Category Archives: Shawns Tree Corner

Tree Benefits: Good Municipal Economics

Tree Benefits: Good Municipal Economics

In my line of work I come across tree lovers of all types and each has a unique reason for their arboreal passion. Sometimes its personal – they feel a positive aura around trees or they have family history rooted (pun intended) in an old oak on their property. And sometimes it is an awestruck appreciation of how trees open our eyes to the beauty of Mother Nature.

But you don’t have to be a tree lover to appreciate the value of trees. Many of us understand their importance from a practical view – shade keeps us cool, or a screen of Leyland cypress has saved our relationship with neighbors. My favorite practical reason? I like to breathe.

In recent decades science has provided us with even more practical reasons to appreciate trees. The USDA Forest Service’s Center for Urban Forest Research has compiled a good list of these ‘tree benefits’ and here is a sampling:
• One hundred trees remove 53 tons of carbon dioxide and 430 pounds of other pollutants per year, and they control storm water runoff by catching about 139,000 gallons of rainwater.
• Tree-filled neighborhoods lower levels of domestic violence and are safer and more sociable.
• In tree-lined commercial districts, shoppers stay longer, visit more often and spend more.
• Each large front yard tree adds 1 percent to the house sales price, and large specimen trees can add 10 percent to property value.

Such facts allow us to shift from a soft view of simply appreciating trees to attaching hard monetary values to trees and their functions. Armed with this new information many municipalities around the country are discovering that they can save a lot of GREEN by going green. What they have shown over and again is that while planting and maintaining public trees is not cheap, the economic benefits far outweigh this cost.

Generally speaking, for every dollar invested in tree infrastructure (this includes planting, maintenance, removal, sidewalk repair, arborist staff – everything) that municipality will receive 3 dollars’ worth of services that the tax payers would otherwise have to cover. A specific example cited by the Forest Service shows that one healthy 20 year old public tree costs about $36 per year in maintenance, but the benefits provided come to around $96. Extrapolate this to a realistic scenario and this means that one hundred public trees over 40 years provide $380,000 in benefits and only set the city back $148,000. That comes to a net benefit of $232,000.

It is clear why municipalities have shifted from seeing trees simply as ‘fringe benefits’ that only make it into the budget when there are surplus funds or are wrapped in as a small part of the public works department. To the contrary, cities and towns have learned that, in addition to creating a pleasant atmosphere, a tree canopy is an economic necessity that frees up taxpayer dollars for other essentials like education, police and road maintenance.

Phenology: When Trees Flower, And Much More

As spring unfurls we see tree phenology in action. What early bloomers are catching your attention? I saw (and smelled) a beautiful star magnolia in Shepherdstown yesterday. Red and silver maple flowers are popping all over the place. If any of you are DC commuters, then you may have seen magnolias, cherries, ornamental pears and perhaps early redbud and dogwood blooms. We have all of this natural artwork and more to look forward to here in the eastern panhandle in coming days.

Of course, phenology covers more than simply the joy of flowers. It encompasses all physical displays of growth and reproduction, and awareness of phenology provides us with more benefits than simple aesthetics. Here are just a few examples of the usefulness of knowing which trees are doing certain things at a certain time:

Stinko ginkgo control – If you live on a ginkgo block in DC with female trees as a part of the mix, you will be grateful that the Urban Forestry Administration waits until the flowers are just emerging before they begin their spraying programs. Otherwise there would be no effect.

EAB injections – Trees 101 is going to be treating ash trees for the emerald ash borer this spring and summer. The most effective insecticide is itself most effective when injected early during the tree’s active growing season. The vascular system is most active and transpiration is at its peak at this time. All the information suggests to me that mid-May is the right time this summer, but how can I really be sure?

Protecting bees – Even natural sprays to deal with tree/shrub pests can dramatically impact bee activity if applied while the target plant is in flower.

There are a few organizations that are taking advantage of the internet and ‘crowd sourcing’ phenology information from around the country. They ask volunteers to pay attention to trees that they regularly come across and enter any observed phenological events in their data base.  The result is a map that shows how the timing of these events varies across the country and how we see variation from year to year even in the same location. This information can be referred to for uses like those listed above, but perhaps more importantly it can, over time, inform us about the impact that climate change is having on our tree populations. Trees don’t have legs and cannot migrate to keep up with the warming trends we are experiencing. The implications of this fact are overwhelming but this kind of ‘crowd sourced’ phenology can at least provide some concrete observations of the phenomenon.

