Hi – About 3 years ago I planted 8 8-foot black cedars next to a wood fence. They are about 10+ feet now and relatively look healthy. Late spring I noted a few branches on 2 of them where the foilage tips are browning. I now see that on 3 of the cedars. All cedars have new growth and look full. They face south, it is not a windy area. The soil was native clay and when I planted it used clay and triple mix . I fertilize once a year in the spring but do not water frequently. When I do I use a soaker hose. Water does not puddle in these areas as I have landscape fabric around the front where excess water can drain. I do not see signs of little webs, black spot or bugs. Any idea what could cause this? Thanks for your help.
I can help direct you to some really good websites for you to learn more about your black cedar trees. But first, I am hoping that you will be able to confirm that you are growing Thuja occidentalis ‘Nigra’, since the description offered by the American Conifer Society describes them as growing only to about 10 feet after 10 years. American Conifer Society
I think you will find previous posting by the Toronto Master Gardeners as interesting. This site makes the distinction between white and black cedars: torontomastergardeners.ca
The good news is that most of the authorities do not seem to be too worried about a few brown leaves and reassure us that this is perfectly normal. Michigan State University
That being said, the frequent questions on cedar trees to the Toronto Master Gardener website often mention that cedars can suffer from winter burn if the fall has been very dry. They say that you should water your cedar trees well (an hour of soaking once a week is a general guideline) if the fall is dry since the roots of cedars are relatively shallow. These sites give general directions on the care of cedars emphasizing the need to water your cedar trees throughout the fall. An idea is to stick your finger into the soil and the soil should be wet an inch deep. If it is not, then increase the amount of water.
There are few diseases and insects that attack cedars, but you seem to be vigilant. However, may I suggest ongoing observation to ensure that your trees are not infected by any insects, or that your trees have not been infected by anything as serious as root rot. If you continue to be concerned, may I suggest that you get a professional arborist to give you an assessment. An arborist can be found through Landscape Ontario. landscapeontario.com
Enjoy looking after your cedars
1 October, 2021