There was once a potted plant living in an office, but it didn't last long. Though healthy looking when it arrived, it quickly developed yellow leaves which gradually fell off, until there was nothing left but bare sticks. When interviewed about the plant's demise, the office workers all expressed the same confusion, having no idea why it died. Each one had taken care of it and watered it every day.
Perhaps you have heard some version of the sad story of the over-loved house plant. Perhaps it's not so sad, because it illustrates the attraction humans have for a green and growing thing, and the innate urge to take care of it. The tragic part of the story is the office workers’ complete inability to observe and respond to the actual needs of the plant.
Rather than becoming depressed at the thought of these indoor workers, so out of touch with nature that they casually kill a plant, I take heart at the thought of each of them visiting it daily. They feast their eyes on its glossy green leaves, and breathe more deeply in its presence, instinctively sensing the oxygen and positive energy it gives off. If humans have retained this craving for green living things from the time when we were constantly surrounded by them, we’ll be all right: the how’s and why’s of caring for plants can be learned.
Indoor plants aside, understanding proper watering in the garden is a big stumbling block. Many newcomers to the gardening scene seek a road map to follow to achieve success. Myriad rules for watering circulate in online gardening groups from “never water in the evening" to “always water in the evening” to “water at least once a day during hot weather.” Besides being confusing, the problem with these prescriptions is that each garden has different conditions, and needs differ from plant to plant. Rather than simply following rules, it's better to get to know your plants and learn to judge when they need to be irrigated.
It is important to remind those with low confidence in their ability to water properly that this is not rocket science. Nor is there any such thing as a green thumb. The great confusion about watering arises because most of us are not tuned in to what is happening in the natural world. Observe, interact, and be patient. Once you get to know the plants, soil, and weather patterns at your site, you will be better prepared to make watering decisions.
As your knowledge grows, you will probably begin reducing your watering greatly. Most gardeners, like the oblivious office workers, overwater to a great degree. Unsure of what plants need they err on the side of caution. For in-ground gardens this is usually fine because most of the water simply drains away leaving the soil just wet enough to provide for plants needs. If you have the coveted “moist but well drained soil,” there is a large range of irrigation amounts within which plants are happy. The novice gardener waters her tomatoes every day and they thrive, leading her to conclude that they need all that water. I barely water at all once my tomato starts begin to grow and they thrive also, leading me to conclude they need barely any supplemental watering. Both methods lead to success, but mine entails less water and work, and encourages a vast root system, while the beginner's method can be costly in time and water, and promotes a stunted root system. Overwatering means the roots need not grow extensively in search of moisture, creating a needy plant as the season progresses.
A helpful concept in understanding irrigation is effective rainfall. This term can have different meanings depending on the context, but in agriculture it usually refers to the water that remains available for plant use after a rain event. Surface runoff, moisture that evaporates immediately, and water that percolates deeply would not be figured into effective rainfall. The water that does not remain in the root zone has positive effects as it recharges aquifers and streams, and cools surrounding areas, but when watering your garden the goal is to come as close to 100% effective irrigation as possible. To achieve this goal, minimize evaporation by not watering during the heat of the day, and avoiding overhead watering systems. Don't allow bare soil: keep it covered by mulch, and grow plants more closely together. Increase the organic matter content of your soil to improve moisture retention.
Taking these common sense measures should result in less watering and healthier plants. If you find that you still need to water very frequently, investigate the reasons for this rather than assuming that it's just the way things are. The most important step you can take is to become an expert on your site.