Cedar Hedge


Hello. I had cedars installed before the winter. They were green but now have turned brown. They feel good to the touch and nothing is falling off. I am just wondering if this is normal or not. I believe they are what is called a Swamp cedar.


Thank you for contacting the Toronto Master gardeners with your inquiry.

Cedars can be a beautiful addition to any landscape however, dieback and yellowing of cedar is a common occurrence and we receive numerous questions regarding this problem.

In most cases, it is not possible to pinpoint one single cause, it is usually the result of a combination of environmental stresses, such as inadequate moisture or sunlight and or soil quality or problems originating at planting. From your photo it is difficult to tell if your cedars are yellowing overall or in specific spots.

Cedars are relatively shallow rooted trees. They are susceptible to drought stress especially on well-drained, sandy soils. During hot summer weather, which was evident during the previous season, root balls can easily dry out during transport or at the site before the trees are transplanted. This prevents new root growth. Watering thoroughly is key for helping cedars take root after planting. A deep thorough watering once or twice a week is better than light, frequent watering. Since cedars retain their needles during the winter it is very important to give all evergreens a thorough soaking before the ground freezes.

Cedars are also susceptible to the drying effects of winter winds. It is advisable that for the first few years after planting cedars be protected from these winds with a burlap screen.

Below is some general information on the subject of yellowing and browning of cedars from one of our earlier posts.  It provides some guidance on watering, pruning and soil amendments that you may find helpful:

  • Cedars thrive on moisture and nutrient-rich soil.  Moisture deficiency after they are planted and before the ground is frozen can lead to browning of the bottom of trees.  If watering isn’t sufficient to encourage strong root growth in the last season or the roots in the root ball were not separated (teased out) before planting, roots may not be able to penetrate into the surrounding soil.  Watering deeply and thoroughly (at least once or twice a week after planting) is key so that the roots can take hold and spread.  This can be done easily by using a soaker hose along the base of the cedars for several hours.  Watering should continue well into the autumn until the ground is frozen to maintain adequate moisture through the winter.  The cold winter winds can desiccate the foliage – once the ground is frozen, the tree cannot take up moisture to replace what is lost from the needles/leaves.
  • What type of soil do you have?  Soil type is very important.  If you have clay soil, roots may have difficulty growing into it, so adding organic matter may be helpful in adjusting the soil structure.  You may also want to check the root ball – if it is still intact or if you find the roots are girdled (growing around each other), you may need to find a way to tease the roots apart to encourage outward growth of new roots.  Make sure the soil around the root ball will allow the roots to penetrate into it so try not to excessively compact the soil during planting.
  • Good quality topsoil and mulch should be used when cedars are planted.  Compost, triple mix or manure are good choices to add along with topsoil when planting – not only do they contain more organic material; they provide more usable nutrients for the roots.  They can easily be added as topdressing on a annual basis to help improve soil structure and allow the soil to retain moisture.  The use of mulch is an excellent way to maintain moisture around the shallow root system of cedars – it also gradually adds nutrients to the soil as it decomposes and will also be beneficial in keeping weeds at bay.
  • Fertilizing the trees after they were planted is a good idea. Although excess fertilizer can cause root burn and prevent the roots from growing, so it is vital to follow the instructions on the container carefully.  It is also important to use a fertilizer with a higher middle (P – Phosphorus) number such as 5-15-5 in order to encourage root growth.
  • Another potenial cause of foliar browning in cedars could be due to root rot especially in clay soils where the drainage is slow. Root rot due to poor drainage could support the pathogen  Armillaria fungus (also known as honey fungus).  Symptoms to look for are the sudden death of the upper parts of the plant during periods of hot dry weather (which we experienced here in Toronto), indicating the failure of the root system’s ability to absorb water. Another tell tale sign is the appearance of white fungal growth at the base of the tree and under the bark of the trunk.

Finally, you should check closely to see if you detect any insects or diseases. Sucking insects such as mites or scale could contribute to the browning you see.

Another one of our earlier posts entitled :  Yellowing Emerald Cedars  is also of interest.