One of the most important aspects of gardening is making sure that each plant gets the right amount of water. Too little and the plant may die, too much and the roots may rot.
As a general rule, cactus and succulents are some of the only plants that thrive in the very dry conditions, shown in the red zone on the meter. Most houseplants, vegetables, and other garden plants thrive in moist soil, shown in the green area on the meter. Only certain aquatic and bog-like plants thrive from regularly being in wet soil, shown in the blue area on the meter.
With the new baby fruit trees, I try to make sure that they stay consistently moist, watering every 3-4 days. I aim to have the meter read just past the green zone, slightly into the wet blue zone immediately after the watering, and then generally in the high end area of moist. With the majority of my vegetables and other plants, I try to keep the moisture reading in the middle of the green zone.
As you can see in the first picture, the baby plum tree is still moist but due for some additional watering. The baby orange tree and tomato plant in the second and third pictures do not need to be watered at this time since they are plenty wet. They are actually a little more wet than I would like due to a recent irrigation accident (which I will cover at a later date in more detail). The extra watering was along the lines of an unexpected rainstorm, which shouldn’t be too bad in the long run, but in the meantime I am holding off watering these until they actually need the water.
It is important to push the meter deep into the soil to test the moisture where the roots of the plants are, and not test the moisture at the surface of the soil since that is not where the plant gets its water. As you can see in the third picture, the surface of the soil looks dry (more mulch is needed and will be coming soon), but the soil underneath is actually still quite moist.