The Root Collar, Oh No

By now we all know trees in the landscape, big or small, should have an exposed root collar. The root collar is the area of the lower trunk that flares out at ground level.  It is the transition area between the stem and the structural root system of a tree.

Tree root collars have evolved over eons to be exposed to air.  Buried root collars are detrimental for several reasons.  Cell respiration is disrupted, adding just one more stress to the tree.  This area of the tree can be intolerant to prolonged soil moisture, which can decompose tree bark and give way to stem pathogens.  Finally, buried root collars can lead to and disguise stem girdling roots.

Stem girdling roots arise in a few ways. When root collars are buried the tree reacts as if part of the root system has been damaged, and the tree forms a secondary root system.  These secondary roots can grow parallel to the stem, and begin girdling.  The other danger in this scenario, the secondary root system may take over water and nutrient uptake for the tree while the primary/structural roots slowly rot away.  Thus, a tree that looks perfectly healthy is standing with little to no structural root system.

Another way girdling roots develop on our landscape trees is through container production.  Many of the trees we plant are started in pots. When trees are allowed to stay in these pots for too long roots interact with the sides and begin circling the container. In many cases this is allowed to happen through every change in pot size, creating an almost hopeless structural root system.

With all that said, here are some pictures of messed up root collars and girdling roots:

Girdling roots around the circumference of the lower stem.

Large impacted girdling root, notice the diameter of the root compared to the diameter of the stem.

Severed girdling root, notice the large amount of stem damage that has occured.

What would you do for Liberty?

In 2010 an unknown assailant attempted to cut down a young tulip poplar in Charlotte's Freedom Park.  The vandal made it half way through the trunk before giving up.  While I know how many arborists feel about tulip poplars, this one was different.  This tree was grown from the seed of Maryland's original Liberty Tree.  You can read more about that story here: http://thequeenscrown.org/locations/6/Freedom-Park-Tulip-Poplar .

The Liberty Tree Tulip Poplar in the Summer of 2012

In an attempt to save the tree, horticulture staff installed guys in the direction of the damage and fastened steele plates adjacent to the cut.  Tulip poplars are fast growing trees, especially when young, and the idea was by stabilizing the trunk the tree will form reaction wood and grow over the damage.

After 2 years, see the amount of growth already put on by the tree.

Many of the prejudices we have about tulip poplars come from working on forest grown trees that suddenly find themselves in the middle of a suburban development.  Open grown tulip poplars can develop massive trunks with good taper, and are usually not as tall because reduced competition for light.  We think of tulip poplars as poor compartmentalizers, but the speed at which decay moves is relative, and may take decades to effect a tree that is today young and vigorous.

What would you do?  Would you have just removed it and said 'oh well.'  I think the horticulture department did the right thing, and because of these efforts we'll have an interesting tree to enjoy for years to come.

I'm Stubbed.

I've seen a rash of poorly pruned trees lately, and I think the picture below enforces why we should prune trees at the branch collar.  See the lower part of the branch forming callus tissue. This area is the remaining natural branch collar.

The rest of the cut is well outside of the collar, forming a stub.  You see how the tree has been unable to form reaction growth around this area.  This now leaves an entrance for pathogens, and may cause harm to the tree.  It also doesn't look very good.

Sometimes it isn't easy to get that final cut right, but its well worth your time.  Happy pruning out there.

Native Ash Trees: Oh No

I was at the ANSI IPM summit this week, and had the privilege to hear several industry leaders talk about the state of IPM. Dr. Mike Raupp from the University of Maryland was one of the speakers.  Dr. Raupp informed us the US stands to lose over 8 billion ash trees to emerald ash borer.

While this is tragic unto itself, something I hadn't thought of before was the effect on other species of plants and animals that have a symbiotic relationship with ash trees in the wild.  Untold numbers of animals use ash trees as primary food sources and shelter. In a greater view there are untold more animals that rely on the 1st bunch for food, seed dispersal, germination, etc.

So, what to do for these poor unfortunate creatures?  The Manchurian ash (Fraxinus mandshurica) has a natural resistance to emerald ash borer, and is similar to our native ashes.  Would it be possible to begin replanting our imperiled ash forests with Manchurian ash? If it is, could we save numerous species of plants and animals from possible extinction, assuming this Asian ash species would be a suitable substitute for our native ash?  Or would this exotic ash fall victim to a native pest our endemic ash has long since built resistance to?

These are interesting questions, and play a role in the future of our landscapes, forestry, and conservation arboriculture.

Manchurian ash, could you tell the difference.

The Scourge of Imidicloprid

If you're like me, then while your wife is looking at power tools at Home Depot, Lowes, or wherever, you are looking at the active ingredients on pesticides in the garden aisle.  Which means you have probably noticed that many general purpose over the counter insecticides are now imidacloporid based.

As an industry, we have relied on imidacloprid, Merit in its most popular form, for more than a decade.  Applied properly it is a great product.  It is in the neonicotinoid family of chemicals, and its mode of action is kind of neat.  The chemical interferes with an insects nervous system which results in death. Imidacloprid can be applied as a foliar spray, soil application, or directly injected into the trunk.  It is nontoxic to mammals, has a long residual, and can be quite effective.

However there are some things we need to consider when using this pesticide.  Studies have shown that with repeated use the molecule can make its way into the flowers of plants.  For trees and shrubs that are not wind pollinated this exposes pollinators to the product, and may lead to civilian casualties in the war against plant pests.

The other issue is pest resistance to imidacloprid.  In some areas imidacloprid has been so heavily used that it is no longer effective against targeted pests.  With imidaclolprid now being readily available to the public at large, and continued reliance on the chemical in many professional PHC programs, we may only assume that this pest tolerance will grow.

There are few 'silver bullets' in pest management.  Product/chemical diversity is an important part of an IPM program.  Imidacloprid may still be part of your chemical arsenal  but pest monitoring and investigating different products for use on target pests should be on the forefront.

The molecule

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