The Mystery of the 'Toe'

It's the holidays, and around this time of year I can't help but think about  mistletoe.  That's right, mistletoe.  Mistletoe is the common name for over 20 genera of obligate hemi-parasitic plants of trees in the order Santalales.  Mistletoe still photosynthesizes to create carbohydrates for energy, but it uses structures called haustorium to penetrate tree branches, where it then absorbs water and nutrients directly from the tree. With heavy infestations comes tree decline, and affliction with mistletoe can contribute to tree death.  Branches with mistletoe can also become quite brittle.

Hickory branches afflicted with mistletoe.

The berries of mistletoe are a food source for many species of animals like birds, and is how the plant is distributed through out tree crowns.  Birds either wipe the berries from their beak on to branches, or the seeds survive ingestion and are distributed through bird droppings (poop). The berry itself is extremely sticky when squished.  Most mistletoe flowers are insect pollinated, but some have huge showy flowers which are bird pollinated.

Sticky toe berries.

Now if you thought all of that was interesting, the myth of mistletoe is something else.  Apparently the Norse god Loki tricked the blind god Höðr into killing his brother Baldr with a mistletoe arrow.  This was after Baldr and Höðr's mother, the goddess Frig, failed to get an oath from mistletoe to not harm Baldr.  She never asked mistletoe take the oath as it seemed 'too young.'  Lesson learned.  After bringing Baldr back to life, Frigga declared no harm could come to one standing under mistletoe.  Another myth states mistletoe was the wood that Christ's cross was made of, and after the crucifiction it was destined to live the rest of eternity as a parasite. 

Mistletoe is most famously sacred to the ancient Celtic Druids.  After sacrifices, mistletoe would be passed out, and the recipients were thought to have good fortune.  Mistletoe was thought to be the soul of the oak, and was collected at the summer and winter solstice.  It was also thought of as a sexual symbol.  Druid beliefs were adopted by early Christians and mistletoe was hung in homes to ward off demons.  This is where the modern practice of decorating with mistletoe during the holidays came from.

The Greeks had their own mistletoe tradition, and the plant was used during early marriage ceremonies as a sign of fertility.  This, combined with the Scandinavian tradition of standing under mistletoe as symbol of truce with enemies, is probably were the modern Western European kissing tradition evolved from.    

So mistletoe is pretty interesting on many different levels.  A word of warning though, if your mistletoe is allowed to touch the earth then it looses it's mystical powers.  Happy Toe hunting, and happy holidays.     

Toe harvesting is easiest done by aerial lift truck.

   

Conservation Arboriculture

Conservation arboriculture is neat.  It seems their are two main ideas behind conservation arboriculture.  The first, trees (especially urban trees) are of themselves complex ecosystems.  There are obvious and not so obvious examples of this.  Obvious examples are the vertebrates (ie. squirrels and birds) that use trees as their home and food source.  Then there are the not so obvious examples, like the invertebrates and fungi species that only a few may appreciate.  The bark alone can be home to arthropods, lichen, and fungi.   Taking an ecosystem view of a tree forces us as arborists to think of tree management differently.  For example, there are dozens of insect and fungi species that rely upon the dead wood in trees for survival, dead wood that an arborist would traditionally recommend for removal.  Conservation arboricultures teaches us their is an intrinsic value to these forms of life living in the tree.

The other idea behind conservation arboriculture, there is intrinsic value to very old trees.  Trees that we consider, due to structure or health issues, candidates for removal.  Some would call these ancient trees, and in places like the United Kingdom there are organizations dedicated to identifying and preserving these trees.  In my opinion the term 'ancient' is relative.  An ancient white oak may be 600 years old, while an ancient aspen may be 70 years old, but to me the idea is the same.  Older trees have a story to tell us, and the older they are, and the more perceived defects they have, the more likely they are to be the home of a variety of life.

As mentioned earlier conservation arboriculture challenges our tree management strategies.  Our first priority is always safety, but our question becomes how can we manage the perceived risk of our ancient urban/suburban trees while maintaining there vitality as a thriving multifaceted ecosystem?  In some cases it may be easy.  Moving a target or erecting a fence to keep people away from the fall zone.  In other cases it may be making the call on questionable reduction cuts, and leaving pieces of dead or dying branches in the tree that would normally be removed.  Would it be crazy to make reduction cuts on an already dead limb to reduce its chance of failure?  And still on our not so ancient trees, maybe we step back and let some deadwood build up or leave some smaller pieces in there.

