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by Steve Turner

Sudden oak death is as bad as it sounds. It is a disease caused by a strain of a common fungus that will often only cause minor leaf blotches on other types of plants. When introduced to oaks, however, it will cause a very quick demise of the tree. Bleeding cankers that ooze a black, resin-like substance are the calling card of this disease. The tree dies shortly thereafter.

The good news is that it has yet to be found in Michigan. So far it has been confined to the West Coast, mainly northern California and the Pacific Northwest. The bad news is that those are areas that ship many plants to the Midwest.

The odds of this disease coming here on an alternative host and then infecting our native oaks is pretty high, judging by the spread of these types of problems in the past. I’m afraid it is more of a question of when, not if, it will get here. Only by asking for and buying only Midwestern-grown stock can we help reduce the chance that this (and other invasive organisms) ends up here in the long run. At this time there is no known cure for this disease.

Next is oak wilt, also caused by a fungus. It blocks the vascular system of the trees, causing them to wilt and die, very similar to Dutch elm disease (DED). Just like DED, it is spread by an insect and by root grafts. The good news is that the picnic beetle that helps spread the fungus is not as proficient as the bark beetles that spread DED. So, following simple cultural practices, such as never pruning oaks during the growing season, and promptly repairing and sealing any wounds caused by storm damage can greatly reduce the odds of trees being infected.

However, if your neighbors or utility companies don’t follow these same guidelines and nearby trees become infected, then oak wilt can spread through root grafts to your trees. As mentioned earlier, only white oaks can be cured if they become infected. In red oaks, you can only treat as a preventative measure and just like DED, they are still vulnerable to root grafts whether they are treated or not.

The only way to prevent infection through root grafts is to trench and sever the root systems between healthy and infected trees. If you have red oaks in areas where there are known infestations and they are important landscape trees, it would be wise to take a preventative approach.

Anthracnose is a foliar disease that causes browning of leaves from the veins outward, not to be confused with leaf scorch, which causes a similar effect, but from the edges inward. Anthracnose infects trees in the spring and the damage will appear during the growing season. It seems to infect white oaks much worse than red oaks.

Severely damaged leaves will generally fall off, leaving the tree looking sparse. Often the tree will try to put out new leaves to replace the damaged ones. If the tree has been infected for several years, it has a more difficult time finding the extra energy to do so year after year.

This is the point at which a normally mild disease can start to threaten the health of these trees by weakening them enough so that other organisms such as chestnut borers can enter the tree and cause their demise. Severely infected trees can either be injected in the fall or sprayed in the spring to help control this disease.

Late season frosts are not a disease, but they can cause disease-like problems for white oaks, which tend to leaf out a little later than red oaks, making the young leaves more vulnerable to the freezing temperatures. Generally the leaves will turn black and drop off or become distorted, with dead areas surrounded by healthy ones. If it happens often enough, it can lead to the same results as anthracnose, causing the tree to weaken over the years.

Iron chlorosis (iron deficiency) is also not a disease but an environmental condition that is very common in red oaks, especially pin oaks. It is not caused by lack of iron in the soil, but by the pH of the soil being too alkaline, causing the iron to be bound up in the soil and unavailable for the tree roots to absorb.

There are several ways to address this problem. A short-term solution is a trunk injection of iron to supplement what the tree cannot get on its own. This will only last 1 to 3 years depending on the situation.

More permanent solutions include: 1) adding chelated iron to the soil; this is a special kind of iron that will allow the tree to absorb it regardless of the pH, or 2) replacing soil around the tree by blowing out the high pH soil with a special tool and replacing it with better, more acidic soil, similar to replacing the soil of an ailing houseplant. This method will last many years, but is not always feasible in all situations (if access to the root zone is limited by structures or pavement). Left untreated, a tree will slowly starve to death over many years as photosynthesis is reduced by the lack of iron.

So, if you have an ailing oak, it would be wise to have it checked out sooner rather than later to determine what might be affecting it and to select the best course of action to help it recover. We owe it to these magnificent trees that have served mankind so well for thousands of years and helped shape our evolution.

