13 year old cedars. Fertilized twice per year with irrigation. I have looked mites, spiders and do not see any (including webs). Can you help me? Please reach via email, or phone at 416-930-4875. (I have sent two requests because I was unable to attach multiple photos).
Thank you for writing to Toronto Master Gardeners. Browning of the foliage in cedars is a common problem in Toronto. We receive many questions on eastern white cedars (emerald cedar is a common name for the eastern white cedar cultivar Thuja occidentalis ‘Smaragd’) and if you click on this post about “dying and browning emerald cedars“, you will get a detailed answer we provided another inquirer, with advice about the care of these trees, including information on watering requirements.
Cedars are known for their love of water – too little can stress the plant. Conversely, too much can cause root rot. Either too little or too much water can cause foliage browning. Ensure that there is good drainage around your cedars. Is there perhaps a fence that they are planted too closely to behind them? It’s difficult to tell in a photo if the browning is a result of a disease or pest, but the absence of webbing suggests it is not mites. Emerald cedars do naturally drop some needles on the inside of the tree in spring and fall and may need a brushing to remove it. It does appear in your photo there is browning on the outside of the trees, which could indicate a pest.
Toronto’s heat and drought conditions in the summer, coupled with wind and freezing temperatures in the winter make it difficult for cedars. This previous Toronto Master Gardeners post provides a variety of alternatives better suited to our climate.
There is much more information about these cedars on our website. Just type ‘emerald cedar’ into the search box under ‘Find it Here’ on our homepage.