Mistletoe may be good for those desiring a kiss but not so much for your trees…
We see a lot of mistletoe around here. Unfortunately, that doesn’t mean that love and lingering holiday cheer are in the air, but rather, that the seeds propagating the parasite are soon to be airborne. (And watch out: Mistletoe seeds are ejected from the plant at speeds of up to 60 mph!) It’s something to be aware of as mistletoe is detrimental to the health of your trees.
Note the abnormal branch growth of the witches broom on this fir. Photo by Cephas via Wikimedia Commons
North Idaho is home to a handful of dwarf mistletoes that are specific to our native trees. Larch, Douglas fir, ponderosa and lodgepole pines are all primary host species. In our work, we have seen it most often in larch and Douglas fir.
What does mistletoe look like? It’s most easily spotted when the infection is full-blown and affected limbs have witch-broomed in response. A witches broom is a mass of chaotic branch growth that appears as a dense clump in your otherwise well-formed conifer. The witches broom is a response to the mistletoe but not the mistletoe itself.
Larch dwarf mistletoe shoots begin to sprout in the spring eventually forming clusters of shoots as seen in this plant. Photo courtesy of the USDA Forest Service Archive
Mistletoe is hard to detect early on. For several years, no outward symptoms may be apparent. This is known as a latent infection. After several years, though, scaly shoots emerge. However, since they are only two inches tall and are likely hidden in the canopy of the tree, most property owners don’t notice the early stages of mistletoe infection. Thus, we are often called in to treat more heavily infected trees that have had many years to spread the parasite to surrounding trees. This makes mistletoe eradication difficult.
Mistletoe harms trees in numerous ways. For one, as a parasite, it takes water and nutrients from the tree for its own growth, leaving the tree weaker and more susceptible to other insect and fungal invaders. Infected trees grow slowly, and heavy witch-broomed limbs are prone to breakage due to their weight. Mistletoe often leads to tree death. It also creates a fire hazard. All of this means that a mistletoe infested tree is a hazardous tree.
Our approach to mistletoe treatment is to first assess the tree to determine if the tree is a candidate for pruning or removal. If the infection isn’t too severe, pruning of witches brooms and less affected limbs will be undertaken. Healthy looking limbs adjacent to infected ones may also be removed in case infection is latent. Pruning in subsequent years may be necessary to catch future outbreaks. And pruning is best undertaken in the early spring or late fall when pollen and seeds are not being released from the mistletoe. We don’t want to inadvertently spread more infection.
One last thing to consider is that mistletoe does have its uses. Various birds and forest animals use witch-broomed limbs for cover and as nesting sites. We once found ourselves in a tree, dodging a group of flying squirrels leaping to safety. There is something to be said for leaving an infected tree alone if it is not a direct hazard to you and the health of your forest.
If you have concerns about mistletoe, give us a call for an assessment. And for more information, there are several helpful publications online:
Thinking of topping your trees? Think again…
At least once a month, we get a request for topping someone’s trees. The reasons are myriad: The tree is blocking the view, it’s impinging on satellite service, it’s deemed too tall and hazardous, or someone just likes the look. On the surface, topping doesn’t seem like a bad idea. You get to keep your tree and have it out of your way. In reality, though, topping is a terrible practice, and we try to dissuade all our clients from having it done.
These Norway spruce trees will be unable to heal over the wounds that topping created, thus leading to rot and structurally unsound trees.
Why is topping so bad? There are a lot of reasons, but first and foremost is that it will likely kill your tree. Hacking it back may not kill it this year or next, but your tree’s lifespan will definitely be shortened.
Topping drastically reduces a tree’s leaf mass, limiting the tree’s ability to produce food and sustain itself. This causes root dieback. Also, the site of an indiscriminate topping cut can provide access to decay, insects, and disease. And limbs newly exposed to sun without the protection of the canopy may become sunburned, leading to cankers and branch death. All of this leads to an unhealthy, unstable tree.
Furthermore, topping often leads to something we call “witchbrooming.” This is where a multitude of branches sprout from near the cut. These epicormic branches are weakly attached and can grow up to 20 feet in one year. Such limbs are susceptible to breakage in storms, causing more damage than the tree originally would have.
Another problem with topping is that it will ultimately cost you more in the long run. More frequent pruning will be necessary to mitigate branch failure risks and to rein in the height of the new epicormic branches. Furthermore, as the tree’s health declines, it may just have to be removed after a number of years.
It’s no surprise that such extensive topping killed this tree. If you want to cut a tree back that much, it’s better to just remove it entirely.
Finally, topped trees are ugly. When you consider that healthy, well-maintained trees can add 10-20 percent to the value of your property – and topped trees can be seen as a safety risk – why would any homeowner request the practice?