Steve Turner is a Certified Arborist from Arboricultural Services in Oakland County, Michigan.

by Steve Turner

Oak trees are so common around us that we often take them for granted. The importance of these hulking giants that provide shade and numerous resources that we depend on in everyday life are often overlooked. There is not one other species of tree that mankind has been so dependent upon as the mighty oak.

In fact, it could be argued that if not for the oak, life as we now know it might be very different. How is that you ask? First, we would have no written history or early works of literature to appreciate because until ink was made from the galls of oak leaves, it would simply fade away in a few years, never to be seen again.

Second, we might all be back in our native lands because the wood from oaks was the only wood capable of building a ship that would be strong enough, yet flexible enough to cross the oceans. The Sistine Chapel and many of the other great architectural wonders of Europe would not exist if not for their frames made of oak.

Leather coats and shoes, as well as the leather seats in the cars we drive would not exist if not for the tannins in oak bark used to turn animal hides into leather. And don’t forget wine or spirits, which are dependent on the white oak barrels in which they ferment and age before being bottled.

For over 12 millennia, man was dependent on wood for his survival. Only for the past 250 years or so did that dependence shift to oil and coal, and we can already see the end of that era coming.

The next time you meet a person named Cash or Cooper, you can smile and know that if not for oak, they might not have a name. The first was named after oak and the second for what they made out of it. Many common names have derived from trees, such as Smith or Johnson, but none more than oak; it is the most common tree name in all of western language. Even in early civilizations like the Druids and Celtics, names were derived from oak. Some will even argue that Stonehenge is built very similar to the ray cell pattern in oaks.

It is not a coincidence that if you look at a map of early civilizations, they grew out of the shade of oak trees. It did not matter if they were in Asia, Europe or the Americas, they all shared one common tree. This might be the reason that acorns were a staple of all their diets and they were dependent upon them for survival.

Oaks are very unique in their adaptability skills. It is believed that they originated out of the Mediterranean first as evergreens. Later, after the Ice Ages, they were able to fill gaps that other trees could not, and their ability to adapt and change allowed them to become the dominant species throughout the world. Oaks are the only species of trees that have both deciduous and evergreen types. They are native to every continent but Australia and grow from the northern edges of the tropics to the southern edges of the northern tundras, like a band around the middle of the Earth, a feat no other tree species can boast.

All this from a species that is neither the biggest, oldest, strongest and definitely not the fastest-growing—so why is it so dominant? How can it be called “the king of trees” when it holds none of these distinctions? Simple—because of its ability to adapt to the environment around it.

A good example is our urban forest. Look around. What are the majority of the really big trees around us? Oaks. Why? Because they have adapted to our urban environment. When developers build around trees, the beech and the cherry are the first to die. They cannot stand the disruption to their roots. Next are the ashes, elms and maples—they hang on longer but are not as strong as the oaks and are more vulnerable to wind damage when the forest is thinned. Disease and insects have also increased the decline of some of these trees, but not the oak. It continues to be the staple tree of our urban forests, able to outlast and out-compete all its competition to remain the king.

Nevertheless, the king is in trouble. Pressure from new developments, people expanding their homes in older neighborhoods with mature trees, and trees running out of room for their roots to grow due to sidewalks, driveways and buildings are all beginning to take a toll on these trees. I am seeing more and more dead or diseased oaks than I ever have before. I fear we might be looking at some serious problems if these trees are not taken care of. To read about common concerns with oaks and what can be done to help them, click here.

Steve Turner is a Certified Arborist from Arboricultural Services in Oakland County, Michigan.

Author’s note: Thanks to William Logan, author of Oak: The Frame of Civilization, from which much of the factual information for this column was obtained.

by Steve Turner

You are ready to start your new landscape project—you have done the planning, researched your plants, and even had a soil test performed to help you make better choices in your plant selection. Your soil test will tell you 4 important things: the type of soil you have (sand, silt or clay), the pH of the soil, what nutrients are present and in what amounts, and the nutrient-holding capacity of the soil.

So now you are ready to begin, right? Well, that depends. Would you buy a house based upon just 4 facts, like size, location, age and style? Or would you want to know a little more, such as condition, extra features, color, floor plan, etc? While the 4 main facts are very important, it is often the other factors that will help determine your decision and your level of satisfaction in the end.

