Perhaps the most common question I am asked when selling a new plant is, “how much water should I give it?” A quick and easy answer is 2 or 3 times a week. A better answer is, put your hand in the soil and feel if it is wet or dry. Today, it seems, most people want quick, easy, tidy answers that fit in a box. That’s not gardening! “Gardening is not a spectator sport,” as my friend and colleague Eileen Ferrer has said many times before.
I find it best, when describing water tactics, to give analogies. Take for instance, a sponge in a sink. If you keep the sponge wet all the time, bacteria can develop. Conversely, if you go away for a week on vacation, you can break the sponge in half as it will have dried out. You want the consistency of the soil to be like a sponge after it has been wrung out. Moist with the ability to dry out and get ready to receive more water. “Roots are critical to a plant’s life. They are the primary source for water, food and the intake of oxygen. The roots of the plant take up water but they also need air to breathe. Overwatering, in simple terms, drowns your plant. Oxygen fills the space between the particles of soil. Soil that is constantly wet won’t have enough air pockets and plants will not be able to breathe by taking up oxygen with their roots” (valleycresttakeson.com). Couple this with planting your plant too deeply, another common mistake. Here’s another analogy for you. If you are standing in a pool of water and your nose is 1 inch above the water line, you can still breath. However, add 1.5 inches of water and you will drown. The same holds true for plants. Make sure the shoulders of the plant, the root flare or soil mass when you pull your plant out of its container, is slightly higher than the soil line.
Moving on, let’s talk about sprinkler systems for a moment. Again, many customers want to simplify watering as much as possible. When you install a sprinkler system, it is important to have separate zones for your lawn and for your plant material. Why, because the root system of your lawn may only be a few inches deep, whereas your plants may have root systems that are several feet deep. Proper watering habits promote deep root growth and this is critical for a plants growth and performance. Simply running your lawn sprinklers longer to accommodate your plants will most likely result in your lawn having fungal issues or other stressful outcomes. Important to also note that you have to monitor and, most likely, adjust your sprinkler clock every few weeks based on the weather. Just because you have exercised your wallet and installed an irrigation system does not mean your responsibilities end there. Cooler months will not require as many minutes per zone while warmer months will need more time on the clock, adjusting for evaporation and extreme heat. Additionally, rain sensors are well worth the money, preventing the silliness of seeing sprinklers running in the middle of a rain storm.
There is no easy answer on how long it takes to water a particular tree or shrub. Most home hose spigots, left wide open, can have about 5 gallons of water come out in 1 minute. To test yours, open your spigot and see if you can fill a 5-gallon bucket in 60 seconds. Putting a water reducer, such as a nozzle, at the end of the hose will lessen the output slightly. When you water your annuals, perennials, shrubs and larger trees, think about the 5-gallon pail visual. If your mulch is lifting and floating away, you’re probably watering too much. Contrarily, 10-20 seconds on a larger caliper tree is not nearly enough.
Finally, if you really want to understand water mechanics and fully invest in your new plantings, consider a tensiometer. “A tensiometer measures soil moisture. It is an instrument designed to measure the tension or suction that plants’ roots must exert to extract water from the soil. This tension is a direct measure of the availability of water to a plant” (agriculture.vic.gov.au). They, quite simply, provide a suitable method to aid in your irrigation decisions should you need extra help. Realistically and pragmatically, you can start with checking your plants 2 or 3 times a week, but putting your hand into the soil is always my best advice.