Friday Photo Feature - February 11, 2011

Growing pile of pruned branches at Casey Trees HQ.

Our tree planting crew is doing a lot of pruning this winter as a part of our tree care efforts, so here is a photo of the growing mound of pruned branches. We'll keep you posted as it grows!

Friday Photo Feature - February 4, 2011

Street trees in Brookland.

Can My Tree Be Fixed?

Contributing Writer - Mike Galvin, Deputy Director

In our prior post, we discussed how to inspect trees for damage following a storm. Today we will discuss the question "what types of damage can be fixed and what types cannot?"

Uprooting is very difficult to fix for any but the youngest trees. As the size and age of the uprooted tree increases, so do two other factors: the cost of the repair and the likelihood that the repair will not be successful.

Stems are assessed on the type of defect, the size of the defect, and what type of conditions you expect the tree to withstand. Hollow trees are common, and as long as the trunk is no more than two thirds hollow, that is not a concern under normal conditions.

Limbs are assessed as stems are. In addition, the closer a side branch is in width to the branch it is growing out from, the greater the likelihood that the limb will break off (these are called co-dominant limbs; stems can also be co-dominant if a tree is multi-stemmed). Limbs that have lost 50% or more in a storm are candidates for removal.

 

The hazard zone can be described in many ways depending on where on the tree the defect is, but the simplest way to describe it is to walk as far away from the tree as the tree is tall, and to “draw” a circle around the tree this way and then look at what falls within the circle. Is it your house? A street? These items are considered “targets”.  A target is generally a person or piece of property that would get damaged or hurt if the tree or part of the tree fell.

All treatments can be boiled down to three options:

1. Remove the risk by removing potential targets (move any potential targets such as people and property out of the hazard zone).
2. Mitigate the risk by repairing the damage by pruning, cabling, etc.
3. Remove the risk by removing the tree.

In urban settings, the first option is often off the table due to site constraints. This means you can either prune or remove the tree, depending on the extent of the damage. Again, if you need these services, we recommend you contact a professional Certified Arborist for help. If you have to remove your tree Casey Trees has a number of programs that may help you with a replacement tree.

Tree of the Month: American Sycamore

Peeling sycamore bark.

Some deciduous trees have a distinctive appearance in the winter, even without their leaves. The American sycamore (Platanus occidentalis) is one of these trees. Several trees are commonly called sycamores, but the native American sycamore (also known as the American plane tree, occidental plane tree or buttonwood) is a prominent tree in the forests and waterways of the eastern United States.

The sycamore stands out with its interesting bark, which separates into scaly plates that create a multicolored, mottled texture. The bark peels off, uncovering new white, brown, gray and green layers underneath. All trees with bark go through a process similar to this, but the sycamore shows off its transformation as it grows. Another interesting feature of the tree in the winter is its large round fruit which hang on long stalks. These fruit are prominent throughout winter; they break up and disperse their seeds in the spring.

American sycamore leaves and fruits.
Photo credit: Allen Bridgman, South Carolina
Dept. of National Resources, bugwood.org

The sycamore's twigs branch out in a zigzag formation, with buds formed at each angle. Its broad palmate leaves have three or five pointed lobes with teeth lining the margins. The tree can be found in river and stream areas, particularly along the Anacostia and Potomac Rivers and the C&O Canal. Casey Trees planted them along the Anacostia in 2006 in Wards 7 and 8. There is also a notable sycamore in the park at Franklin Square.

Sycamore at Franklin Square's northwest corner
at a Casey Trees Citizen Forester training.

Facts about the American sycamore:

• A close relative, the London planetree is more commonly found as a street tree in DC because it is more resistant to soil compaction and pollution. The London plane (Platanus x acerifolia) is a cross of the oriental plane and the American sycamore.
• Although it doesn't often have the chance to do so in a dense city, the sycamore can grow to be quite massive -- more than 100 feet tall and very wide.

Use our interactive map to see where we have planted American sycamores. Search for "sycamore" under the category Casey Trees' Plantings. Casey Trees has planted 30 sycamores and we have planted more than 250 of its hardier relative, the London planetree.

Is My Tree Damaged?

Contributing Writer - Mike Galvin, Deputy Director

As we are in the midst of another stormy winter, we wanted to share some information on trees and storms. This first of a two part series will help you answer the question: is my tree damaged? A subsequent post will help you answer the question: if so, what can I do about it?

In The Body Language of Trees, a handbook for failure analysis, Claus Mattheck and Helge Breloer set out a process for performing Visual Tree Assessment (VTA). The 3-step VTA method should be used to confirm the presence of a defect. If a defect is found, it should be further investigated.

Mattheck and Breloer propose that we can inspect a tree for defects by reading its body language. Trees grow in ways that make sense. The roots provide stability and water and nutrient uptake. The crown (leaves) provides leaf surface, and so represents food-generating potential through photosynthesis. The stem connects the top and the bottom, providing connectivity and support. Trees grow according to the Axiom of Constant Stress, which states that an optimal structure has a uniform stress over the whole of its surface. So trees invest material to reduce mechanical stress. If you see something that does not look normal it is a cue to further investigation.

Walk 360 degrees around the tree of at all possible. Look at the roots, then the trunk, then the crown. Be careful! There may be damaged or hanging limbs in the crown – they could cause injury if they fall. Some common types of failure associated with storms are uprooting, stem failure, and limb failure.

If the tree is leaning and there is a soil mound or exposed roots on one side of the tree, it could indicate that the root system is failing. Indicators of potential stem failure include cracks, bulges, cavities, and bent stems that do not return to vertical after snow or ice loading. Limb failure indicators are similar to those for stems.

So walk all the way around your tree and inspect it from roots to crown. If you see something that doesn’t look “normal” (a crack, break, lean, etc.) it is a flag that something may be wrong. In such cases, we recommend that you hire a Certified Arborist to inspect and treat your tree to minimize risk.

On Thursday, we will discuss which types of damage can be fixed and which types cannot.