Past living Christmas trees (Douglas firs) declining
We have 5 Douglas firs which we purchased with the root balls as Christmas trees over the 16 years in our house. The tallest (oldest I think) is 20-25 ft. high and has lost all needles on the top half of the tree. The process has been occurring over the last few years. After reading about the 2 diseases which most often affect Douglas firs, I'm guessing it has been infected by one of those diseases.
Is the tree salvageable? If so, what would you suggest doing? Can a tree grow back the needles as it "recovers" from disease? My husband has noticed another Douglas fir on one side of the diseased tree beginning to thin out. I'm assuming the diseases can travel between trees as they are planted 20' or so apart. Should we have all the trees treated for disease? We haven't fed the trees in several years. Could that be a reason they might now be prone to disease? Do you know of any reputable tree services in the Frederick area?
The diseases that infect the needles of Douglas firs do not start at the top of the tree. They tend to appear all over the tree or from the bottom and move up. Our plant pathologist did not recommend treating the trees.
Top dieback such as you are seeing points to damage from root death and that can be caused by drought killing the roots or a root rot. This is, unfortunately, common in Douglas firs because they are not really compatible with Maryland's climate over a period of years. They tend to grow well for a number of years and then, as they get bigger and their water needs get bigger, they slowly weaken and die.
You can certainly take a close look at the dying (not already dead) needles and see if there are obvious spotting or infection. But it is more likely that your firs have just reached a size that is not sustainable with the high summer temperatures and humidity of this region. Douglas firs are native to the higher altitudes in the western mountains.
If you remove the dead top of the tree, the bottom may live for years, but it will not regenerate a nice shape.
Can you advise what pines if any, that are sold as root balled trees would do well in our climate? We are considering Scotch and Norway pines. Thank you!
By saying 'pines' we assume you mean evergreen trees that are commonly used for Christmas trees? There is a Norway Pine, but it is Norway Spruce that is often grown in Maryland. It is a good alternative. Scotch pines have some disease problems, so we wouldn't recommend them.
White pines grow well here and are customary for some. They have long, soft needles, but weak branches for hanging ornaments.
Any tree you select will need to be carefully planted in a well-suited site with plenty of space to grow to maturity. Watering it well during the first couple years of establishment is of vital importance.
Take a look at this publication for further details: http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/not_updated/hg46_003...