However, there are healthy approaches to canopy reduction. One method is called “drop-crotching,” where tall limbs are cut back to an appropriate branch that can take on a terminal role. This branch must be at least one-third the size of the one removed. Drop-crotching can diminish height while maintaining the shape and health of a tree. However, this is only appropriate for trees with a rounded, or decurrent, shape. Pyramidal, or excurrent, trees (think conifers) simply cannot have their height reduced without negative consequences.
In some cases, the best practice is to remove the problem tree and replace it with one better suited to the site.
If you are considering topping your tree, please give us a call. We can offer alternative approaches that may solve the problem at hand.
For more information, read “The Myth of Tree Topping,” from PlantAmnesty, “Why Topping Hurts Trees,” from the International Society for Arboriculture, or “What’s Wrong with Topping Trees?” from Purdue University.
Utilizing proper pruning techniques can save you money down the road…
Many of the big, expensive jobs that come our way are the result of improper pruning practices. Though these expensive jobs are good for our bottom line, we’d rather see our town populated with healthy, thriving trees, the result of proper pruning.
This tree was once topped, and it has now sprouted back with a vengeance. These epicormic branches tend to be weakly attached to the tree, causing problems with falling limbs later.
Why is proper pruning so important? And why does improper pruning lead to expensive remedies? Improperly pruned trees cause excessive wounding and resultant rot, decreased food production which weakens the tree, increased sprouting that leads to weak branch unions, and increased chances of wind, ice, and sun damage. Thus, a tree that is not properly pruned is more likely to die or to drop limbs. These limbs—or the entire tree—must be removed, at a greater cost to the tree owner than properly pruning at the outset.
The most common improper pruning practice we see is the topping of trees.
These topped trees are unlikely to survive long. Such drastic pruning practices are never acceptable.
This is where the limbs are cut back close to the trunk in order to decrease the height of a tree. Many people do this in order to improve views or satellite reception, to decrease shade in the yard, or to get rid of some of the “mess” that trees create (leaves, fruit, etc.). In all of these situations, we recommend simply removing the tree. It is better for the tree—and your bottom line—to cut it at the base than to leave it weakened and dangerous.
The International Society of Arboriculture has several brochures on the proper pruning of trees; Pruning Mature Trees and Pruning Young Trees are both worth looking at if you’re considering taking on tree pruning yourself. However, if you have any trepidation about tackling a pruning project, don’t hesitate to call us. It’s much less expensive to properly prune a tree than it is to remedy the damage done by improper pruning practices.
The moment you think about tree pruning is the time to act…
It’s a common question among our clients: When is the best time for pruning my trees? And it’s a question with as many answers as there are people who care to comment. There are kernels of truth to ideas that some trees prefer pruning at some times over others, and that tree pruning at various times of the year produces different effects. However, the answer can generally be kept fairly simple: When you remember that your tree needs pruning, that’s when you should do it. Your tree is healthier pruned, no matter the time of year.
This willow is safer and healthier now that dead limbs have been removed. Tree pruning is vital for tree health.
Removal of dead, diseased or problem limbs can be undertaken at any time without negatively affecting the tree. This makes up the bulk of tree pruning requests. Sometimes, though, people simply want their tree cleaned up and thinned out a bit (and kudos to them for seeing the importance of such maintenance!). Attending to this in late winter or early spring – before the buds swell – will maximize growth in the coming year. Conversely, pruning during or soon after the leaves come out can retard growth. The tree has just expended most of its energy in putting out new shoots and leaves, so it has few resources left to compensate for what has been removed. Normally this isn’t a problem, but if too much is removed during this time of major energy output, the tree can become stressed and, thus, more susceptible to disease.
Pruning when the tree is dormant – after it has lost its leaves and before buds swell in the spring – allows the tree the most time and energy for healing its wounds. It gets a full growing season to compartmentalize those pruning points. Furthermore, at the time of tree pruning, pests are also dormant and won’t use the wounds as points of entry.
Fruit and other flowering trees can be pruned at various times to various effect, depending on your desire to enhance flowering, develop proper structure, or thin fruit. Other trees may be susceptible to certain pathogens that follow particular transmission schedules, so pruning is generally avoided during this time.
All of this aside, though, we can’t emphasize enough that one of the most important things you can do for the health of your tree is to keep it properly pruned. No matter the tree, no matter the season, if you look out your window and are reminded that your tree is in need of a little TLC, give us a call. We will come out and assess the tree, as well as provide a free tree pruning estimate. If we determine the tree would be best left alone for a few weeks before pruning, we’ll let you know. Just make the call. Your tree will thank you with a long and productive life.
