Emerald Cedars in distress

(Question)

Last year I planted three 6 foot Emerald Cedars.  Two of them seemed to take just fine, but one did not.  It was replaced just a few weeks after purchase.  They seemed to be doing well going into and out of the winter, but now all 3 appear to be in distress.  They are browning very quickly, and starting to ‘sag’ at the top instead of pointing straight up like they did last year.  I’m concerned that since it’s all 3, the problem is either a pest or soil issue.  I’ve included a picture of one of the trunks which I noticed did not look right.  Wondering if you can help me determine what the issue might be, and if there is anything I can do to bring these plants back to life?

(Answer)

It is disappointing that your Emerald cedars are not thriving.  We have had questions from many gardeners on this subject recently.

Your cedar’s trunk may have split due to the cold winter – this is one of the most common reasons for what are called “frost cracks”.  It could also be caused by “sun scald”, which is where the winter sun shines on a frozen tree trunk and thaws out the cells just under the surface of the bark – this is typical in freeze/thaw cycles during winter.

Here in Ontario, winter 2015 was quite severe with long periods of frigid temperatures but was also quite sunny, so one or both of the above scenarios may have taken place.

There is not much you can do about cracks in the trunk, but they often don’t pose a significant threat to the tree’s overall health.  Water and feed your cedars well over the coming weeks and into the summer and you should see some improvement.  Keep all mulch away from direct contact with the bark of the trees as you don’t want to encourage insects, fungi, viruses or bacteria from entering these wounds.  Water the soil around the base of each tree while trying to keep the cracked trunks as dry as possible so that the tree will form calluses and seal off the injuries.

Below is some general information on the subject of yellowing and browning of cedars.  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 excellent source of information is:

 

https://www.mobot.org/gardeninghelp/plantfinder/hortline.asp?code=3360