This approach may not be for everybody, or every tree, but is an important idea to consider as we learn more about the trees we cherish.  Below is a link to an article written by Neville Fay which was run in Arborist News.  It is a real interesting read.
http://www.treeworks.co.uk/downloads/CONSERVATION_ARBORICULTURELearning_Review4-16-06-2011.pdf

The Angel Oak of Charleston, SC

Structural Root Decay: Another Reason to not be a Fan of High Nitrogen Fertilization

While browsing through Fungal Strategies of Wood Decay in Trees by Schwartze, Engels, and Mattheck, I came across an interesting piece of information.  The authors state decay progresses faster in wood with higher concentrations of nitrogen (N).  They then imply a correlation between high N fertilization and increased amount N in structural roots.  If these hold true applying fertilizers high in N, like many commercial tree and lawn companies, will actually speed up wood degradation by fungal decay agents and increase the risk of tree failure.

Now in cases where known root decay is present but not at the point where removal is considered necessary, some tree managers will recommend tree fertilization in an attempt to out grow, or at least stay pace with, the decay.  If the proper fertilizer analysis is not recommended we may actually be speeding up the decay process.  Custom fertilizing based upon the results of a soil sample is really the best practice when specific tree health goals are priority.

Mmmm nitrogen.

Lint Bug: The Aphid Wolf

Have you ever seen a lint bug?  Up until a few months ago I thought they were inconsequential, but cute,  little insects living on tree trunks.  I never really thought about what they ate, or their role in the ecosystem.

While doing research for another assignment I came across an article about lint bugs, and found they are brown lacewing larva.  As many of us know, green lace wing larva are voracious predators of many arthropod plant pests, and so are the larva of their brown winged cousins.  One web-site even referred to them as Aphid Wolfs.  They carry debris on their back for camouflage, and interestingly enough, some of that debris is actually body parts from their victims.  I might have a new favorite insect.

That gray pile of debris is a lint bug in a sea of  gloomy scale.

I snagged this close up picture from www.whatsthatbug.com

Red Maples: What a Bummer

By some twist of arboricultural fate I was charged with doing an 800 tree inventory this past week.  About 60% of the trees were.... you guessed it red maples.  Of these not one was with out co-dominate stems combined with some kind of defect.  Be it girdling roots, buried root collar, gloomy scale, or all of thee above.  Lets take a pictorial look at the mayhem.

So many co-dominate stems all coming from the same area on the tree.

A crack in the stem originating from co-dominate stems and leading almost to the ground.

Gloomy scales piled upon gloomy scales feeding upon there victim.

More sever cracks originating from co-dominate stems.

Of course a pictorial account of red maple defects would not be complete with out some impacted stem girdling roots.

Multiple upright branches with associated storm damage.

Left unattended since planting, these trees have become a maintenance nightmare.  Young tree pruning and proper planting are paramount, and this tree inventory is a prime argument.  To correctly mend these issues this home owners association will be looking at more than a $50,000 price tag.  Red maples, what a bummer right?

I Like Red Maples

Really I do, and at this time of year as their leaves are turning different shades of red, I can't help but think they are not as bad as many arborists make them out to be. Sure I've been known to role my eyes at thought of planting another 'October Glory,' but in October I wish I had one in my yard.

Red maples in the landscape get a bad wrap. They are produced in the millions by growers, and by the time they make it to retail there are layers of pot bound induced girdling roots, and the root flare is almost hopelessly buried. Lack of young tree pruning and disregard for proper crown structure leave them prone to co-dominate stems, included bark, and branch breakage. But aren't these true of many species by the time they make it in the landscape, and maybe we just notice it more on red maples because there is just that many more of them?

Red maples as a species are incredibly versatile. Native red maples grow through out the Eastern U.S. from low land swamps to rocky hillsides.  They are like a native super tree.  This species is planted in the landscape from Florida to British Columbia. Except for gloomy scale in the South East there are no more pest problems with red maple then with any other landscape tree. And even in the South it isn't uncommon to see a red maple planted to deep in a parking lot, with girdling roots, and covered in gloomy scale, and though not looking good, still surviving.  So take a break from hating on red maples and enjoy some fall color.

Trees Don't want to Die: A Musing

Trees have been around for millions of years, and they have found ways to survive outside in all kinds of conditions. We as humans try to understand why trees die and fail, and how to predict these events. Along the way our industry has come up with 'rules of thumb' to help us predict this. We hear arborists reference numbers like 30%, 33%, or 70% to quantify chances of tree failure or death, but trees break these rules on a daily basis.

There are 'high risk of failure' trees, condemned years ago, still standing today.  These trees have stood through wind and storms which have toppled other trees.  I've seen mature oaks with more than 50% of their trunk circumference damaged from the ground to 20-ft up the stem that are green and vigorous, and which have had enough energy to form callus tissue around the damage.

