Red branches, thinning needles, shedding bark–these are all signs and symptoms of a Douglas fir in distress. So, what can you do about it? If your tree is showing signs of failing health, you’ve come to the right place. In this article, we’ll talk about how to tell if a Douglas fir is healthy or unhealthy, as well as what to do for a tree that is slowly dying.
What You'll Learn Today
- How to Tell if a Douglas Fir is Healthy?
- How to Tell if a Douglas Fir is Unhealthy?
- How to Save a Dying Douglas Fir?
How to Tell if a Douglas Fir is Healthy?
The first step to identifying potential problems with the trees on your property is to know how they should look. How can you know if your Douglas fir is healthy or if you should be concerned about it?
Below are several signs that point to a healthy tree. Before reading the list, you can check out this video to get a good visual on what healthy Douglas firs should look like:
Douglas firs are generally quite dense–they have thick branches with thick needles on the branch. This is especially true of the small varieties often used in landscaping and sold as Christmas trees.
Douglas firs found growing on the West Coast and in the temperate rainforests of the northwest often grow much larger than the interior varieties more commonly used in landscaping. These coastal trees may not look as dense, especially closer to the ground, as they will shed their lower branches as they grow.
Deep Green or Blue-Green Color
Douglas firs have a deep, dark, rich evergreen color. The needles should be a deep forest green to blue-green.
The entire tree should be fairly uniform in color. A close inspection of the branches should show rows of needles that are uniformly green; if many of the needles are beginning to turn brown, this could be a sign of poor health.
Few Dead Branches
As mentioned above, some Douglas firs will shed their lower branches as they grow; this is especially true of coastal trees growing in forests or stands with other Douglas firs. This is a perfectly normal process.
That said, a healthy tree should not have a lot of dead branches still attached. It is normal for a tree to occasionally have a branch die, but if it is happening frequently, this may be cause for concern.
A good way to examine your tree’s overall health is to check the trunk. Look for damage such as holes, cracks, soft or darkened areas, and missing bark.
A healthy Douglas fir will have a healthy, undamaged trunk. Any signs of damage could be a point of weakness where disease or pests could enter.
What’s more, even small areas of rot or fungus on the trunk could easily spread to other parts of the tree.
Douglas fir trees need moist but well-draining soil that is neutral to slightly acidic. They do not tolerate drought very well, but they prefer warm summers and cold winters as well as full to partial sun.
If they are growing in hard, compacted soil, marshland, more extreme climates, or shady areas, they may look fine for a period of time; but eventually, they will begin showing signs of poor health.
If your tree has a less-than-ideal growing environment, you can expect that it will not live as long as you would like and that its health will deteriorate over time.
How to Tell if a Douglas Fir is Unhealthy?
So, what are some signs of an unhealthy Douglas fir? How can you know when it’s time to take action to save your tree?
According to Oregon State University’s Extension Service, here are some common signs and symptoms of a Douglas fir in failing health.
Sparse or Thinning Foliage
If your tree is shedding needles at an alarming rate, looking less thick and bushy than it used to, then it could be affected by a number of pests, diseases, and environmental factors.
This is often one of the first signs that a tree is losing its health.
Take a close look at the tree branches, then step back and examine the tree as a whole. Do the branches look less bushy than they used to?
Does the tree overall have a thinner, more sickly looking appearance?
If so, these symptoms may be caused by both drought and overwatering, diseases such as laminated root rot and armillaria, and pests such as the flathead borer and Douglas fir insects.
This symptom may also be caused by a condition known as needle casting. This is a disease that affects an evergreen’s needles, causing them to die and slowly killing the tree.
Discolored foliage is another early sign that could point to a number of problems.
Are your tree’s needles turning a lighter green or yellow? In severe cases they may even turn orange, red, or brown.
Remember, Douglas firs are evergreens; these changes to their foliage are unnatural.
Causes of these changes are the same as those outlined above: under- and overwatering, diseases, pests, and needle casting.
Treetop Looks Dead
What if just the top part of your tree starts dying? The lower branches of the tree look fine, but the upper tip and its surrounding branches may turn brown and lose their needles.
What causes this?
There are a variety of insect pests that can cause this phenomenon. Some of these pests include twig weevils, engraver beetles, and borers.
If insects are not the cause, your tree may have a disease called phomopsis canker. This disease, as the name suggests, can cause cankers on the tree branches and may also cause the tops of the tree to die; that said, it will rarely kill the whole tree unless the tree is quite young.
Dead or Dying Branches
If branches on your tree are dying, it is almost always the result of pests or phomopsis canker.
Some pests that can cause individual branch death include flathead borers, engraver beetles, and Douglas fir twig weevils.
If the entire branch, needles and stem, turns red, this could also be a sign of the insects discussed above, as well as phomopsis canker.
Loss of Bark
If your tree is losing great chunks of bark, leaving bare patches on the tree trunk, then a variety of factors could be to blame.
Trees that are suffering from drought conditions often begin shedding their bark along with their needles.
This condition could also be caused by borers in the trunk, as well as a variety of diseases such as blackstain and laminated root rot.
If woodpeckers are pecking at your tree, they are likely looking for insects inside.
Therefore, if you have woodpeckers, there’s a good chance your tree is infected with flatheaded or other types of borers.
Whole Tree Looks Dead
This is usually one of the last signs that your tree is sick. If it gets to the point where the whole tree appears dead, it may be too late to save it.
Again, tree death can be caused by a number of issues, such as pests, diseases, and under- or overwatering.
That said, if you catch the problem early enough, there’s a good chance you will be able to prevent it from progressing to this point.
How to Save a Dying Douglas Fir?
So now, you may be wondering, what can you do? If you’ve identified an unhealthy tree on your property, there are several things you can do to try and save it.
Douglas firs should be watered on a regular basis to keep the soil moist, but you don’t want it to be soggy. Water about once a week to once a month depending on how much rain you get in your area, and check the soil often to make sure it is neither too wet nor too dry.
Prune if Necessary
If you notice dead or dying branches, prune them away. Sometimes restoring a tree’s health is as simple as removing the parts that are sick.
Acidify the Soil
Use a pH tester to check the soil quality around your tree. If it is above 7.0 (neutral), you may want to add something to the soil to lower its pH.
Some of the things you can add to acidify the soil include:
- Acidic fertilizer
- Iron sulfate
- Sphagnum peat moss
- Ammonium sulfate
Trim Surrounding Trees
Douglas firs need full to partial sunlight. If you have young trees that are surrounded by other, taller trees that are blocking out the light, you may want to thin out these other trees so more sunlight can get through.
Treat for Pests
If you suspect you have borers, twig weevils, or engraver beetles, it might be good to get a professional arborist out to confirm your suspicion. The arborist will be able to identify the specific pest targeting your tree and recommend a good product to use to get rid of this pest.
Treat for Diseases
The same is true if you suspect a disease. Check with a professional arborist to see if they can identify the specific disease and a product that will clear it up.
Healthy Douglas firs will have thickly-needled, dark green or blue-green branches, undamaged trunks, and few or no dead branches. There are a number of environmental factors, diseases, and pests that can harm Douglas firs, so if your tree is looking less than healthy, it may be time to take action.