Knowledge equals success in most cases and your soil is no different. The first thing is to know whether you have dirt or soil. Dirt is what’s left after developers scrape off all the good stuff, while soil is alive and is a living, breathing network of millions of organisms working together in their environment.

There are six major types of soil organisms: nematodes, bacteria, fungi, protozoa, earthworms, and arthropods. What types, how many, and in what ratios will tell you how healthy your soil is and what types of plants will grow best in those conditions.

The first test you need to do is simply take a shovel and turn some soil over and look at it. Is there anything moving or any signs of life? Is there organic matter present? How hard was it to dig? Did you have to jump on the shovel or did it go right in? If you can’t answer yes to any of these questions, or you couldn’t even get the shovel in the ground, you have dirt. You need to create soil first, before you plant, to avoid future problems.

Just like us, soil organisms need three things: air, water and food. Build these into your soil, and the organisms will come. Tilling your soil and adding organic matter will accomplish all three at once. You will create more space for air and water, and add food to feed the organisms that make up a healthy soil.

This is a must in new subdivisions. Homeowners should request that landscapers amend the soil by tilling in compost and pay the extra costs to do so, instead of spreading a couple of inches of topsoil on top. They would save themselves money in the long run by avoiding extra water, fertilizer, and pesticides needed to keep a broken soil system running. Add in dead plants, replacements and the wasted time dealing with all of the above and it really starts to add up.

If you have soil without compaction and you have organic matter, but not a lot of soil organisms present, you can increase their numbers by first eliminating pesticides and excessive synthetic fertilizers on the landscape. In their place, use manure, kelp, or fish-based fertilizers, and continue to add organic matter to feed the soil organisms, which, in turn, will feed the plants. The interactions of all these soil organisms are critical to a healthy system and by manipulating the ratios of one or another, can dictate what types of plants will grow best in a particular environment.

The three major types of soil environments are fungi-dominated, bacteria-dominated, or an equal ratio of both. Trees, shrubs and woodland plants do best in fungi-dominated soils, lawns and prairie plants in bacteria-dominated soils, and agricultural plants in a balanced soil.

There are both good and bad types of all these organisms. Some nematodes feed on plants, fungi, bacteria, and even other nematodes. Some fungi feed on plants, nematodes, bacteria, and protozoa. And so on. In a healthy soil, the beneficial organisms will keep the parasitic organisms in check. The key to this is keeping the soil aerated. Compacted or saturated soils with little air cause anaerobic conditions in which the parasitic organisms thrive and the benificials die. If the soil has a foul smell, it is anaerobic.

Give thanks for soil decomposers such as earthworms, sow bugs, centipedes, etc. They are constantly aerating the soil, as they transport organic matter on the surface down into the soil. There, the other soil organisms can further break it down to forms that the roots of plants can absorb. They are the workhorses of the soil and have been tilling the soil long before the plow was invented.

The use of insecticides, fungicides and nemacides kills both the problem organisms and the beneficials, and is often only a temporary solution. This throws the soil out of balance and can create more problems that require more treatments. There are many alternatives available today that work with the natural system to correct the problem. Some examples are nematodes that feed on other nematodes, fungi that attack grubs and fungi that will kill other fungi for many lawn diseases. Often one application of these will last several years in the soil and avoid the need to constantly retreat a problem on a yearly basis.

All in all, after you understand the soil’s natural system, it is often easier to work with it than against it. Familiarizing yourself with it can save you time and money in the long run.

Steve Turner is a Certified Arborist from Arboricultural Services in Oakland County, Michigan.

by Steve Turner

Trees provide us so many benefits it would be hard to place a true dollar value on their worth. They provide shade, beauty and clean the air we breathe. Essentially as a group they help support life on earth. But how much is one tree worth and how do you figure it out? A tree’s monetary value in a landscape is measured by the cost of replacement, unlike a tree in a forest that is measured by its timber value.

Many factors go into appraising a landscape tree, including size, age, location, health, structure, and species. Each category is judged by its level of importance and a score is given in each. A formula is used to then determine a cash value of the tree’s replacement.