My view is becoming not, 'we have this much strength loss,' but instead 'we have this much strength left.'  And the same when it comes to the vascular tissue.  We must realize, of course, that some of this will be species, condition, and site dependent.  But, if a tree has 32% of it's root-flare compromised by decay is it a moderate risk of failure, while at 33% it is a high risk of failure?  Or, is what matters the 2 or 3 root flares not damaged are strong enough to support the weight of the tree even if even if all the other flares were compromised? How long will a tree with 50% of the stem girdled maintain a health canopy? 1yr, 5yrs, or 10yrs?  These are the questions I ask myself, because I don't want to remove a tree until it is necessary  and most of my clients feel the same way.

Notice how this tree has fallen completely over, and yet it continues to put out growth maintained by just a small portion of vascular tissue.

Tree Root Failure: A Discussion

Earlier this week an arborist friend and I were discussing root failure.  The discussion revolved around, if roots were severed, which direction would the tree fall.  His argument was the tree would fall towards the severed roots, while my argument was the tree would most likely fall away from the severed roots.  I believe my argument, the tree would most likely fall away from the severed roots is supported by a publication from the University of Georgia Root Strength  & Tree  Anchorage.

Root failure occurs in association with wind load and gravity.  'Beyond the root plate area, root tensile strength becomes more critical to anchorage.'  That is, as the wind blows roots on the wind ward side of the tree, the tension roots, are doing the most work.  Relatively speaking of course.  If these roots should be severed or damaged the tree would fail in on the opposite side of the force, or away from the root damage. Mattheck describes the roots on the tension side of the tree as forming holding knots in the soil.  Again, considering damage to the tension side of the tree will give a hint to where the tree may fall.

In addition to these references, I have also seen trees that are root decayed fall opposite the decay.  Now I could be wrong in my conclusion, but I think I make a pretty good case.  Some other interesting information from the UGA publication:

-'To summarize, a few large diameter and long roots can not provide effective resistance to failure.  It is in the proliferation of smaller roots in consolidation of the root plate which provides anchorage success.  (Stufka & Kodrik 2008)'

- 'Compression strength increases for a short distance from the stem base before declining with length.  Root compressive strength was found to be roughly the same for angiosperms and gymnosperms, but bending strength was found to be much greater in angiosperms. (Stokes & Mattheck 1996)'

-'Anchorage is concentrated in two general locations around a tree base: 1)  close to the stem base on the
leeward side and focused on several large diameter roots; and,  2) farther away from the stem base on the windward side in many, smaller, large surface area, near-surface roots.  (Danjon et.al. 2005)'

-'Windward roots have forces applied which are concentrated approximately 1.5X (one and one-half times) farther away from the stem base than leeward roots.  (Stokes 1999)'

Lions Tailing: How not to prune

Lions tailing is when interior branches and sprouts are removed along a stem or trunk.  This is an incorrect pruning practice because these interior branches are functional parts of the tree.  These branches produce carbohydrates that help with branch/stem taper.  Branches/stems with good taper are less prune to failure during storm events vs. branches/stems that have little variance in stem diameter throughout their length.    

During hot days leaves on the exterior of the crown close their stomates to prevent water loss.  While stomates are closed photosynthesis stops, and these leaves no longer produce food.  However, these exterior leaves shade the interior of the canopy, keeping it cool. The interior leaves will continue photosynthesis.  

There are few reasons to prune branches on the interior of the canopy outside of pruning crossing and rubbing branches.  If crown thinning is required, the cuts should be made closer to the branch ends to help alleviate weight on the branch (in my opinion).

While the picture below isn't great, it is a good example of what not to do when pruning a branch.  Wedding decorations are being hung from this branch, so we may be lenient on the arborist that performed the pruning.

Armillaria: Tree Failure

Armillaria, or honey fungus, is a genus that covers several species of soil born root decay fungi.  The common name is derived from the yellow-orangish mushrooms depicted in the pictures below.  Armillaria causes a white rot, which like Inonotus (as described in an earlier post) begins by breaking down lignin and in advanced stages breaks down cellulose and hemicellulose.   

While white rots are usually described as slow moving decay organisms, Armillaria is noted as being more aggressive in its attack on tree structure.  Armillaria gets its other common name 'black shoe string fungus' from the black mycelial fans it puts out to devour wood.  Unlike other structural root decay fungi, Armillaria also can affect the vascular system of the tree, so early signs of infection may be noticed by a decrease in tree vigor and poor tree health.

The pictures below show what happens to trees in advanced stages of Armillaria infection.

