About three months ago I planted 10 nigra arborvitae. I have most heads running along the base of all these trees. I started by watering twice a day for 20 minutes each time for approximately 3 weeks. The trees started to lose their dark green color and turn yellowish with slight browning and the highest point in some drooping. There were also a lot of seedlings growing toward tips of branches. I contacted a landscaper who said to cut back on the water doing 20 minutes every other day which I've done for the past two months. None of the high points are drooping however they haven't turned greener and am still noticing browning. I contacted the nursery where I got the trees and they said I should be watering more approximately an hour a day five times a week for most heads. Now I don't know whether to continue cutting back watering or increase. Been searching a lot but nobody mentions seedlings growing toward tips of branches. Any advice would be greatly appreciated.

From the information provided it is likely the newly transplanted arborvitae became waterlogged and a loss of roots occurred. Yellowing needles can be a sign of either too little or too much soil moisture. Plants should on average receive about 1 inch of water a week once established, depending on soil type. New plantings need to be watered so that the transplanted roots are kept moist, but not waterlogged. While convenient, irrigation systems are hard to manage properly in situations like this. You should consider digging a small hole as deep as the root balls and see if any water collects in the bottom (way too wet). if this is the case, you can dig the hole a little deeper and allow water to collect and physically remove it. this would need to be done for each plant. the hole will also allow soil oxygen back into the soil, something roots require to move both water and nutrients upwards into the plant.