Obviously size and age are going to be very important factors because we use the cost of the largest tree we can plant and then start multiplying it until we get to the size of your tree. So take a tree that has a circumference of 100 inches, and the largest replacement tree is only 10 inches and costs a thousand dollars. If all the other factors are good, the value could be up to $10,000 for replacement. Slow-growing trees are going to be worth more than fast-growing trees of similar size in the same situation.

Just the mere location of a tree can affect its value. For example, if you have a huge elm in the center of your front yard as the centerpiece of your landscape, it is going to be valued much more than the same tree growing in the corner of a parking lot. Just like the value of a home, when it comes to trees an important asset is location, location, location.

The health of a tree is probably the most important factor. Obviously a dead tree has little value in a landscape, so trees that are stressed or dying are going to be of less value than strong, healthy ones. One factor to consider when determining the degree of a tree problem is judging whether or not it is a temporary or a permanent situation. Does it have an insect feeding on its leaves this year or is it infested with borers that will surely kill it? A short-term problem will have a minimal effect on the value of a tree, while more severe problems will decrease the value.

Tree structure is another important factor. A solid tree with good branching is going to be worth more than a tree that has hollows and poor branching, or one that has never been pruned to eliminate or reduce structural deficiencies. Keeping a tree properly maintained can add value and no maintenance or improper pruning such as topping a tree can significantly reduce its value. In fact, topped trees hold little value because the structural integrity of the tree was lost – over time the tree will likely fall apart.

The species of tree will be a major factor in determining worth. A large oak will be worth much more than a Chinese elm of the same size. Species with known problems such as weak structure or disease susceptibility will have a lesser value than those that do not. Volunteer trees such as mulberry, box elder, and tree of heaven are not as valuable as planned specimen trees like beech or Japanese maple.

Yet another factor is availability. If a tree is rare or in high demand it will be harder to find a comparable replacement to help determine its value. I know of a company that had to go to New York to find a suitable replacement for a damaged tree and the cost was well over $20,000 to purchase and move the tree back to Michigan.

So why is it important to put a price tag on trees? It is difficult to sell a large tree and move it, and the demand for this is minimal, so why the fuss for an appraisal? A few reasons come to mind, such as insurance, taxes, vandalism or neglect. If you have many large, mature trees that increase your property value and would be virtually irreplaceable, you can ask your insurance company about possible riders to your homeowners policy that would cover the removal and clean up of a tree if necessary.

With unpredictable storms and the presence of the emerald ash borer, which is killing our ash trees, many of us will be faced with the unplanned loss of a tree. Check with your accountant about IRS casualty loss provisions and find out if you are eligible for any tax deductions as a result.

Then there is the subject of neglectful damage or vandalism to trees. Let’s say a situation gets to the point where a settlement needs to be worked out. If the damaged tree is appraised, the tree’s owner can argue for the real value of the tree instead of settling for some small replacement. Appraisals can be done from old pictures or even stumps, which can tell a lot about the tree’s health and can aid in determining their worth.

Although most of us appreciate the beauty that trees provide us, fewer know the monetary value associated with their trees, and they would be surprised to find out they are so valuable. Maybe this increased awareness can save a few trees from removal and increase the level of care they receive. But to those who hold a sentimental attachment to a favorite tree, the dollar amount placed on it could never replace its loss.

Steve Turner is a Certified Arborist from Arboricultural Services in Oakland County, Michigan.

by Steve Turner

With the huge numbers of ash trees being removed due to the emerald ash borer, many people are experiencing sticker shock when they get estimates to perform the work. I hear it so often, “How come it costs so much to remove this tree?”

The biggest reason is insurance – our industry is a high risk business and we have to pay high premiums just to operate. Our workman’s compensation insurance is up there with coal miners or iron workers. We have to pay close to 25 percent of what an employee earns just for this insurance, and additionally, most companies will have a million dollar liability policy to cover any property damage that may occur in case of an accident.

Also, employees earn skilled labor wages, and the equipment required to be competitive is expensive and needs continuous maintenance or replacement.

Factors that affect the removal cost
So how do tree care companies determine what it costs to complete a job? We estimate time and the cost of disposing the debris. Most companies are charging between $65 and $125 per man hour. While this seems like a big difference, it’s really not because the ones who charge a higher rate often have more equipment and better-trained employees. This allows them to work faster and more efficiently than those with less.

