Q. I read your piece in the LV Review/Journal regarding the subject.  You recommended not increasing the length of watering time when it get hotter, but increasing the number of days one waters. How much time or number of days is adequate?  I have:  Heavenly Bamboo, Gold Spot Euonymus and Golden Euonymus, Box leaf Euonymus, Pinkie Hawthorne, Med Fan Palms, Variegated Mock Orange, Pineapple Guava and more.  I live in a newer neighborhood where our plants are 1-3 years old and the landscaper put our drips on for 10 minutes twice per day when they were installed.  I can understand this when the roots are shallow, but 3 years later I’d think that is too much. Presently, I have two drips systems and have both on for 15 minutes 3 times per week for all plants. A. These are very difficult questions to answer for a specific person because they are site-specific. The difficulty in giving you precise watering information is because of the soil at your site and how your irrigation system was designed. Whenever you have a site that has a number of different types of plants growing in the same location, it’s difficult to answer with any kind of precision. I will try to answer your email as specifically as I can and in general terms. Distribution of water. When we water plants we fill the soil with water that surrounds their roots. The water should be distributed beneath the plant so that the area receiving water is about half of the area under the canopy of the plant. In very general terms, this means spacing drip emitters usually about 18 inches apart from most soils. If irrigation basins surround the plant, the basins must be level even if the soil is not. In soils with a lot of clay we can space emitters much farther apart. In soils that are mostly sand, the emitters must be placed closer together. So we strike a happy medium at about 18 inches apart. Make sure you have enough emitters for plants and make sure they are spaced far enough apart to spread the water applied to the soil more evenly and over a greater distance. Emitters can be located from six to 18 inches from the base of the plant. So for instance a 1 gallon plant would only require one drip emitter about 6 inches away. A 5 gallon plant would require 2 to 3 emitters about 12 inches away. A 15 gallon plant might require 3 to 4 emitters about 12 to 18 inches away. A 24 inch box plant might require 6 to 8 emitters scattered 18 inches apart under the canopy.  Basically we want the water delivered to the plant so that it spreads as evenly as possible over the roots. How many minutes. As I said above, when we water plants we fill the soil with water that surrounds their roots. The number of minutes to run the cycle depends on how deep the roots are and how fast the soil fills with water from the emitters.  We generally figure that lawn roots are watered 10 to 12 inches deep, most annual vegetables and annual flowers are watered to the same depth as a lawn at 10 to 12 inches deep. There are exceptions in the vegetables such as onions, garlic at 6 inches deep. Small shrubs we figure have roots 12 to 18 inches deep and need water delivered to this depth. Big trees and shrubs we figure have roots 18 to 24 inches deep and need water delivered this deep.  Depth of root system of different plants and depth of watering based upon their size We set the minutes on our irrigation clock after we find out how many minutes it takes to get water to these depths. The only real way to determine the number of minutes needed is to run the irrigation for a certain number of minutes and “see” how deep the water goes. We can “see” how deep the water goes after a certain number of minutes using a little trick. This is the trick: “Sharp objects pushed into wet soil are pushed in much easier than the same sharp object pushed into dry soil.” So we run the cycle for, let’s say, 10 minutes. We wait another 10 minutes so the water finishes draining and push along sharp object into the soil next to the drip emitters in several locations. By “feeling” the resistance it takes to push these objects into the soil gives us the approximate depth that 10 minutes of water delivered. If the irrigation is not deep enough, we increase the number of minutes until we get the depth we want.  This sounds complicated but once we do this we seldom need to change the number of minutes on the irrigation clock. This is because irrigating plants is like filling the gas tank on a car. If we drive the car until half of the gas tank is empty, we will fill the gas tank to the brim. I am willing to bet that if we fill that gas tank at the same pump each time, it will take the same number of minutes to fill half the gas tank every single time. This is the reason we can leave the minutes unchanged when we irrigate provided we use half of the water that we put into the soil each and every time before the next irrigation. How often? This refers to the number of days we irrigate each week or every two weeks or every month. The unit of measurement (week, two weeks, monthly) depends on the irrigation clock. For simplicity let’s use weekly. I know this looks complicated. This is the general water requirement for plants on a daily basis for different months of the year in Las Vegas Nevada. We know that plants use more water in the summer than they do the winter. Remember we are filling a gas tank so we