No. 4: How Much is Enough
Be observant. Your plants will pretty much tell you what they need.
Give trees and shrubs—especially newly-planted ones—direct watering every 7 to 10 days; don’t rely on sprinklers or irrigation systems in the heat of summer to deliver the necessary moisture as roots will be both wide and very deep. For perennials and annuals, you can water by hand, or with an automatic irrigation system with moisture sensor, or a soaker hose.
If watering with a hose or watering can, start slowly and allow the top inches of soil to absorb water then gradually add more water for a thorough soak. This can mean watering two or more times in a session.
If employing an irrigation system, either depend on the moisture sensor or use the can test to help figure out how long you’ll need to run the system to get the adequate amount of water. (The “can test” is simply placing an empty can in the watering zone, turning on the irrigation system and seeing how long it takes to get one inch of water into the vessel. That will give you great info on how long to run your system.)
If using a soaker hose, use a moisture probe or just your finger to see how long it takes for the system to get soil thoroughly moist 1 -2 inches below the surface and then set timer accordingly.
How far out from the base of the plant should you thoroughly water? The roots are probably as wide as the plant and may be a foot or two deep.
One great way to get this right, especially with newly planted specimens, is to build a soil berm from compost (apply 3 inches of compost around the plant and then pull it back from the base of the plant to the outer edge of the plant’s canopy to form a circular wall) and fill that space with water twice or even three times until the water is absorbed.