When we are estimating a job, we are looking for things that are going to slow us down removing or trimming the tree, and looking to see how close can we get our equipment to the work site. The most common obstacles are structures, wires, fences and other trees and plants. If we are in tight areas with lots of obstacles, we have to remove the tree in smaller pieces and lower most or all of it to the ground with ropes and rigging devices to avoid any damage. This takes a lot more time than a tree we can let fall into an open area and cut apart on the ground.

Access to the job site is important and the less accessible it is, the higher the price will climb. Sites with limited or no access will take longer to remove the debris and get it to the chipper. The closer we can get the chipper to the work area without causing damage to the lawn the better. Jobs where everything must come through a 36-inch gate or are on the bottom of a steep slope are difficult and often require extra men to keep the debris from backing up under the work area.

Trees that span more than one yard can be tricky. We need to have written permission from the neighbor to access their yard or we have to lower all the debris back to the yard we are working from, which requires more skill and time.

Jobs with no backyard access or those that have large trees over many obstacles, especially houses, will often require the use of a crane. This technique is becoming popular because it reduces the amount of cuts and rigging that has to be done in the tree, which reduces the chance of accidents. If we use a crane, we can attach it to large sections of the tree and make one cut to release it and raise it over the house to the front yard where it can easily be cut up on the ground close to the chipper. So a tree that might take over 100 cuts and lots of rigging with little room for error can be removed in just a few sections and be placed in a more accessible area relatively quickly and safely.

If both the climber and crane operator are skilled in these techniques, a job that would have taken days can be done in hours. This will save the homeowner money and the company is able to reduce the amount of workman’s comp and hourly wage in exchange for the cost of the crane rental. Not all companies are skilled in these techniques and it would be wise to discuss their experience when considering them to perform the work. They will need to accurately judge weight and engineer the proper rigging in order to avoid tipping the crane or losing a load.

The condition of the tree is critical
Another important factor in quoting a tree removal is its condition and structural integrity. Can the tree be climbed or will it have to be done with a bucket? If it can’t be climbed, can we get the right equipment close enough or not? How long has the tree been dead; is it brittle or not? The worst thing you can do is delay removing a dead tree until the bark starts to fall off. If you wait a year or two after it dies it will surely cost you more, assuming it can’t be felled into an open area. Trees that have been dead for more than a year are very hazardous to climb and in many cases impossible to safely remove without the aid of aerial equipment or cranes.

Dead wood does not flex, it just cracks or breaks. When we cut a piece off and it swings down into the trunk or another branch, it explodes into pieces which can cause damage to nearby structures that would normally be out of harm’s way. I have seen pieces of dead trees fly well over a hundred feet upon impact, and trying judge where this debris might go is difficult.

The only advantage that dead trees have is that they weigh much less than live wood since they don’t have all that water in them. If a dead branch were to hit something it would do far less damage than if it were live. Nevertheless, don’t make the mistake of delaying the removal of a dead tree. If you don’t have it taken down in the first year it will cost you more, as well as creating a more hazardous work environment and increasing the chances for accidents.

Winter time is a good time
If your budget is tight, schedule the work for the winter, since most companies will give discounts for off-season work. It is faster to remove trees in the winter because we don’t have to be concerned as much about lawn damage or flower beds. This allows us to remove larger pieces with less rigging, saving us time and you money. Winter is also the best time to prune your trees because insects and disease organisms are dormant and the tree will have plenty of time to seal the wounds before they are active again in the spring. Winter is a slow time for tree companies and most would welcome any additional business at that time, so be smart and take advantage of a good thing for both you and them. The only drawback to winter tree work is scheduling around the weather – sometimes jobs can be delayed due to snow or very cold weather. The shortened daylight can also turn a one-day job into two, but in the end the work will get done and you will likely have more money in your pocket.

Steve Turner is a Certified Arborist from Arboricultural Services in Oakland County, Michigan.

by Steve Turner

This is were the law can get a little gray because removing similar types or amounts of limbs from different species of trees can have different effects. Some species are much more tolerant than others to pruning, and the size and amount that can be safely removed will vary greatly between them. Most shrubs and many smaller ornamental trees will tolerate heavy pruning without damage and would most likely be able to regrow back to their original form if left alone.

