Circled Roots

I spend the majority of my time examining trees. And I really like that! However lately I have been noticing more and more trees with circled or girdling roots. The outward expression of this condition can be very obvious, a large root or group of roots circling a tree above the surface of the soil quite clearly strangling the life out of the tree above. Or it can be practically un-noticeable, a buried root that circles around below the soil level choking the life out of a seemingly healthy tree. And the signs can also include thinning tree crown and eventually die back. Trees generally have a pronounced widening at the point where they enter the ground, called the basal flare. The tissue at the base of the tree is a mixture of trunk tissue and root tissue that is very tough and resistant to insects and decay. If you have ever burned piece of a stump it takes forever. If you have tried to chop a stump out with an axe you will know how tough this tissue is. In fact one of the most common ways to remove a stump is to grind it out like you would grind a rock.

Root tissue is different from this transitional trunk flare tissue and will not join or graft to it when they come in contact. When the root tissue tries to grow over the trunk tissue, the tissues continue to expand compressing the trunk tissue. The phloem in the trunk tissue, the outermost layer of living cells is responsible for transporting sugars back down to the roots from the leaves where it if produced. The phloem becomes blocked and compressed by the root pressing against it and results in further swelling above the blockage. This continues until the tree completely blocks itself or the root is removed.

This past weekend I purchased a Japanese black pine on a standard, while I was planting it I discovered several girdling roots. Fortunately they were small and I was able to remove them with a pair of pruners while I was planting it.

The lesson learned is that even small trees can have potentially large problems. You must carefully examine their roots and take corrective actions. Roots should move away from the trunk in a pattern resembling the spokes of a wheel. If they circle back or cross other roots sideways to the trunk, problems may be looming.

Three seasons ago we were able to identify a potentially fatal root conflict on a Dawn redwood. We were able to excavate the root collar with high pressure air and carefully remove the root. Typically the results are slow to show, however this particular redwood made such a remarkable recovery, you can barely see where the root was circling the trunk. If appropriate timely action is taken the problem can be averted and the trees life extended.

If you have trees with troubled roots contact your ISA Certified Arborist to develop a root recovery plan.

Root Grafts and Dutch Elm Disease

This isn’t the first or the last article written on Dutch elm disease. Tragedy strikes when I see a formerly healthy elm tree stricken by this typically fatal disease. The horror scene, leaves turning yellow and brown and clinging tenaciously to its expired vase like form.

Dutch elm disease is a fatal vascular disease that infects and kills North American Elm trees. This fungal disease Ophiostomata Ulmi is spread from tree to tree by Elm bark beetles. The disease travels long distances by bark beetles living and breeding in Elm fire wood.

For many years I would mark one or more trees for removal in this one shelter belt of trees in my survey area. The City would come quickly and remove the tree to prevent the spread of DED to the next tree in the row. The following year we would come out and the next tree in the row would be showing signs of a late season infection. These typically are small stunted leaves that emerge, turn brown and die quickly. This differs from the more typical late season infection where a healthy normal tree has a branch or two that suddenly turn yellow and brown. Some leaves drop but many are left With hanging on the branch. This symptom is called “flagging”. Late season infections trees sickly and stunted die early in the season.

Late season infections are typically caused by overwintering elm bark beetles spreading the disease spores as they burrow into the trees bark. This direct injection of Dutch elm disease directly into the vascular system of the tree overwhelms the tree causing death the following spring.

The row of trees was being treated successfully year after year to reduce the population of overwintering elm bark beetles and no other trees in the row were affected, just adjacent trees.

The only possible way for the trees to become consistently infected was through root grafts. Root grafts occur between trees, typically of the same species, where the roots come in contact with each other and physically bond. Trees pass fluids, like sap, electrical signals and bio-chemicals between them through these grafts. Unfortunately root grafts also allow diseases like Dutch elm disease to pass between trees. Once you take the diseased tree down the sap flows back through the roots and into the next living tree grafted to the infected tree that was removed.

We finally broke the chain of infection by taking down the infected tree and the next two uninfected trees in the tree row. The next year the remaining trees were uninfected and remain alive to this day. Roots can also be root pruned and separated using a deep plow, trencher or ideally by excavating with high pressure air. If you have elm trees on your property contact your ISA Certified Arborist to develop a disease management plan.

Tree Fertilization

The topic of tree fertilization can be a controversial one. I personally have been on both sides of the fence on this debate which tends to have two primary views. One view is , “Trees do well in the woods and fertilization in your yard isn't needed”. The other view is that, “Trees in their natural environment recycle nutrients and your yard the soils and nutrient recycling are far from ideal”. The first view is one that I held before I spent many years studying trees and their responses to supplemental fertilization. I have developed an understanding for the second position after years of careful observation.

Your yard is a harsh place for trees, the soil has been compacted and modified to such an extent that it no longer bears much resemblance to the loamy duff of the forest floor. Forests are harsh environments, but they are places that trees are uniquely adapted to survive and thrive in. Trees exist in communities and grouping that balance nutrient requirements. Unseen battles for scarce nutrients take place in the forest and result in the forest you are looking at. The trees in your yard certainly would not exist as a community naturally in the woods. I no longer think fertilization is “ Snake Oil”. When correctly prescribed, formulated and correctly applied it is one of the most beneficial applications you can make to your trees.

The results of fertilization can only be seen over time in the growth and development of your landscape trees. Any gardener knows that to keep a plant alive you must water and fertilize it as needed and on a regular basis. If you don't they simply struggle and fade away. The basic N-P-K of fertilizer, nitrogen, phosphorous and potassium, come in a variety of formulations and forms. For trees it is important to have a substantial proportion of the nitrogen in a slow release form that is available to the tree on an extended basis.