The yellowish orange mushrooms of Armillaria protruding from the bark on  the lower stem of the tree.

Notice the tell tale black mycellium penetrating the wood fibers of it's victim.

Reduction of a Silver Maple

I am a firm believer that we can save more mature trees with defects.  Large mature trees provide us with a higher quality of ecosystem services than small trees.  I am not saying we shouldn't be planting trees, but what I am saying, is there are options for retaining our larger trees that some would consider a hazard.

The pictures below are case in point.  This silver maple, thought of as a weak wooded species, has a large cavity in the lower stem, and several decayed root flares.  Three years ago, instead of removing the tree, a drastic crown reduction was performed.  Over all crown weight and height was reduced, not topped out.  The tree still stands today, now shorter, but better protected by wind and weather by its neighboring mature trees.  The concept is basic, shorter and lighter objects are less likely to fall over.

I tell everyone the same thing, "trees don't want to fall over." But, as with everything tree species, age, size, and vitality play into whether or not this is an appropriate treatment based upon the perceived defects.

The arrows point out specific large pruning cuts 

Topped Beech

Simply stated, it should be a crime to top a European beech.

I still love the irony that people think they are making the tree 'safer,' even though the sprouts that form as a panic response are more prone to failure. Boo to this homeowner and what ever hack did the job.

Fall Fungi

As the cool nights and mornings of fall slowly begin creeping in, and we once again are blessed by regular precipitation, start looking at the base if your trees. 

Last week Inonotus dryadeus conks began appearing along the base of willow oaks here in Charlotte.  These conks are the tell tail sign of root decay.  Inonotus causes a white rot which breaks down lignin, a structural component of wood, in the tree.

Many people believe that the amount and placement of decay conks is representative of the amount of decay found in a tree.  While that is usually false, it does hold true with Inonotus.  This is definitely something that needs to be considered when assessing trees with these conks present.

The Case for Proper Pruning

This tree was pruned in Feb 2012, and these cuts were made at the same time.  Notice how the bottom 2 were made correctly just outside the branch collar and are healing nicely.  The top cut was left as a stub, a short stub, but a stub all the same.  This cut shows no sign of callus tissue.

This is a great example of why proper pruning is essential.  This stub is now an entranceway for decay fungi for years to come.  Keep an eye on your cuts everyone.

The Case for Structural Pruning

Here we can see the results of a tree allowed to mature with no previous thoughts of crown structure.  You can see how one side of the tree was completely ripped of exposing internal decay.

An over-extended co-dominate stem combined with some internal decay resulted in this trees demise.  If care had been taken earlier in the life of this tree to prune for one dominate leader, and well placed scaffold limbs, this tree would still be intact.

Compaction for the Sake of Grass?

One of my favorite calls is from a contractor, in this case a very large landscape company, that has been busted by the city for failing to do any tree protection.

So our assignment is to decompact areas leveled for the sake of sod installation.  Our medium is compacted red clay.  If you have used an AirKife or Airspade in this scenario then you know attacking glazed clay is futile.  I go about it by finding an area where I can penetrate the soil as close to the severe compaction as possible.  Once deep in the soil,  I angle the air tool under the glazed area.of compaction.  By repeating these steps around the area, it eventually begins to break up in to large peds.

In the past I would try to break up peds into finer soil, but after having gone to Jim Urban's 'Up by Roots,' I now try to preserve peds.  These peds are an essential part of soil structure, especially in heavy clay soils.  Of course, I then mix in composted organic material to help maintain soil structure and improve nutrient holding and water holding capacity.

An argument may by made that August is not the best time to be using an AirKnife in such a large area, as it may dessicate fine roots.  In the face of progress, there are only so many options.

Roots and Backhoes

We were called out because the developer wanted to save this tree... after,of course, they already prepped the area for the new retaining wall.

The minimum safe distance for trenching on one side of this 40 inch plus Southern red oak according to industry standards should be around 12ft.  This excavation is about 7ft away from the trunk.

Tree health is no longer a concern, instead this tree has been made a potential hazard.  This picture is a good view of the amount of root mass under the soil.

Irrigation and Poor Drainage

Last week I wrote about the importance of water management, and the difficulty of getting it right in poorly drained soils.
This picture illustrates that point perfectly.  The arborvitae that looks the worst is sitting in the lowest spot of the planting area.  Drip irrigation is present, and run diligently a few times a week in a heavy clay soil.

Wax Scale

Here a picture of an Indian wax scale on a white mulberry.  Wax scales are interesting, as they are all female. That's right no males. It's kinda weird.

In mass, wax scales can stress out a tree or shrub, and produce copious amounts of honeydew, though I have seen neither.

