Answer: Most landscape trees and shrubs need only about an inch of water per week, even during the hottest months of the year. It is generally recommended that you water deeply once each week; twice each week if weather is extremely hot. Daily watering is excessive and overly moist soils can be depleted of oxygen, something the roots need. Without adequate oxygen, the roots will suffocate. Your arborvitaes sound as though they are suffocating from the excessive applications of water. I'm not sure they can recover, but you can try to help them by immediately stopping your daily watering routine. Wait 3-4 days and dig down into the soil. If it is still moist 2" below the surface, you won't need to water for another 3-4 days; if it is dry, it's time to water.
Q&A Library Searching Tips