There are a variety of ways to apply tree fertilization, broadcasting on the surface, drilling and placing granules into the soil, tree spikes, low pressure high volume hose end feeders, and high pressure liquid injection systems. Each has its advantages and disadvantages, having used all of them over the years I do recommend high pressure liquid injection as my method of choice. This method has the advantage of being able to quickly and accurately, both important considerations, deliver the correct blended fertilizer and soil amendments to the root zone. As we have discussed many times in the past most tree roots are in the upper 12 inches of the soil where oxygen and water are available. Soil fertility, micro nutrients,soil pH and root stimulation are only a few of the areas that can be addressed using the correctly formulated soil injection. The important issues of formulation, timing and proper application can be prescribed by an ISA Certified Arborist. If you want your trees to thrive and prosper, contact your ISA Certified Arborist.

The Depths of Planting

Root Flare on Tree Planted At Right Depth

This time of year will always find me answering questions at plant sales or speaking with students about the importance of planting trees. Unfortunately this year an unseasonal cold prevented me from speaking at either. I did manage to attend and was able to confirm the old saying that “ you have two ears and one mouth so listen twice as often as you speak”. While my voice was out of commission I was able to stand back take a few pictures and listen to one of my fellow arborists speaking with a group of 4 and 5 year olds. He, being unprepared due to my sudden laryngitis , showed true mastery in arboriculture by improvising a great presentation on trees, how important and present they are in our lives. Halfway through I croaked “ Whats in the bag?” and he pulled a small white spruce plug out of the paper bag he was holding. The children were ecstatic and without missing a beat he held the tree up side down and asked “ Do we plant a tree like this” to a gang shout reply of “ No” they all replied, flipping the tree. “ How about like this?”,the tree was now right side up and all agreed that “Green on Top” was the way to plant. So how do we go from this simple consensus to over half the trees in the average landscape being planted to deep?

The simple truth is if I you walked out your door and found a planted tree it would more than likely be planted too deep. At the mall,shopping center, park or many of my clients properties there are no shortage of these buried alive trees.

Trees grown in nature from seed are rarely planted to deep. Flooding, landslides and wind sedimentation can cause tree burial but it's rare. In our landscapes the most common culprit is planting too deep and settling after planting.

Trees almost universally flare out where the roots differentiate from the trunk tissues.

This basal flare should be your clue to correct planting depth. The flare should never be completely buried and should generally be at the surface or just slightly above. This translates to a centimeter or half inch or less above the surface of the soil. If you see a tree that looks like a pencil coming out of the ground, strait with no flare at the base it is likely planted too deep. Trees want to grow roots in a downward direction, this is called geotropism and ensures roots remain in the ground and not heading to the sky.

The process of planting a a tree or shrub often starts with a hole in the ground that is more suitable for a fence post or pit barbecue than a plant. Trees do best if planted in shallow lens like planting sites that are wider than deep. Care must be taken in most soils not to glaze the outer edge of the planting site by packing it while shoveling. Once you are done take the side of the shovel and break up the hard polished soil so the roots can easily penetrate it. If the tree requires staking once planted do so loosely and be sure to have a plan in place to come back and remove the stakes and wires once the plant has settled. If in doubt when planting trees contact your ISA Certified Arborist they are the go-to experts on tree planting and care.

Too Mulch of a Good Thing

Mulch was touted as the cure for all things soil related when it first introduced in the early eighty's and has been used with much success and notable failures since. Research is currently underway to see if our current mulching practices are of benefit. To understand how mulch benefits trees we must have a few basic facts about the soil it protects.

Mulch is a protective cover for soil. Soil is an environment that contains solids, gases and liquids. As long as they are in the right proportions they work in conjunction to create the ideal habitat for roots. If they are out of proportion or not present at all they exclude roots and prevent plant growth. Too many solids and soil becomes compacted and roots can't get enough oxygen and die failing to penetrate the soil. If you have roots coming to the surface of your lawn this is the problem. If you have a high water table there isn't enough oxygen in the soil roots will be excluded. Too little water in the soil and trees and plants will dry up. If the temperatures in your soil swing wildly from hot to cold many plants will suffer root injury and possibly die.

Trees growing in the forest develop their own natural layer of mulch called “duff” this consists of many years of decaying leaves and debris that falls from the trees forming a rich insulating mat on the forest floor. The forest duff reaches a state of equilibrium decaying at a rate that prevents it from suffocating the trees that produce it.

Mulch often isn't made from the same types of trees that are being mulched. Some mulch, coming from trees that don't decay readily, like cedar mulch, can build up. Mulches made of dense materials like shredded leaves can prevent air infiltration and must be used sparingly. If mulch becomes saturated with moisture and prevents air infiltration roots will migrate in to the mulch and cause growth problems. Roots that grow into mulch will often circle the tree eventually girdling and strangling the tree. The problem is made worse by trees that are planted too deep or in pits. They are trying to grow roots out of the hole they are buried in.

Proper mulching is an ongoing process and requires inspection and occasional maintenance. You really can't just keep adding it year after year and expect it not to have negative effects. Recent innovations in mulch delivery, namely blowing it into place have made this “ Mulch Glacier Effect” a more common eventuality. To explain, if the mulch is being deposited faster than it is decomposing it builds up into a mulch glacier and starts to move down slope! It also piles up around the trunk of the tree and starts it to decompose. Trees are made of wood, a surprise to many, and placing wet wood against it causes it to decay.

Photos S. Smith

I have included two pictures that show soil profiles before and several years after a deep layer of mulch was placed on a compacted turf area. Notice the change in color and the development of rich organic loam horizons deep below the surface.

I'm still a fan of mulch applied right. Contact your ISA Certified Arborist to see if your mulch is correctly applied.