On the other hand, if you remove large limbs from medium or mature trees, it is unlikely that the tree will be able to replace them and the loss will be permanent. In some cases this would be tolerable, but if the tree is stressed or in competition with other trees, the heavy pruning could indeed damage it.

Also, the size of the limb is very important. Removing a limb that is very large may cause a wound that will never close, and form a cavity or structural defect in the future. If you cut lower limbs back to the property line and the canopy above shades them, they will most likely die due to lack of sunlight.

Nevertheless, you do have the right to remove any deadwood or hazardous limbs, regardless of size or effect on the tree.

Getting access to the tree
Another issue becomes access. Do you need to enter the tree from the neighbor’s property or can you do the work from your side? Many tree care companies will not work on neighbor’s trees without written permission from the owner. I would suggest that both parties agree on which limbs are to be removed ahead of time and not just leave an open-ended statement saying that any limb that has crossed the property line can be removed. You may come home to find that your expectations have not been met.

Shared trees
A common situation is a tree or any portion of its base that is growing directly on a property line. In this case the tree becomes joint property and both parties must agree to remove or prune the tree before any work is performed. If the tree dies or becomes a hazard, it is the joint responsibility of the owners to remove it and the cost is to be shared between them.

Hazardous trees
Another situation I run into often is when a neighbor has a hazardous tree that is threatening someone else’s property. You cannot force them to remove it unless your city has some type of ordinance that would allow the city to order its removal. Such is the case with many diseased elms and Dutch elm disease. What you can do is have the tree inspected by an arborist and if it is a hazard, the arborist can write a report that clearly states the tree’s defects and why it is hazardous. This can be presented to the owner and if they ignore their responsibility they can potentially be held liable when the tree fails because it is now a known hazard. If the tree were to fall on or damage your property, you can claim it against their insurance and they would have to pay the deductible.

This only applies if the tree is a known hazard – it will not apply to a healthy tree that fails in a storm. That would be considered an act of nature. Even if the tree showed internal decay at the point of failure, without prior knowledge of this defect you would have to claim it on your own insurance and pay the deductible. For a tree to be considered a known hazard it must evaluated by a qualified individual or be obvious to a reasonable person that the tree has a high chance of failure before it fails. An example would be a dead or leaning tree with a large cavity and decay. You would not have to have a prior evaluation in order to claim it as a known hazard because most reasonable people would be able to tell that this is a danger and act accordingly by having it removed. A tree can only be judged a hazard if it has a target under it, such as a structure or object, or is in an area that a person could be present such as a sidewalk, road or playground. A tree in the back forty with no targets and little chance of people being present could not be deemed a hazard no matter what shape it is in or how dead it is.

As an arborist I am always looking for hazard trees and the signs of structural defects whenever I do an estimate because I can potentially be held liable if I visit a property and fail to recognize a hazard and it ends up causing damage in the future. One of the hardest hazards to detect beforehand is root rot on trees because the damage is below ground and can only be seen if the soil around the base of the tree is removed and the roots inspected. Often the only above ground sign we have is the presence of the fruiting bodies of the fungus in the form of mushrooms around the base of the tree or on the roots. If you see any mushrooms or conks on any part of a tree, it would be wise to have the tree checked out by an arborist. These are signs that decay is present and the arborist needs to determine the extent of the decay to see if the tree is safe or needs to be removed.

These are just a few common examples and brief summaries of how the law applies to trees. For more detailed information about these or other questions, check with your insurance agent and/or an attorney about the specifics of your situation.

Steve Turner is a Certified Arborist from Arboricultural Services in Oakland County, Michigan.

by Steve Turner

So now what? We are losing thousands of ash trees to the emerald ash borer (EAB) on our city streets and in our own yards. The big question now is what do we plant to replace them? Everyone wants to know what the best tree is to replace an ash.

When all the elms started dying from Dutch elm disease, the replacement tree of choice was the ash and cities and residents planted them by the thousands to replace all the lost elms. And now three decades later we are once again in same position and everyone is searching for the magic tree that will take the place of the ash.