The Education Department at Casey Trees in DC is coordinating a District-based phenology project. They are the ones who got me thinking about this as a blog topic, actually. If interested, check them out at They are working through a larger effort conducted by the US National Phenology Network (, and there is another similar effort called Project BudBurst ( All of these groups emphasize the value of the data AS WELL AS the value of the stewardship and education that is nurtured through keeping a close eye on your tree population. Will you be the first to log the flowering of paw paws along the Potomac? Have fun!

Trees 101 hosts Tree Nurturing and Pruning Workshop

Shawn of Trees 101 (along with his lovely partner in pruning, Linda) hosted a great bunch of tree lovers during the first annual Potomac Valley Audubon Society Tree Nurturing Workshop this past Sunday. We spent almost three hours at Morgan’s Grove Park in Shepherdstown (Jefferson County, West Virginia) discussing the fundamentals of pruning for health and structure, and the essential aspects of ‘cultural care’ of trees. It was cold for late March but we warmed things up by putting our knowledge into practice! We didn’t hold back as we tackled DOMINANCE, CO-DOMINANCE and SUBORDINATION. Yes!
Here is a link to the US Forest Service’s guide to pruning. I have made a customized handout as well. Email me if you want a copy! (

Spring Tree Care

Tree Thoughts: Anticipating Spring

Well, the equinox is on Thursday and they say that spring is actually going to come. So with that in mind, I thought I’d mention a few spring tree care thoughts to keep in mind for the upcoming longer, warmer days.

Planting: The ground has thawed but the trees are mostly dormant. Now is a good time for tree planting. If you want to consult about native options for your landscape, I strongly recommend contacting Virginia Winston of Winston Gardens (; 304-267-6924). Remember that newly planted trees can suffer drought stress anytime it is over 40 degrees with no precipitation for two weeks. Make sure you have a watering plan before you get those trees in the ground!

Fungi: They are going to get busy out there. If you have trees in your landscape that are particularly susceptible to fungal/bacterial disease (needle cast of blue spruce, cedar-apple rust on serviceberry/other rose family members, anthracnose on dogwood, just a few examples) or if they have shown symptoms over past years, the first thing to remember is to maintain sanitation. Make sure last year’s leaves/needles on the ground or stuck in the tree are removed from the site. Fungal spores can overwinter on this debris and the splashes of spring rain can let them loose to start the disease cycle. Next you might want to consider neem oil or fungicidal sprays over the course of active flowering and leaf out. Timing is key and varies by species and weather conditions.

Pruning: If you maintain clean, sharp tools and make proper pruning cuts, it is ok to prune in early spring. However, it is always wise to avoid pruning during wet weather. Maples and others will ooze sap but that is mostly a cosmetic issue. Certain trees will be more susceptible to certain pests when pruned during the growing season (e.g. elms susceptible to Dutch elm’s disease) and through the summer, so if you are in doubt wait until next winter if you can.

Mulch: If mulch is a part of your spring sprucing up plan, consider working in some leaf compost along with your typical product by spreading a thin layer underneath. This is a great soil conditioner that breaks down faster and contributes that organic matter cycling you want in a tree’s root zone. LeafGro is available in bags at Home Depot, Potomac Farms and other area stores. No matter what you use, make sure your mulch is no more than 3 inches deep and no mulch should be touching the bark of the tree.

Fighting Emerald Ash Borer: The EAB phenomenon is wiping out all ashes in the area that are not treated with insecticides. Small healthy trees can be treated with a preventative product available to homeowners. Trees above 10” diameter, though, will require an industrial product, especially considering the heavy infestation we are experiencing. Treatments are most effective during the ash tree’s active growth period so it is best to address this issue before the end of June. Of course there are always implications to introducing insecticides to an ecosystem, so it is a matter of finding that balance that you are comfortable with. Trees 101 is offering systemically injected treatments that limit the environmental impact and will only need to be repeated every 2-3 years. To learn more about EAB, check out this multi-agency website:

Enjoy the vernal gifts from Ma Nature!


Trees and extreme cold and heat

How do trees survive this freezing weather? Are they just super tough or do they have anti-freeze in their veins? Here is a Phytophactor article with good information on this remarkable adaptation. It suggests that there may be a little bit of both going on out there.

