We gardeners often tend to view watering as one of those things that is so basic to our hobby or profession that we unconsciously presume ourselves to be experts on the matter. Any suggestion to the contrary is damaging to our egos.
So I made a VERY simple graphic just on determining if your soil is lacking in water. Please note that determining soil water content is not the same as determining if you should water your plants. That's part of the problem with bruised gardener egos. On the surface, watering seems like a very simple subject. But in reality, it is more complicated and our failure to understand that leads to suffering plants and hurt feelings. So do not interpret the simpleness of this graphic as a reflection on the science of watering your plants. The graphic attempts to explain in a simple manner how to determine if your soil is dry enough that your plants MIGHT need water.
Proper garden watering is a subject for multiple blog posts. Maybe even a book? Anyway, here is the graphic. There will be a 100 question exam on it next week.