A: It's not how often; it's how much. For example, during winter in St. Louis, we use 2-3 times as much water as we do in the summer.
Q: Why is that?
A: For your plants, summer is winter and vice versa. In our commercial accounts, during summer the air conditioning is going full tilt; and the buildings in most areas are colder than in winter, there is so much humidity that its running down the windows. Conversely during winter, the furnace is going non-stop, the building is warm and there is virtually no humidity. Of course there are exceptions to this rule.
Q: What are the exceptions?
A: Equipment (furnace, AC unit) failure and Climate Zones.
Q: What is a Climate Zone?
A: An area that is different from the majority of the area. For example, plants in a bay window will be the REVERSE of the summer/winter conundrum. Since the bay window is considerably cooler during winter, plants placed here will use much less water in the winter than in the summer.
Q: So how do you determine how much water to use?
A: Whenever possible, the first thing I check for is standing water. If there is, I don’t water til next visit. Then, if possible, I “weigh” the plant. For example, I’ll lift a table plant, or a 6’ Ficus tree; if they are “light”, I’ll soak them; if “heavy”, just a spot. Err on the side of less water. The best way to do this is to obviously have your plants on a schedule. We have 5 day, 10 day and 14 day schedules. For your home plants the best thing to do is to have a day that you check on your plants. If you miss by a day or two, no big deal. Just check before you water. Another good thing to have is an indicator plant.
Q: What is an indicator plant?
A: A plant that uses more water than the others and will droop when its starts to dry. The perfect example is the Spathiphyllum Mauna Loa (White Flag Plant) which will seem to collapse when dry but almost always recover when watered. Splash some on the leaves for quicker recovery.