Answer: Arborvitae will grow best in an evenly moist yet well drained soil, and they are more tolerant of moister soils than many evergreens would be. They will not survive in standing water, however. In a dry summer such as we have been experiencing, all new shrubs would have required watering to facilitate establishing a good root system and to help them survive. Your goal in watering is to supplement rain to keep the soil evenly moist, but not sopping wet. You would need to dig down into the soil with your finger to see if and when you need to water. It is better to water deeply less often and encourage deeper roots rather than sprinkle a little bit daily. It is a good idea to water deeply, wait a few hours, then dig down and see how effective your watering actually was, it can be surprising. Also, using a layer of several inches of organic mulch over the root zone can help keep the soil moister longer and also keeps down weeds. I hope this answers your question.
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