The best management strategy is to simply pick them off in winter.

Vertical Root

We have been working with a local builder on some tree preservation.  This picture is of a vertical sinker root and parent root about 15 feet from the base a 40 inch+ willow oak.  The top of the horizontal root is about 2 feet below grade.
Maybe not the greatest picture, but a rare glimpse of tree structure within the soil.

Structural Pruning

I went to the NC Urban Forestry Council's annual conference yesterday, and had the opportunity to here Dr. Ed Gilman speak about one of my favorite topics... Structural pruning.  Now I must admit, while I enjoy listening to Dr. Gilman and I love the topic, I felt like sitting through another lecture on structural pruning was a bit below me. I was pleasantly proven wrong.  Here are some of the highlights:

- Pictures presented displayed a tree just before being thinned, just after being thinned, and the same tree 12 months later.  Twelve months after thinning the tree looked almost identical to just before it was thinned.  The conclusion is, thinning trees may not be the best practice when attempting to abate the risk of branch/whole tree failure.

- Don't be afraid to remove over 50% of a tree's canopy when structural pruning at planting to promote a "hyper" central lead.  Young trees recover fast from pruning.  Removing or subordinating all competing branches at planting will guide good tree structure for some time.  Competing branches can actually shade out the central leader, weakening it, and this may contribute to branch failure in the future.

- Don't be afraid to make big cuts to remove or subordinate competing branches on medium size trees.  Again, Dr. Gilman presented pictures of aggressive cuts, and how the tree recovered with much improved structure a few years down the road.

- Dr. Gilman introduced the idea of aspect ratio when it comes to branch size.  Lateral/secondary branches should be smaller in diameter (smaller in aspect ratio) then their parent stem, and the smaller the better.  Branches with larger aspect ratios are at greater chance of failure.  Ideal aspect ratio was not specified, but smaller the better was the conclusion.

- Finally, we where shown video of a tree before canopy reduction being blown by a dynamic wind load machine.  There was about 12 inches of play at about 1/2 way up the stem.  The same tree was then pruned to reduce about 30% of the branches from the crown.  The tree then had about 3-4 inches of play at about 1/2 way up the stem.  We may relate this data to individual large branches in trees with stem and root defects.  If we reduced all large branches by 30% on tall trees with defects that may predispose the tree to failure, then we may be able to retain more trees vs. removing them.  Awesome!

As with everything, we must take in to consideration the tree's species, condition, and the site when applying this data in the field.  Never the less, a great presentation, and I can't wait to get out there to get my structural prune on. 

Compacted Soils

There is no question that trees growing in compacted soils generally won't grow as well as trees in a lower bulk density soil.  Compacted soils adversely affect root tip elongation, affect gas exchange, and disrupt water availability.

In the latest edition of Arboriculture and Urban Forestry a study performed by Barbara A. Fair, James D. Metzger, and James Vent  concludes  water availability in compacted soils may be the limiting factor for tree growth.  They found carbon dioxide levels were 5-18 times higher in compacted soils compared to atmospheric concentrations, while O2 concentrations were similar to atmospheric levels despite density.

This tells us that water management is increasingly important in our urban landscapes.  Often tree owners tell me they irrigate, but the irrigation is usually too little or way too much based upon the site.  Getting the correct amount of water in compacted soils can be a tricky code to break.  Think of a line of plants along a slight grade change.  Many times you will see the trees on the high side parched for water, while the trees in the low area are sitting in saturated soils well above field capacity.

To Stub or not to Stub?

For decades we were taught to prune all limbs, big or small, at the branch collar.  However, over the past few years a debate has been growing about what to do when pruning large limbs.  Some would argue that when removing large branches or stems it is better practice to leave a stub.  The thought is by leaving a stub, decay organisms would take more time to enter the parent stem, thus offsetting internal decay and structural weakness for some time.

I have debated this in my head for years, but recently while reading Fungal Strategies of Wood Decay in Trees by Schwartze, Engels, and Mattheck, I came across these lines.  "After removal of a branch, this cut surface is like a chemical battlefield, as not only spores of wood decay fungi germinate there but also the spores of many other fungi, e.g. the mold fungi.  Because of the competitive pressure and interplay of different fungi, it is much more difficult for wood decay fungi to become established on such a substraight..."  It goes on to say that leaving a  large stub allows more potential for wood decay to become established, and once established, wood decay is difficult to slow down.

Now of course, tree species and specific wood decay organisms all play a part. From the conservation biology point of view, large declining stubs are also home for many species of arthropods and fungi that would otherwise not have a home, so there may be some intrinsic value.  With that in mind, site use and targets may come in to play.