Question
QUESTION: In doing a search about possbiel causes of the 100 year old dogwood in my yeard, I ran across an old question (http://en.allexperts.com/q/Trees-739/Dogwood-trees-blooming.htm).  My pionk dogwood has been realatively healthy until recently.  I've noticed more and more limbs dead and what is flowering/bearing leaves is thinning.  Last year I hired Scott's lawn service for fertilizing and weed control which they do year round 5x a year.  I'm wondering if it is the cause of my tree's unhealthy look (or could it be the tree's age and the fact it has a significantly hollow area to is trunk?).    I had a tree trimmer come out to trim some of the dead limbs but he said it is dying and needed to come down - trimming it would leave it with so few limbs that it would be unsightly.  I will provide any information that you need.The county agricultural extension officer is due to pay me a visit next week.

ANSWER: If the product used is a granular weed and feed product this will damage trees. The hollow is not causing the problem--the living part of a tree is just under the bark and the rest is dead woody cells. When a trees bark is damaged decay fungi can enter the wood and over time decay the wood causing the hollow. This hollow can weaken the trunk causing breakage during wind storms. There are several diseases that can cause dogwood problems one is dogwood anthracnose.  You should see the leaves hanging on the branches and not falling off as they normally do if this disease is the problem. Fertilizer will help but this tree is reaching the end of its life expectancy if it is 100 years old. I would try 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. Fertilize just before a rain storm and you will not have to water it in. Here is a web link to information on anthracnose. The Extension specialist after looking at the tree should be a great help.

http://www.na.fs.fed.us/spfo/pubs/howtos/ht_dogwd/ht_dog.htmt

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QUESTION: Thanks!  I did as you instructed.  The local Co-Op only had 15-15-15 so I cut the volume back a bit.  

Can you give a conservative estimate on how long should it should take for the tree to turn around/improve?

Answer
You should see some improvement in a few months in the away of greener foliage but it may take next spring to see any additional improvement in an increase in the amount of foliage. The spring is the time tree put on most of the new growth so you may see some new growth in new leaves this year but not as much as next spring. What the fertilizer does is increase the root growth and in turn the increase root growth increases the foliage growth.