So what is it? Is it an oak or a maple or maybe a more exotic species like a ginkgo or a Zelkova? Well the answer is easy if we look to the past for a solution. History tells us we are bound to repeat this process over and over again if we seek just one tree. The real answer is all of the above, plus many more types of trees if we want to break this cycle we have been repeating over and over since the demise of the American chestnut in the early 1900’s.

This is a heavily discussed topic among arborists, who all agree that we need diversity in our urban landscapes. We can no longer afford to plant monocultures (single species) on a city block or even one yard.

Another discussion point is the continued heavy use of single cultivars as replacements, as opposed to naturally occurring species. Some in the industry feel that this could lead to problems in the future. One example is the use of ‘Red Sunset’ maples instead of just random native red maples. Their concern is that since all trees of the same cultivar are genetically identical, if one is vulnerable, so are the rest. There is no natural diversity that might make some better able to defend themselves better than others.

This was the case with the ‘Marshall’s Seedless’ green ash. It is by far the most susceptible to the EAB infestation, but on the contrary the ‘Autumn Purple’ white ash seems more resilient than others. So there are pros and cons to each side, but it still is a very valid point that not only do we need to be conscious of species diversity, we also need to be careful about cultivar diversity within the species we plant.

There seems to be a trend among some growers toward collecting native seeds and growing native plants for resale. Hopefully in time there will be more and more of these types of trees available in retail nurseries. We need to educate consumers on the benefits of these native plants and as the demand increases so will our choices. The push to use native species is based on the fact that these trees have evolved in our climate and soil conditions for thousands of years and they will require less care and will be better able to adapt than other species.

In most cases this is true, but we still cannot discount the diversity that the proven introduced species provide us. Trees like gingko, dawn redwood, zelkova, katsura, kousa dogwood, European beech, Chinese lilac and Norway spruce have proven to be as good or better for our urban landscape than some of our native trees.

Others, however, like Norway maple, European birch, purple leaf plum, Colorado blue spruce and Siberian elms, have chronic problems that make them undesirable for southeast Michigan. These trees are either prone to develop girdling roots or are more susceptible to insects or diseases than their native cousins. So while there should be an emphasis on native species (in many cases they will perform better in the long run), we should not ignore using proven introduced species as good alternatives to ash.

Some of the native species I would suggest looking at include red and white oaks. Swamp white oak is very tolerable of poor, compacted soils. Sugar maples are good, but not for street trees where they will be exposed to salt. River birch is a better choice than white birches and is more resistant to borers. Hackberries are very tolerant of poor, compacted soils and will provide a great food source for wildlife without the mess—the birds eat them so fast the fruit will never touch the ground.

Any of the nut-producing trees like walnut, butternut, hickory and beech are very solid trees with few problems and are seldom prone to storm damage. Catalpa, yellowwood, and tulip poplars are all large trees that flower and are very showy when in bloom. Medium-sized trees like hawthorn, redbud, and serviceberry are good choices for smaller lots where space is a concern.

Native trees that are more difficult to find but well worth the effort include paw paw, elder, sassafras, and buckeye. Linden, red maple and honey locust are also native, but have been used so frequently in recent years I would be reluctant to use them in areas where they are already planted in large numbers, for fear that one of them could become the next ash tree. The same thing applies to ornamental pears and crab trees, there are already too many of these trees planted, and trying to find something a little more diverse would be a wise decision for these types of trees.

The best advice I can give you is to do your homework first before you visit the nursery. Know your soil type (clay, loam, or sandy) and whether or not it is compacted (most new subdivisions will have compacted soil). Look at the exposure and sunlight of the planting area, as well as its drainage. And last but not least, drive around your neighborhood to see what types of trees are growing and try to avoid planting the same kind if many of the same species are already there. This way you can help diversify your own area and help avoid the overpopulation of tree species in your neighborhood.

Ash tree replacements

If you need to replace an ash tree or are simply looking for good trees for our region, an excellent guide can be found here: www.hrt.msu.edu/ash.alt.

Steve Turner is a Certified Arborist from Arboricultural Services in Oakland County, Michigan.