Question
I have planted a row of  5-6 ft American arbovitaes two weeks ago facing west.  They appear to be healthy at first.  However, this week some of the leaves are turning yellow and drying out.  The stems and branches appear to dry as well. They have adequate water.I have watered it 3x-4x weekly. I also added mulch to cover them.  I also planted some colorado spruce around 36 inches tall.  They are turning yellowish with sap coming out from the stem and also shedding needles.

Answer
Paul,

What are the soil conditions like? Are the Arbs planted in clay soil? Clay soil retains water more readily than any other type of soil, so it is very possible that you have been overwatering them.

I would recommend cutting back on the water to 2 times a week if needed. Fertilize them with a balanced fertilizer and make sure that any burlap that was around the root ball has been cut away to give roots easier access to the surrounding soil.

Good luck,
Ed Gulliksen