Root problems might be simmering under the forest floor, waiting to topple your trees…
Root problems are the most difficult hazards to detect because most of the problem is underground and out of sight. People often have to wait for the visible portion of the tree to be affected before determining that there are root problems. Above-ground signs of root problems might include dieback, discolored needles or leaves, leaning with recent root exposure, as well as soil heaving, conks, or sap flow near the base of the tree. Also, failing trees nearby could indicate that the still-thriving trees might have a root problem.
Roots are essential to the structural support of your trees. They literally hold your tree to the earth. Thus, when root systems begin to fail, trees become a hazard to nearby people and property. Root problems may lead to blow-down in windstorms or tipping over without warning under the weight of leaves in the summer. Root problems are often silent but carry deadly consequences.
Decay fungi often indicate that a root problem is present.
There are two types of root problems: physical and biological. Decay fungi often cause biological root problems. This becomes evident when conks appear near a tree’s roots and in nearby decayed stumps. However, only about half of the trees infected with root rot might show symptoms at any one time. In this region, grand fir and Douglas fir are particularly prone to laminated root rot. Idaho Department of Lands provides an excellent and informative explanation of laminated root rot.
Physical root problems are often human-caused. They include severed, loosened, cracked, broken and exposed roots. Construction or paving near a tree, driving vehicles over roots (soil compaction), and raising or lowering the soil level near a tree can all cause physical root problems. In attempting to diagnose a failing tree, we may ask you questions about recent activity on your property. If you’ve just constructed an addition to your house or have rerouted your driveway or plumbing, that might be the problem.
One final physical root problem that is not human-caused is the girdling root. These roots grow around or across the trunk or other roots on the tree. As the tree grows, girdling roots may begin to choke the tree, reducing its ability to take in water and nutrients. Symptoms are similar to those you might see in drought, including early fall color and dieback.
Of all of these issues, the symptom you should be most concerned about is a tree demonstrating an increased lean with cracking or mounding soil at the base. This is a serious hazard and should be dealt with immediately, before it falls on its own…because it will soon fall. Even if you only suspect root problems in one of your struggling trees, give us a call. We’re happy to provide an assessment and free estimate.
For more information about root diseases, go to the Forest and Shade Tree Pathology website. And to learn more about your potential hazard trees, don’t hesitate to contact us.
Cankers are often quite visible, but cause and treatment aren’t always straightforward…
Cankers tend to be prominent. If your tree has a potentially hazardous canker, it’s hard to miss. Think of the tree version of a large, open wound or deformity, and you’ve got the visual idea of cankers. They may be ugly, but are they a problem? Maybe yes, maybe no. And maybe not quite yet.
An older callused canker on a paper birch. Photo courtesy Markus Hagenlocher via Wikimedia Commons.
Visually speaking, cankers are places on the trunk or branch of a tree where the bark is sunken or missing. They can lead to hazardous situations, creating weak spots where breakage can occur. Of most concern are cankers that affect more than 120 degrees of the tree’s circumference or cankers connected to other tree defects (e.g., cracks, weak branch unions, or cavities). Also of concern are cankers that are either directly facing or opposing prevailing winds.
Note the callus formed on the canker on this spruce tree. Photo courtesy Сыроежкин via Wikimedia Commons.
Cankers are typically caused by bark-inhabiting pathogens (usually fungal or bacterial), but sunscald and frost can also cause cankers by killing patches of bark. And while a wound on a tree (an improperly cut branch or a damaged place on the trunk) won’t directly lead to a canker, it can be the entry point for pathogens that will.
Cankers can either be annual or perennial. The annual ones are handled in a single year by a healthy tree, which grows a callus over the affected area. A perennial canker returns year after year, growing slightly bigger in the process. The pathogens attack the callus each year, meaning the tree has to start over again. These cankers often have the look of a target on the face of a tree, exhibiting concentric circles. Though these cankers may be visually unappealing, they are slow-growing, and you may be able to enjoy your affected tree for years to come.
What you really need to be concerned about is canker rot. This is when the canker is actually associated with fungi that is decaying wood inside the trunk of the tree. Thus, you have the combined issue of poor internal structure (from the rot inside the tree) and dead bark and tissues on the outside of the tree. Trees exhibiting canker rot are very hazardous and should be dealt with immediately.
Cankers come in all shapes, sizes, and can be from scores of different pathogens. Often, we can’t pinpoint how exactly the canker came about, but we can assess your tree and let you know if the canker is simply an eyesore or a true hazard.
For more information on cankers, the Forest and Shade Tree Pathology website is absolutely the best place to go…and it will make your head spin with all the scientific information they have to share. For an overview, go to their Cankers page, and to learn about specific diseases, go to Cankers on Parade.