There are other questions that arise when talking about trees and weather that take the discussion in a different direction. Questions such as: How are trees going to survive our overall warming trends resulting from climate change? Should we be planting warmer weather species in anticipation of the changes?

There is no clear consensus on this but what I can comment on is the fact that some urban forest managers have modified their tree planting lists to accommodate for trends that they and scientist observe and anticipate. In Washington DC, for instance, it was common to include sugar maples among the street trees to be planted, but the arborists there have dramatically cut down on this particular species. There are certain locations with suitable microclimates where sugar maple might be a good choice, but in typical DC planting locations there are better options.

I have also read that the City of Chicago has removed the white oak from its planting list for similar reasons. It is a marginal species as is and the anticipated warming makes it too risky. Current conditions may allow a newly planted white oak to survive its initial transplanting and even a few summers that follow, however by the time it matures and begins to provide its ecological benefits the urban environment is likely to be too harsh.

Many say planting warm weather species may be jumping the gun a little bit. Damage caused by harsh winters may counter-balance the benefits of a species’ heat tolerance. For now I recommend maintaining a diverse pallet and consider eliminating certain species that are proving to be problematic with summer heat and drought stress. And always remember that despite overall trends conditions can be highly variable from location to location. Consider the micro-climate and soil environment where you intend to plant and think “Right Tree, Right Place, for the Right Reason.”

Shawn’s EAB article in The Journal newspaper

Shawn of Trees 101 has had an article published in The Journal newspaper that covers West Virginia’s eastern panhandle. Topic: Emerald Ash Borer and what we can do about it! Same article is likely to be in the local Chronicle, Observer and Spirit of Jefferson as well. This is the basic contents:

All Eastern Panhandle Ash Trees at Risk

We imported a fungal blight that killed off the American chestnut in the early 1900s. Now we are seeing a wave of death among our ash species caused by another imported pest, the emerald ash borer. EAB was first discovered in Michigan in 2002 and today the beetle has spread to 22 central and eastern states where its larvae feed on the inner bark of ash trees and kill them in as little as 2 to 3 years.

Unfortunately, yes, West Virginia is on that list of states and the impact is already being felt in the eastern panhandle. It is impossible not to notice entire ash stands wiped out at Cacapon State Park and further devastation throughout Morgan County. And while a walk through Altona Marsh near Charles Town is a thrill for birders, the experience is dampened by the site of scores of ash trees succumbing to EAB. The experts cannot tell us yet if the nation’s entire ash population will be eliminated but there is no doubt that all ashes in our region are at risk. Tens of millions of ashes have succumbed to the fate of EAB so far and the pest shows no signs of slowing down.

Area forest managers have been aggressively harvesting ashes while they still have utility or timber value, but other than that there are very few proactive options for coping with EAB on a large scale. However, THERE ARE OPTIONS for small scale management. Individual trees can be protected with insecticides injected or otherwise introduced into the tree’s vascular system. When done properly this approach has proven highly effective. The treatment is relatively safe (there is even an effective organic product available) as the insecticide stays isolated within the tree. Plus the cost is negligible when compared to both the value of the tree and the costs associated with managing a hazard tree that will require removal by a tree service. Some homeowners have had success with preventative measures on young (less than 10 inches in diameter) EAB-free trees by using insecticides available to the general public. Most trees, though, require treatment by a professional, especially if there is the possibility of an existing infestation.

In Martinsburg a recent tree inventory revealed that ash trees make up more than 10% of the street tree population, providing thousands of dollars of ecosystem services for the city each year. Morgan’s Grove Park in Shepherdstown is populated with stately ash trees and West Virginia’s third largest green ash is a part of that population. It is not too late to act to protect these trees. Of course, Berkeley and Jefferson Counties have budget limitations that may make proactive treatment unaffordable. Unfortunately this means we will have no choice but to pay a far greater cost for removals when these trees become standing dead hazards. Setting the cost of public risk management aside, if we consider the historic character these mature trees add, plus the cooling, air filtering, water cleaning benefits they provide our community, can we truly afford not to act?

Treatments are most effective when performed before the end of June. If you have ash trees to protect now is the time to figure out a proactive strategy – a wait and see approach simply will not work. Visit this multi-agency public website for the latest information:

Shawn Walker is a consulting arborist based in Shepherdstown. Learn more about Shawn and Trees 101 at