I just planted a row of 10 6-7 foot Arborvitae, and followed the instructions on watering once a week. But with watering them once a week they are turning brown?! I had several knowledgeable people tell me that I should be watering the heck out, and so I have changed over to soaker hose, on for 45 minutes everyday, I live in North Providence, RI. Was the once a week a misprint??
From the Ask this Old House directions - http://www.thisoldhouse.com/toh/how-to/step/0,,20397712_20805078,00.html
-- Fill each dam with water, wait for it to be absorbed, then fill again. When the water soaks in the second time, rake away the dam and add a 2- to 3-inch layer of mulch. Keep it away from the trunks to prevent rot. In the first growing season, water once a week, unless it rains. After that, water if there's no rain for two weeks if you have sandy soil, four weeks if your soil is clayey.--