Question
We have two 7 yr old Dawn Redwoods.  One is robust, green and healthy while the other has minimal leaves and a brownish color.  The problem may be due to a continuous problem with nutsedge weeds around the base of the tree which starts in the summer and grows profusely in moist, wet conditions. We used Roundup to treat this perennial weed each year, as pulling it only spreads the runners, creating more weeds.  Is there anyway to save this tree?  Thanks for your help.

Answer
The grass is taking the moisture that the tree will need . I would mulch around the tree with not more than 3 inches deep of organic mulch not piled up on the trunk. Place about three feet around the tree. Spray the area with the Roundup keeping the herbicide off the trunk. Then put down the mulch and you will need to re-spray when you see any new growth of the nutsedge. This plant is difficult to kill and will take several applications to rid the area of the sedge.